Next Article in Journal
Preparation of Micro-Pit-Textured PCD Tools and Micro-Turning Experiment on SiCp/Al Composites
Previous Article in Journal
Cashew Gum: A Review of Brazilian Patents and Pharmaceutical Applications with a Special Focus on Nanoparticles
Previous Article in Special Issue
Precision Layered Stealth Dicing of SiC Wafers by Ultrafast Lasers
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Micromachines
Volume 13
Issue 7
10.3390/mi13071140
micromachines-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Enhanced Deep Ultraviolet Photoresponse in Ga doped ZnMgO Thin Film

by
Mao Ye
1,
Dongbo Wang
2,*,
Shujie Jiao
2 and
Lang Chen
1,*
1
Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
2
Department of Optoelectronic Information Science, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
*
Authors to whom correspondence should be addressed.
Micromachines 2022, 13(7), 1140; https://doi.org/10.3390/mi13071140
Submission received: 15 June 2022 / Revised: 13 July 2022 / Accepted: 15 July 2022 / Published: 19 July 2022
(This article belongs to the Special Issue Emerging Technologies in Wide-Bandgap Semiconductor Devices)
Browse Figures
Versions Notes

Abstract

:
High Mg content (60%) ZnMgO samples with and without Ga dope were grown by an RF magnetron sputtering system. The effect of Ga dope on the ZnMgO sample and the respective ultraviolet photodetectors (UVPD) device’s performance were carefully studied by various experimental methods. The investigations of the structure and optical properties of the ZnMgO sample established that the Ga doped sample has a better crystal quality and larger band gap (5.54 eV). The current-voltage characteristics indicate that both the photocurrent and dark current were enhanced after Ga dope. Under 12 V bias, the undoped UVPD show two spectral response peaks at 244 nm and 271 nm with a responsivity of 1.9 A/W and 0.38 A/W, respectively. While the Ga doped UVPD showed only one response peak at 241 nm and the deep UV responsibility up to 8.9 A/W;, as the bias increased from 12 V to 60 V, the responsiveness raised to 52 A/W, with a signal to noise ratio (241 nm/700 nm) as high as 105. Combining the results of XRD, PL spectrum and XPS, the enhanced ultraviolet photoresponse of the Ga dope device contributed to improving the crystal quality and “dopant-defect pairing effect” caused by Ga doping, which led to a considerable reduction in the number of ionized impurities in the scatting centers, and enhanced the carrier’s mobility. Our work demonstrates that even a high Mg content ZnMgO can exhibit enhanced UV performance after a Ga dope due to the dopant-defect pairing effect, which confirmed the advantage of the use of ZnMgO in the deep-UV region.

1. Introduction

Ultraviolet photodetectors (UVPDs) have wide applications in both civil and military areas, such as space probing, chemical, and biological detection, missile early-warning, flame detecting, biological research, and optical communications [1,2,3,4,5]. Among those semiconductor materials that have a wide band gap (GaN, SiC, diamond, ZnS), ZnO stands out as a promising candidate for UV detection due to its large exciton binding energy (60 meV); direct wide band gap (3.4 eV); environmentally friendly properties; and chemical and thermal stability [6,7,8,9]. Furthermore, the band gap of ZnO can be tailored by forming alloys with other oxides, such as MgO [10], CdO [11], and BeO [12]. In particular, the ZnMgO alloys can enlarge the band gap of ZnO from 3.4 to 7.8 eV, which allows ZnO to work in the deep-UV region and fabricate ZnMgO UVPDs with different cutoff wavelengths by adjusting the Mg content [13,14,15,16]. However, as is well known, ZnO crystallizes and is stabilized in the hexagonal wurtzite lattice, whereas MgO is stabilized in the cubic rock salt lattice. As the Mg content increases, the crystalline structure of ZnMgO ternary alloy will transform through the wurtzite phase (low Mg content), mixed-phase (both hexagonal and cubic phase), and cubic phase (high Mg content) [14,17]. UVPDs based on cubic rock-salt ZnMgO (c-ZnMgO), wurtzite ZnMgO (w-ZnMgO), and mixed-phase ZnMgO (m-ZnMgO) have been reported [18,19,20]. The performance of ZnMgO UVPDs strongly relies on the Mg content; when the Mg concentration is above 33%, ZnMgO ternary alloys are segregated into mixed-phase, and the crystal quality normally decreases with the increase of Mg content and misfit dislocations [21,22]. Furthermore, the conductivities of ZnMgO films usually decrease when the Mg content rises [23,24]. For instance, Matsubara reported that the resistivity of MgZnO varied between 3 × 10−4 Ω cm and 1 × 10−3 Ω cm as the band gap was increased from 3.5 eV to 3.97 eV [24]. Both of them seriously restricted the development of ZnMgO deep-UV optoelectronic devices. Until now, the performance of c-ZnMgO UVPDs (high Mg content) is still worse than “that of w-ZnMgO” (low Mg content) [25].
The performance of ZnMgO UVPDs strongly relies on the Mg content; when the Mg concentration is above 33%, ZnMgO ternary alloys are segregated into mixed-phase, and the crystal quality normally decreases with the increase in Mg content and misfit dislocations [21,22]. Furthermore, the conductivities of ZnMgO films usually decrease when the Mg content rises [23,24]. For instance, Matsubara reported that the resistivity of MgZnO varied between 3 × 10−4 Ω cm and 1 × 10−3 Ω cm as the band gap was increased from 3.5 eV to 3.97 eV [24]. Both of them seriously restricted the development of ZnMgO deep-UV optoelectronic devices. Until now, the performance of c-ZnMgO UVPDs (high Mg content) has been still worse than “that of w-ZnMgO” (low Mg content) [19].
To realize high-performance deep-UV optoelectronic devices, great efforts have been devoted to studying doped ZnMgO [25], such as Dy [26], Ag [27], Al [28], Ga [29], and As [30]. Among these elements, Ga is the most effective n-type dopant in ZnO ascribing to the covalent bond length of Ga-O (1.92 Å) is similar to that of Zn-O (1.97 Å). Meanwhile, the different growth temperatures of ZnO (950 °C) and Ga2O3 (1100 °C) in a vapor–solid progress is conducive to regulating the Ga-doping component [31]. Recently, the first-principle calculation has shown that Ga dope can enhance the electron mobility of ZnO through the dopant-defect pairing effect [32].
Unfortunately, up to now, high Mg content (>50%) Ga doped ZnMgO UVPDs and their optical response performance have been full of challenges and seldom reported.
In this work, we explore the effect of Ga dope on the photoresponse properties of ZnMgO deep-UVPDs. ZnMgO films with and without Ga dope were grown and their respective UVPDs device performances were carefully studied. The Ga doped ZnMgO has a better crystal quality and only one band gap (5.54 eV) compared with the undoped ZnMgO. Enhanced deep-UV photoresponse was found in the Ga-doped UVPDS with a cut-off wavelength of about 241 nm. The mechanism of the enhanced UV photoresponse in Ga-doped ZnMgO alloys was discussed in detail through careful inspections of photoresponse properties, combined with the result of XPS and photoluminescence.

2. Materials and Methods

2.1. Growth of Sample

ZnMgO samples with and without Ga dope were all deposited on quartz substrates through an RF magnetron sputtering system [33] in a vacuum (4.9 × 10−3 Torr) chamber with the same growth condition. Before deposition, the substrates were cleaned with ultrasonic vibration in ethanol and high purity water.
The flow rate of Ar and O2 was 8:32. And the working pressure was 0.5 Pa. For all the samples, the sputtering power was kept at 70 W, and the sputtering time was 120 min. The distance between the sample and target was 10 cm.
The ZnMgO target was prepared by the sintering of a mixture of 99.99% pure MgO and ZnO powders. The target contained 60 at% Mg, and 40 at% Zn. While Ga: ZnMgO target was also prepared by a sintering mixture of 99.99% pure MgO, ZnO, and Ga2O3 powders. The target contained 57 at% Mg, 40 at% Zn, and 3 at% Ga.

2.2. Fabrication of the UVPDs

The metal–semiconductor–metal (MSM) deep-UVPDs were fabricated using the standard semiconductor fabrication techniques, which is a photolithography process employed to pattern the symmetric metal electrode pairs [34,35,36]. The diagrammatic structure of the PEC UVPD is shown in Figure 1a. The interdigital metal electrodes, which were defined on a 200 nm Au layer by the conventional UV photolithography and lift-off procedure, are 500 μm long and 5 μm wide, with a 2 μm gap. Figure 1b shows the schematic full view of the interdigital metal electrodes of the UVPDs, in which the yellow and white parts are the electrode and sample, respectively. There are 80 fingers in our interdigital structure, 40 up and 40 down [37].

2.3. Characterization

All the samples were characterized by using X-ray diffraction (XRD) (Panalytical Empyrean, Eindhoven, The Netherlands), X-ray photoelectron spectroscopy (XPS) (ESCALAB 250Xi, ThermoFisher Scientific, Waltham, MA, USA), Energy Dispersive Spectrometer (EDS) (Quanta 200FEG); photoluminescence (PL) characterizations were recorded in CCD spectroscopy at a fixed excitation intensity by a He-Cd laser line 325 nm (HORIBA, LabRAM HR Evolution, Longjumeau, France). LAMBDA UV/Vis Spectrophotometers 850 measured the optical transmittance and reflectance characterizations. Responsivity measurements were carried out with a spectrograph (Zolix, Omni-3007, Beijing, China), photodetector (Zolix, QE-B3-UV, Beijing, china), and a digital data acquisition system (FS-Pro, KEITHLEY/2400, SW Karl Braun Drive, Beaverton, OR, USA). The light source was provided by a 200 W UV-enhanced Xe lamp (Zolix, Beijing, China).

3. Results and Discussion

The XRD pattern of the samples is shown in Figure 2. The diffraction peaks at about 36.84° originate from c-ZnMgO (111) [38], and the peak located at 42.45° is from c-ZnMgO (200) [21].
For the Ga dope ZnMgO sample, there is only one peak observed, implying that the phase separation has been suppressed. Furthermore, after Ga dope, the intensity of c-ZnMgO (111) increases, which indicates that Ga dope ZnMgO is crystallized with (111)-c ZnMgO prefer orientation. Besides, the (111) c-ZnMgO shifts to 36.95°. According to Bragg’s equation [39]
2dsinθ = nλ
d h k l = a / h 2 + k 2 + l 2
where θ is the diffraction angle, d is the Miller indices, and a is the lattice constant. According to the formulas (1) and (2), the diffraction angle θ is in inverse proportion to the lattice constant a, since the lattice constant of ZnO is larger than the MgO [40], so the diffraction peaks of the c-ZnMgO shifting to the high angle side can be ascribed to the decrease of the lattice constant due to the increase in Mg incorporation. In addition, the full width at half-maximum (FWHM) of the (111) XRD rocking curves was obtained by fitting the XRD diffraction peak curve. The FWHM of the (111) XRD rocking curves are 0.62° and 0.44° for the as-grown and Ga doped samples, respectively. This result implies that the crystal quality of ZnMgO improves after Ga dope.
The composition of ZnMgO is measured by the EDS, XPS as summarized in Table 1. More information about EDS and XPS is shown in the support information.
The XPS spectra is used to measure the Ga content of the sample in Figure 3. The peak located at 21 eV is ascribed to Ga 3d [41], which reflects the Ga-O chemical bonding in Ga2O3
Optical transmittance spectra and reflectance spectra of the samples are shown in Figure 4. It can be seen that both samples have over 70% transmittance in the UV and visible region of 250–600 nm. After doping with Ga, the transmittance edge shifted to a shorter wavelength. In addition, after doping with Ga, the transmittance of ZnMgO was enhanced.
The relation between the transmittance (T) and absorption coefficients (a) can be expressed as [42]:
a = (InT − 1)/d
(ahv)2 = A(hv − Eg)
where A is a constant, d is the thickness of the films, Eg is the band gap of the sample. The band gap of the ZnMgO samples can be estimated from the extrapolation approach shown in Figure 5.
The band gaps are 5.54 eV and 5.20 eV for the Ga doped and undoped ZnMgO films, respectively. After Ga dope the band gap of ZnMgO increases, which indicates an increase in Mg content. The result is consistent with the conclusion of XRD and XPS.
The current-voltage characteristics of the ZnMgO sample with and without Ga dope are measured under dark and UV illumination conditions, respectively. In Figure 6a, under UV illumination, at 5 V bias, the current for undoped and doped ZnMgO UVPD was 0.82 mA and 5.2 mA, respectively. While under dark conditions, the dark current for undoped and doped ZnMgO was 0.62 mA and 3.4 mA, respectively. The results I–V indicate that Ga dope can effectively enhance the current of UVPD.
To test the spectral responsivity of the photodetector, the wavelength selective property was measured in terms of the current signal in the range of 200–800 nm at a 12 V bias, and the results are shown in Figure 7. Photoresponsivity is an important property for photodetector performance, which can directly affect the final device spectral response. For the sample without Ga dope, the UVPD has two obvious spectral responses corresponding to a cutoff wavelength of 271 nm and 244 nm, with a responsivity of 1.32 A/W and 0.38 A/W, respectively. While the Ga doped UVPD, the spectral response at 271 nm disappeared and the deep UV spectral response shifted to 241 nm with photoresponsivity up to 8.9 A/W, a signal-to-noise ratio (241 nm/700 nm) as high as 105, nearly five times that of the undoped one. The inserted figure shows the response varying with bias, as the bias increased from 12 V to 60 V, the responsiveness rose to 52 A/W. The response time before and after Ga doping is 300 ms and 55 ms, respectively. In order to improve the response time, Ga doped samples and Bi2Se3 were used to prepare the heterojunction, and the response time of the detector reached 98 μs (Figure 8).
The spectral response results indicate that Ga dope could make the high Mg content (60%) ZnMgO UVPDs obtain a single cut-off wavelength response in the deep ultraviolet region, and enlarge the cut-off wavelength (band gap) of the ZnMgO. This is consistent with the XRD result that Ga dope can suppress the phase separation and improve the crystal quality of the high-Mg-content ZnMgO work in deep-UV regions.
In order to further explore the mechanism of the enhanced spectral response, the cut-off wavelength, carrier concentration, and electron mobility of the ZnMgO samples were measured by Hall effect measurement and listed in Table 2. The cut-off wavelength was obtained by measuring the spectral response cut-off band edge position.
It is worth noting that the carrier concentrates and electron mobility of the ZnMgO sample were both enhanced after Ga dope. Usually, due to grain barrier limited transport [43,44], the electron mobility decreases with the increase of the carrier concentration.
The situation here is similar to the dopant-defect pairing effect calculated through density functional theory (DFT) in Al, Ga doped ZnO [32,45,46].
As they are calculated, Zn vacancies (VZn) lead to reduced electron mobility in the ZnO which act as the additional ionized impurity scattering centers [47]. Due to oppositely charging, defects tend to form pairs and complexes [48]; the Vzn and intentional GaZn+ dopant are finally formed singly charged (GaZn-VZn)− and the charge-neutral (2GaZn-VZn)− defect clusters [49,50], lead to reducing considerably the number of ionized impurities in the scatting centers and enhance the mobility.
The PL spectrum is used to characterize the change in VZn before and after Ga dope (Figure 9). It was observed that there are two obvious emission peaks in the visible region. According to the previous reports, the emission located at 530 nm belongs to VZn [51,52] and the other emission peaks are ascribed to the excess oxygen on the ZnO surface [53,54,55]. As can be seen from Figure 9, the Vzn related emission decreases after Ga doping, which may reduce the number of Vzn.
Furthermore, the binding energy of (GaZn-VZn)− calculated by the DFT method is 3.05 eV (λ = 1.24/Eg, 406 nm) [32]. Meanwhile, in the XPS spectrum (Figure 10), the Ga doped sample emerges at an obvious peak at 409 nm, which is similar to the calculated value. These results indicated that (GaZn-VZn)− exist in ZnMgO after doping with Ga.
Therefore, it is reasonable to conclude that Ga dope in high Mg content ZnMgO films would enhance ultraviolet photoresponse due to the dopant-defect pairing effect.
Combined with the above results, Ga’s role in influencing the performance of the device was elaborated in detail. Firstly, Ga dope can improve the crystal quality of MgZnO, thereby improvingthe photocurrent of the device. Secondly, in the ZnMgO alloys, the formation of acceptor-like compensating intrinsic defects, such as zinc vacancies (VZn), always increases with the rise of Mg content, which reduces the free electron concentration and decreases the mobility through ionized impurity scattering. After being Ga doped, the Vzn and intentional GaZn+ dopant can finally form singly charged (GaZn-VZn)− and the charge-neutral (2GaZn-VZn)− defect clusters, which reduces considerably the number of ionized impurities in the scatting centers, and enhances the carrier’s mobility. An increase in the carrier’s mobility enhances the conductivity of the material and improves the device’s performance.

4. Conclusions

In summary, the effect of Ga dope on the ZnMgO films and the respective UVPD-device performance was carefully studied by various experimental methods, and the mechanism of the enhanced spectral response was explored. The Ga doped sample shows a single c-ZnMgO (111) diffraction peak and narrow FWHM, which indicates that Ga dope can improve the crystal quality of ZnMgO. Under the same bias, the photocurrent of UVPD was significantly enhanced after Ga dope. Under 5 V bias, the undoped UVPD showed two spectral response peaks at 244 nm and 271 nm, while the Ga dope UVPD showed only one response peak at 241 nm and enhanced the deep-UV responsibility. Combining the results of XRD, PL spectrum, and XPS, the enhanced ultraviolet photoresponse of the Ga dope device contributedto improving the crystal quality and “dopant-defect pairing effect” caused by Ga doping, which leads to a considerable reduction in the number of ionized impurities in the scatting centers, and enhances the carrier’s mobility. Our work demonstrates that even a high Mg content ZnMgO can exhibit enhanced UV performance after Ga dope, which confirms the advantage of ZnMgO in the deep-UV regions.

Author Contributions

Conceptualization, L.C.; methodology, D.W.; investigation, M.Y.; resources, D.W., S.J. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Science and Technology Research Items of Shenzhen (JCYJ20180504165650580, and JCYJ20190809142603695).

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Liu, X.; Gu, L.L.; Zhang, Q.P.; Wu, J.Y.; Long, Y.Z.; Fan, Z.Y. All-printable band-edge modulated ZnO nanowire photodetectors with ultra-high detectivity. Nat. Commun. 2014, 5, 4007. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  2. Li, P.G.; Shi, H.Z.; Chen, K.; Guo, D.Y.; Cui, W.; Zhi, Y.S.; Wang, S.L.; Wu, Z.P.; Chen, Z.W.; Tang, W.H. Construction of GaN/Ga2O3 p-n junction for an extremely high responsivity self-powered UV photodetector. J. Mater. Chem. C 2017, 5, 10562. [Google Scholar] [CrossRef]
  3. Bera, A.; Basak, D. Photoluminescence and Photoconductivity of ZnS-Coated ZnO Nanowires. ACS Appl. Mater. Interfaces 2010, 2, 408. [Google Scholar] [CrossRef] [PubMed]
  4. Lu, J.F.; Xu, C.X.; Dai, J.; Li, J.T.; Wang, Y.Y.; Lin, Y.; Li, P.L. Improved UV photoresponse of ZnO nanorod arrays by resonant coupling with surface plasmons of Al nanoparticles. Nanoscale 2015, 7, 3396. [Google Scholar] [CrossRef]
  5. Zhang, B.K.; Wang, D.B.; Jiao, S.J.; Xu, Z.K.; Liu, Y.X.; Zhao, C.C.; Pan, J.W.; Liu, D.H.; Liu, G.; Jiang, B.J.; et al. TiO2-X mesoporous nanospheres/BiOI nanosheets S-scheme heterostructure for high efficiency, stable and unbiased photocatalytic hydrogen production. Chem. Eng. J. 2022, 446, 137138. [Google Scholar] [CrossRef]
  6. Jiao, S.J.; Lu, Y.M.; Zhang, Z.Z.; Li, B.H.; Yao, B.; Zhang, J.Y.; Zhao, D.X.; Shen, D.Z.; Fan, X.W. Optical and electrical properties of highly nitrogen-doped ZnO thin films grown by plasma-assisted molecular beam epitaxy. J. Appl. Phys. 2007, 102, 113509. [Google Scholar] [CrossRef] [Green Version]
  7. Flemban, T.H.; Haque, M.A.; Ajia, I.; Alwadai, N.; Mitra, S.; Wu, T.; Roqan, I.S. A Photodetector Based on p-Si/n-ZnO Nanotube Heterojunctions with High Ultraviolet Responsivity. ACS Appl. Mater. Interface 2017, 9, 37120–37127. [Google Scholar] [CrossRef]
  8. Pung, S.Y.; Choy, K.L.; Hou, X.; Shan, C.X. Preferential growth of ZnO thin films by the atomic layer deposition technique. Nanotechnology 2008, 19, 435609. [Google Scholar] [CrossRef]
  9. Lin, Y.; Liu, J.L.; Shi, J.J.; Zeng, T.; Shan, X.Y.; Wang, Z.Q.; Zhao, X.N.; Xu, H.Y.; Liu, Y.C. Nitrogen-induced ultralow power switching in flexible ZnO-based memristor for artificial synaptic learning. Appl. Phys. Lett. 2021, 118, 103502. [Google Scholar] [CrossRef]
  10. Han, S.; Shao, Y.K.; Lu, Y.M.; Cao, P.J.; Liu, W.J.; Zeng, Y.X.; Jia, F.; Zhu, D.L.; Ma, X.C. Effect of different migration energy for reaction atoms on growth orientation and optical absorption characteristics of cubic MgZnO thin films under different pressure by PLD method. J. Cryst. Growth 2014, 408, 125–128. [Google Scholar] [CrossRef]
  11. Zuniga-Perez, J. ZnCdO: Status after 20 years of research. Mat. Sci. Semicon. Proc. 2017, 69, 36–43. [Google Scholar] [CrossRef]
  12. Shi, H.L.; Duan, Y. Band-gap bowing and p-type doping of (Zn, Mg, Be)O wide-gap semiconductor alloys: A first-principles study. Eur. Phys. J. B 2008, 66, 439–444. [Google Scholar] [CrossRef] [Green Version]
  13. Hou, Y.N.; Mei, Z.X.; Liang, H.L.; Ye, D.Q.; Gu, C.Z.; Du, X.L. Dual-band MgZnO ultraviolet photodetector integrated with Si. Appl. Phys. Lett. 2013, 102, 153510. [Google Scholar] [CrossRef] [Green Version]
  14. Yang, J.L.; Liu, K.W.; Shen, D.Z. Recent progress of ZnMgO ultraviolet photodetector. Chin. Phys. B 2017, 26, 047308. [Google Scholar] [CrossRef]
  15. Zhu, Y.; Liu, K.; Wang, X.; Yang, J.; Chen, X.; Xie, X.; Li, B.; Shen, D. Performance improvement of a ZnMgO ultraviolet detector by chemical treatment with hydrogen peroxide. J. Phys. Chem. C 2017, 5, 7598–7603. [Google Scholar] [CrossRef]
  16. Ma, S.; Feng, S.L.; Kang, S.; Wang, F.; Fu, X.; Lu, W.Q. A High Performance Solar-Blind Detector Based on Mixed-Phase Zn0.45Mg0.55O Alloy Nanowires Network. Electron. Mater. Lett. 2019, 15, 303–313. [Google Scholar] [CrossRef]
  17. Borkovska, L.; Khomenkova, L.; Markevich, I.; Osipyonok, M.; Kolomys, O.; Rarata, S.; Oberemok, O.; Gudymenko, O.; Kryvko, A.; Strelchuk, V. The effect of high temperature annealing on the photoluminescence of ZnMgO alloys. Phys. Status Solidi A 2018, 215, 1800250. [Google Scholar] [CrossRef]
  18. Chen, H.Y.; Yu, P.P.; Zhang, Z.Z.; Teng, F.; Zheng, L.X.; Hu, K.; Fang, X.S. Ultrasensitive self-powered solar-blind deep-ultraviolet photodetector based on all-solid-state polyaniline/MgZnO bilayer. Small 2016, 12, 5809–5816. [Google Scholar] [CrossRef]
  19. Fan, M.M.; Liu, K.W.; Chen, X.; Wang, X.; Zhang, Z.Z.; Li, B.H.; Shen, D.Z. Mechanism of excellent photoelectric characteristics in mixed-phase ZnMgO ultraviolet photodetectors with single cutoff wavelength. ACS Appl. Mater. Interface 2015, 7, 20600–20606. [Google Scholar] [CrossRef]
  20. Wang, R.C.; Lin, Y.X.; Wu, J.J. Intrinsic n-and p-Type MgZnO nanorods for deep-UV detection and room-temperature gas sensing. J. Phys. Chem. C 2015, 119, 29186–29192. [Google Scholar] [CrossRef]
  21. Takeuchi, I.; Yang, W.; Chang, K.S.; Aronova, M.A.; Venkatesan, T. Monolithic multichannel ultraviolet detector arrays and continuous phase evolution in composition spreads. J. Appl. Phys. 2003, 94, 7336. [Google Scholar] [CrossRef]
  22. Xie, W.Z.; Wang, D.B.; Guo, F.Y.; Liu, T.R.; Jiao, S.J.; Wang, J.Z.; Gao, S.Y.; Yu, Q.J.; Zhang, Y.; Luan, C.Y.; et al. The effect of annealing temperature on the optical and electrical properties of cubic MgZnO films grown by RF magnetron sputtering. J. Mater. Sci. 2017, 28, 1644. [Google Scholar] [CrossRef]
  23. Matsubara, K.; Tampo, H.; Shibata, H.; Yamada, A.; Fons, P.; Iwata, K.; Niki, S. Band-gap modified Al-doped transparent conducting films deposited by pulsed laser deposition. Appl. Phys. Lett. 2004, 85, 1374. [Google Scholar] [CrossRef]
  24. Wei, W.; Jin, C.M.; Narayan, J.; Narayan, R.J. Optical and electrical properties of gallium-doped MgxZn1-xO. J. Appl. Phys. 2010, 107, 013510. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  25. Jiang, M.M.; He, G.H.; Chen, H.Y.; Zhang, Z.Z.; Zheng, L.X.; Shan, C.X.; Shen, D.Z.; Fang, X.S. Wavelength-Tunable Electroluminescent Light Sources from Individual Ga-Doped ZnO Microwires. Small 2017, 13, 1604034. [Google Scholar] [CrossRef] [PubMed]
  26. Kumar, P.; Singh, R.; Pandey, P.C. Enhanced ultraviolet photo-response in Dy doped ZnO thin film. J. Appl. Phys. 2018, 123, 054502. [Google Scholar] [CrossRef]
  27. Cao, L.; Zhu, L.P.; Jiang, J.; Li, Y.; Zhang, Y.Z.; Ye, Z.Z. Preparation and properties of p-type Ag-doped ZnMgO thin films by pulsed laser deposition. J. Alloys Compd. 2012, 516, 157. [Google Scholar] [CrossRef]
  28. Yoon, J.G.; Cho, S.W.; Choi, W.S.; Kim, D.Y.; Chang, H.; Kim, C.O.; Lee, J.; Jeon, H.; Choi, S.H.; Noh, T.W. Electroluminescence from n–n isotype heterostructures of graded-band-gap ZnMgO: Al and ZnO films on platinized Si. J. Phys. D Appl. Phys. 2011, 44, 41. [Google Scholar] [CrossRef]
  29. Cuong, H.B.; Lee, C.S.; Jeong, S.H.; Lee, B.T. Realization of highly conductive Ga-doped ZnO film with abnormally wide band-gap using magnetron sputtering by simply lowering working pressure. Acta. Mater. 2017, 130, 47–55. [Google Scholar] [CrossRef]
  30. Przezdziecka, E.; Lisowski, W.; Reszka, A.; Kozznecki, A. Evidence of magnesium impact on arsenic acceptor state: Study of ZnMgO:As molecular beam epitaxy layers. Appl. Surf. Sci. 2018, 435, 676. [Google Scholar] [CrossRef]
  31. Liu, Y.; Jiang, M.M.; He, G.H.; Li, S.F.; Zhang, Z.Z.; Li, B.H.; Zhao, H.F.; Shan, C.X.; Shen, D.Z. Wavelength-Tunable Ultraviolet Electroluminescence from Ga-Doped ZnO Microwires. ACS Appl. Mater. Interface 2017, 9, 40743. [Google Scholar] [CrossRef] [PubMed]
  32. Sky, T.N.; Johansen, K.M.; Rise, H.N.; Svensson, B.G.; Vines, L. Gallium diffusion in zinc oxide via the paired dopant-vacancy mechanism. J. Appl. Phys. 2018, 123, 055701. [Google Scholar] [CrossRef]
  33. Ali, A.; Wang, D.B.; Wang, J.Z.; Jiao, S.J.; Guo, F.Y.; Zhang, Y.; Gao, S.Y.; Ni, S.M.; Wang, D.Z.; Zhao, L.C. ZnO nanorod arrays grown on an AlN buffer layer and their enhanced ultraviolet emission. Crystengcomm 2017, 19, 6085. [Google Scholar] [CrossRef]
  34. Zeng, Z.; Wang, D.B.; Wang, J.Z.; Jiao, S.J.; Liu, D.H.; Zhang, B.K.; Zhao, C.C.; Liu, Y.Y.; Liu, Y.X.; Xu, Z.K.; et al. Broadband Detection Based on 2D Bi2Se3/ZnO Nanowire Heterojunction. Crystals 2021, 11, 169. [Google Scholar] [CrossRef]
  35. Song, X.-X.; Liu, D.; Mosallanejad, V.; You, J.; Han, T.-Y.; Chen, D.-T.; Li, H.-O.; Cao, C.; Xiao, M.; Guo, G.-C.; et al. A gate defined quantum dot on the two-dimensional transition metal dichalcogenide semiconductor WSe2. Nanoscale 2015, 7, 16867–16873. [Google Scholar] [CrossRef] [Green Version]
  36. Xu, H.Z.; Wang, Z.G.; Kawabeb, M.; Harrisond, I.; Ansellc, B.J.; Foxonc, T. Fabrication and characterization of metal–semiconductor–metal (MSM) ultraviolet photodetectors on undoped GaN/sapphire grown by MBE. J. Cryst. Growth 2015, 7, 16867–16873. [Google Scholar] [CrossRef]
  37. Wang, D.B.; Jiao, S.J.; Sun, S.J.; Zhao, L.C. Al0.40In0.02Ga0.58N based metal-semiconductor-metal photodiodes for ultraviolet detection. In Proceedings of the 2012 International Conference on Optoelectronics and Microelectronics, Changchun, China, 23–25 August 2012; p. 412. [Google Scholar]
  38. Fan, M.M.; Liu, K.W.; Chen, X.; Zhang, Z.Z.; Li, B.H.; Zhao, H.F.; Shen, D.Z. Realization of cubic ZnMgO photodetectors for UVB applications. J. Mater. Chem. C 2015, 3, 313. [Google Scholar] [CrossRef]
  39. Zhong, M.; Li, Y.; Tariq, M.; Hu, Y.M.; Li, W.X.; Zhu, M.Y.; Jin, H.M.; Li, Y.B. Effect of oxygen vacancy induced by pulsed magnetic field on the room-temperature ferromagnetic Ni-doped ZnO synthesized by hydrothermal method. J. Alloys Compd. 2016, 675, 286–291. [Google Scholar] [CrossRef]
  40. Zhu, Y.Z.; Chen, G.D.; Ye, H.G. Electronic structure and phase stability of MgO, ZnO, CdO, and related ternary alloys. Phys. Rev. B 2008, 77, 245209. [Google Scholar] [CrossRef] [Green Version]
  41. Cossu, G.; Ingo, G.M.; Mattogno, G.; Padeletti, G.; Proietti, G.M. XPS investigation on vacuum thermal desorption of UV/ozone treated GaAs(100) surfaces. Appl. Surf. Sci. 1992, 56–58, 81. [Google Scholar] [CrossRef]
  42. Yu, J.H.; Kim, J.H.; Jeong, T.S.; Akhtar, M.S.; Youn, C.J.; Hong, K.J. Study on the Structural and Optical Properties of Cd1-xZnxO Layers Enhanced by Rapid Thermal Annealing. Electron. Mater. Lett. 2011, 7, 215. [Google Scholar] [CrossRef]
  43. Godlewskiab, M.; Guziewicza, E.; Łukaa, G.; Krajewskia, T.; Łukasiewiczab, M.; Wachnickiab, Ł.; Wachnickaab, A.; Kopalkoa, K.; Saremc, B.; Dalatic, A. ZnO layers grown by Atomic Layer Deposition: A new material for transparent conductive oxide. Thin Solid Films 2009, 518, 1145. [Google Scholar] [CrossRef]
  44. Ellmer, K.; Mientus, R. Carrier transport in polycrystalline ITO and ZnO: Al II: The influence of grain barriers and boundaries. Thin Solid Films 2008, 516, 5829. [Google Scholar] [CrossRef] [Green Version]
  45. Steiauf, D.; Lyons, J.L.; Janotti, A.; Van de Walle, C.G. First-principles study of vacancy-assisted impurity diffusion in ZnO. Appl. Mater. 2014, 2, 096101. [Google Scholar] [CrossRef] [Green Version]
  46. Johansen, K.M.; Vines, L.; Bjorhein, T.S.; Schifano, R.; Svensson, B.G. Aluminum Migration and Intrinsic Defect Interaction in Single-Crystal Zinc Oxide. Phys. Rev. Appl. 2015, 3, 024003. [Google Scholar] [CrossRef] [Green Version]
  47. Ke, Y.; Lany, S.; Berry, J.J.; Perkins, J.D.; Parilla, P.A.; Zakutayev, A.; Ohno, T.; O’Hayre, R.; Ginley, D.S. Enhanced electron mobility due to dopant-defect pairing in conductive ZnMgO. Adv. Funct. Mater. 2014, 24, 2875. [Google Scholar] [CrossRef]
  48. Kroger, F.A. The Chemistry of Imperfect Crystals Noth-Holland; Elsevier: Amsterdam, The Netherlands, 1974. [Google Scholar]
  49. Demchenko, D.O.; Earles, B.; Liu, H.Y.; Avrutin, V.; Izyumskaya, N.; Ozgur, U.; Morkoc, H. Impurity complexes, and conductivity of Ga-doped ZnO. Phys. Rev. B 2011, 84, 075201. [Google Scholar] [CrossRef] [Green Version]
  50. Tuomisto, F.; Ranki, V.; Saarinen, K.; Look, D.C. Evidence of the Zn Vacancy Acting as the Dominant Acceptor in -Type ZnO. Phys. Rev. Lett. 2003, 91, 205502. [Google Scholar] [CrossRef] [Green Version]
  51. Fang, H.B.; Yang, S.Y.; Zhang, P.F.; Wei, H.Y.; Liu, X.L.; Jiao, C.M.; Zhu, Q.S.; Chen, Y.H.; Wang, Z.G. Investigation of oxygen vacancy and interstitial oxygen defects in ZnO films by photoluminescence and X-ray photoelectron spectroscopy. Chin. Phys. Lett. 2007, 24, 2108. [Google Scholar]
  52. Coleman, V.A.; Bradby, J.E.; Jagadish, C. Observation of enhanced defect emission and excitonic quenching from spherically indented ZnO. Appl. Phys. Lett. 2006, 89, 082102. [Google Scholar] [CrossRef] [Green Version]
  53. Pan Gray, B.; Aslam, M.; Misra, D.S.; Ghosh, M.; Bahadur, D. Defect-Related Emissions and Magnetization Properties of ZnO Nanorods. Adv. Funct. Mater. 2010, 20, 1161. [Google Scholar] [CrossRef]
  54. Vlasenko, L.S.; Watkins, G.D. Optical detection of electron paramagnetic resonance in room-temperature electron-irradiated ZnO. Phys. Rev. B 2005, 71, 125210. [Google Scholar] [CrossRef]
  55. Bandopadhyay, K.; Mitra, J. Zn interstitials and O vacancies responsible for ntype ZnO: What do the emission spectra reveal? RSC Adv. 2015, 5, 23540–23547. [Google Scholar] [CrossRef]
Micromachines 13 01140 g001 550
Figure 1. (a) The diagrammatic structure of the UVPDs, (b) The schematic full view of the interdigital metal electrodes of the UVPDs.
Figure 1. (a) The diagrammatic structure of the UVPDs, (b) The schematic full view of the interdigital metal electrodes of the UVPDs.
Micromachines 13 01140 g001
Micromachines 13 01140 g002 550
Figure 2. The XRD pattern of the ZnMgO sample with and without Ga dope.
Figure 2. The XRD pattern of the ZnMgO sample with and without Ga dope.
Micromachines 13 01140 g002
Micromachines 13 01140 g003 550
Figure 3. XPS survey spectrum of the ZnMgO sample with and without Ga dope.
Figure 3. XPS survey spectrum of the ZnMgO sample with and without Ga dope.
Micromachines 13 01140 g003
Micromachines 13 01140 g004 550
Figure 4. Optical properties of ZnMgO samples with and without Ga dope.
Figure 4. Optical properties of ZnMgO samples with and without Ga dope.
Micromachines 13 01140 g004
Micromachines 13 01140 g005 550
Figure 5. The curve of (ahv)2 versus hv for ZnMgO samples.
Figure 5. The curve of (ahv)2 versus hv for ZnMgO samples.
Micromachines 13 01140 g005
Micromachines 13 01140 g006 550
Figure 6. The current-voltage curve of the ZnMgO sample. (a) as grown and (b) with Ga dope.
Figure 6. The current-voltage curve of the ZnMgO sample. (a) as grown and (b) with Ga dope.
Micromachines 13 01140 g006
Micromachines 13 01140 g007 550
Figure 7. Spectral response of the ZnMgO sample with and without Ga dope.
Figure 7. Spectral response of the ZnMgO sample with and without Ga dope.
Micromachines 13 01140 g007
Micromachines 13 01140 g008 550
Figure 8. Response time of the detector.
Figure 8. Response time of the detector.
Micromachines 13 01140 g008
Micromachines 13 01140 g009 550
Figure 9. PL spectra of the ZnMgO sample at room temperature.
Figure 9. PL spectra of the ZnMgO sample at room temperature.
Micromachines 13 01140 g009
Micromachines 13 01140 g010 550
Figure 10. XPS survey spectrum of the ZnMgO samples.
Figure 10. XPS survey spectrum of the ZnMgO samples.
Micromachines 13 01140 g010
Table
Table 1. Structure properties of ZnMgO sample.
Table 1. Structure properties of ZnMgO sample.
SampleComposition (EDS)Composition (XPS)FWHM
Ga undope sampleZn0.46Mg0.54OZn0.46Mg0.54O0.62°
Ga dope sampleZn0.39Mg0.58Ga0.03OZn0.41Mg0.57Ga0.02O0.44°
Table
Table 2. The electrical properties of the sample.
Table 2. The electrical properties of the sample.
SampleCut-Off Wave-LengthCarrier Concen-Trate (1016 cm−3)Electron
Mobility
(cm2/V∙s)		T
Ga dope sample241 nm2.876.73N
Ga undope sample244 nm0.192.26N
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Ye, M.; Wang, D.; Jiao, S.; Chen, L. Enhanced Deep Ultraviolet Photoresponse in Ga doped ZnMgO Thin Film. Micromachines 2022, 13, 1140. https://doi.org/10.3390/mi13071140

AMA Style

Ye M, Wang D, Jiao S, Chen L. Enhanced Deep Ultraviolet Photoresponse in Ga doped ZnMgO Thin Film. Micromachines. 2022; 13(7):1140. https://doi.org/10.3390/mi13071140

Chicago/Turabian Style

Ye, Mao, Dongbo Wang, Shujie Jiao, and Lang Chen. 2022. "Enhanced Deep Ultraviolet Photoresponse in Ga doped ZnMgO Thin Film" Micromachines 13, no. 7: 1140. https://doi.org/10.3390/mi13071140

APA Style

Ye, M., Wang, D., Jiao, S., & Chen, L. (2022). Enhanced Deep Ultraviolet Photoresponse in Ga doped ZnMgO Thin Film. Micromachines, 13(7), 1140. https://doi.org/10.3390/mi13071140

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop