The Effect of Interlayer Microstructure on the Thermal Boundary Resistance of GaN-on-Diamond Substrate
Round 1
Reviewer 1 Report
The authors report the effect of silicon nitride periodic structures on the thermal boundary resistance of GaN/polycrystalline diamond structure. In the research, the authors performed fabrication of SiNx deposition, electron microscopy observation, and TDTR measurements. Overall, the authors' conclusion is supported by the results though diamond growth behavior can be another factor affecting TBR. However, the manuscript's quality can be improved by revision including the followings:
- Typos, inconsistent terms, and wrong term: Prei vs. Peri., incestigated, adsorption (the authors may want to discuss adhesion), etc..
- How did the authors fabricate the periodic structure? Figure 1 shows that the SiNx periodic structure has regular arrays but Figure 3(b) doesn't support a regular arrangement. According to the authors' description, the periodic structure was prepared by Ar ion bombardment, which may not be useful to fabricate a periodic structure. The authors need to describe the sample preparation procedure in detail. If the SiNx structure was not periodic, the authors need to revise Figure 1(b).
- A cleaning procedure of GaN surfaces before and after SiN deposition needs to be described because magnetron sputtering of SiN on GaN can induce damage under certain conditions. If there was a potential concern on the surfaces of GaN, blocking accurate TDTR measurements and analyses, the authors should discuss it. If the authors didn't do any cleaning, the authors had better mention it.
- In Figure 3, where is the GaN layer?
- The authors prepared 80, 100 nm-thick SiN layers to study TBR of their structures. However, the authors also discussed that thinner (as thin as 5-20 nm) interlayer lowers TBR. If so, why did the authors choose 80, 100 nm-thick layers not 20-50 nm-thick ones? The rationale needs to be included.
Author Response
Dear Reviewer,
Firstly, we would like to show our sincere thanks and respect for your comments and suggestions on our manuscript. All the information you described in the review letter is very useful and valuable to us.
Response to your comments and suggested revisions are listed and answered one by one as follows:
Review 1：
The authors report the effect of silicon nitride periodic structures on the thermal boundary resistance of GaN/polycrystalline diamond structure. In the research, the authors performed fabrication of SiNx deposition, electron microscopy observation, and TDTR measurements. Overall, the authors' conclusion is supported by the results though diamond growth behavior can be another factor affecting TBR. However, the manuscript's quality can be improved by revision including the followings:
Comment-1：Typos, inconsistent terms, and wrong term: Prei vs. Peri., incestigated, adsorption (the authors may want to discuss adhesion), etc..
Response: Thank you very much for your comments. Spelling mistakes in the text have been corrected, please find the corresponding changes in the revised manuscript with yellow highlights.
Comment-2：How did the authors fabricate the periodic structure? Figure 1 shows that the SiNx periodic structure has regular arrays but Figure 3(b) doesn't support a regular arrangement. According to the authors' description, the periodic structure was prepared by Ar ion bombardment, which may not be useful to fabricate a periodic structure. The authors need to describe the sample preparation procedure in detail. If the SiNx structure was not periodic, the authors need to revise Figure 1(b).
Response: The SiNx periodic structure is obtained by inductively coupled plasma etching (ICP) combined with precise mask control method, the process parameters is shown in the table below. Figure 3 shows that SiNx is not a periodic structure due to the etching of SiNx by hydrogen plasma during the diamond deposition process, and its periodicity suffers a certain degree of damage. We have supplemented the etching process in detail, please find the corresponding changes in the revised manuscript with yellow highlights.
Table1 SiNx etching process parameters
|
Material |
ICP/W |
RF/W |
Chamber pressure/Pa |
O2/sccm |
Ar/sccm |
SF6/sccm |
|
SiNx |
100 |
10 |
1 |
5 |
10 |
10 |
Comment-3：A cleaning procedure of GaN surfaces before and after SiN deposition needs to be described because magnetron sputtering of SiN on GaN can induce damage under certain conditions. If there was a potential concern on the surfaces of GaN, blocking accurate TDTR measurements and analyses, the authors should discuss it. If the authors didn't do any cleaning, the authors had better mention it.
Response: Thank you for providing us with so many useful references. A cleaning procedure of GaN surfaces before and after SiN deposition is shown as follows. The substrates are ultrasonically cleaned with acetone and ethanol for 5 min successively, then rinsed with deionized water. To ensure that the GaN surface is clean. Corresponding changes has been made in the revised manuscript with yellow highlights in the Experimental Details.
Comment-4：In Figure 3, where is the GaN layer?
Response: Dear reviewer, thank you so much for your remind and constructive suggestions. We have annotated GaN in Figure 3 in the revised manuscript.
Comment-5：The authors prepared 80, 100 nm-thick SiN layers to study TBR of their structures. However, the authors also discussed that thinner (as thin as 5-20 nm) interlayer lowers TBR. If so, why did the authors choose 80, 100 nm-thick layers not 20-50 nm-thick ones? The rationale needs to be included.
Response: Dear reviewer, thank you so much for your remind and constructive suggestions. We use the 100nm-thick SiNx layer that is quite thick compared to a SiNx layer with a thickness of 20-50nm. Since GaN is susceptible to etching in diamond deposition environment. In order to avoid being partially etched in plasma, the thickness of SiNx layer is increased to 100 nm (make sure it is compact and crackless). We have supplemented this part in the revised manuscript.
In addition, 80nm and 100nm SiNx are chose to exclude the effect of the seemingly thinning of SiNx thickness caused by the periodic structure on the thermal boundary resistance of GaN-on-diamond. This is mentioned in the original manuscript. please find the line 113, page and line 178-184, page 5.
Thank you again for your valuable suggestions and comments. We hope our response to the review is appropriate and correct.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors, I have carefully read your paper entitled "The effect of interlayer microstructure on the thermal boundary resistance of GaN/diamond substrate". I believe the article is acceptable for publication after rewriting the manuscript according to the questions or proposals posed below:
1. Some correction of English language is required:
- In the Abstract section, the sentence on page 1, line 14:
„Combination with time-domain thermoreflectance measurement and microstructural analysis, the TBReff, Dia/GaN is dominated by the microstructure of the SiNx interlayer, which effect the diamond growth seeding and the diamond nucleation surface.”
should be improved in a following way:
Combination with time-domain thermoreflectance measurement and microstructural analysis, the TBReff, Dia/GaN is dominated by the microstructure of the SiNx interlayer, which effects the diamond growth seeding and the diamond nucleation surface.
- In the Introduction section, the sentence on page 1, line 26:
„With increasing power density and decreasing size of GaN-based electronic power devices that the heat dissipation has become a key problem for practical applications.”
should be improved in a following way:
With increasing power density and decreasing size of GaN-based electronic power devices, heat dissipation has become a key problem for practical applications.
- In the Introduction section, the sentence on page 1, line 39:
„The important parameters of the devices are hinghly dependent on thethermal management technology of the device, such as gain, saturated power and maximum frequency.”
should be improved in a following way:
The important parameters of the devices are highly dependent on the thermal management technology of the device, such as gain, saturated power and maximum frequency.
- In the Introduction section, the sentence on page 2, line 72:
„Therefore, the SiNx film is introduced as the interlayer to relieve the problems of thermal expamsion coefficients and lattic mismatch between on the GaN and diamond.”
should be improved in a following way:
Therefore, the SiNx film is introduced as the interlayer to relieve the problems of thermal expansion coefficients and lattice mismatch between the GaN and diamond.
- In the Introduction section, the sentence on page 2, line 91:
„The purpose of this study is to better understand interfacial layers and structure design of SiNx interlayer play a significant role in enhancing thermal transport in GaN-on-diamond devices through decreasing TBReff, Dia/GaN of the interface.”
should be improved in a following way:
The purpose of this study is to better understand the interfacial layers and structure design of the SiNx interlayer, which play a significant role in enhancing thermal transport in GaN-on-diamond devices through decreasing TBReff, Dia/GaN of the interface.
- In the Experimental Details section, the sentence on page 3, line 107:
„Finally, a polycrystalline diamond layer with a thickness of about 2 μm is grown on the surface of GaN/SiNx by microwave plasma CVD systema.”
should be improved in a following way:
Finally, a polycrystalline diamond layer with a thickness of about 2 μm is grown on the surface of GaN/SiNx by microwave plasma CVD system.
- In the Results and Discussion section, the sentence on page 3, line 129:
„The three samples deposited under the same growth conditions. Figure 2(a) shows that the thermal signal of the periodic structure SiNx sample changes faster with time, implying faster heat transfer.”
should be improved in a following way:
The three samples were deposited under the same growth conditions. Figure 2(a) shows that the thermal signal of the periodic structure of SiNx sample changes faster with time, implying faster heat transfer.
- In the Results and Discussion section, the sentence on page 4, line 139:
„A more detailed analysis of sensitivity is reflected in a previous report Jia Xin9.”
should be improved in a following way:
A more detailed analysis of sensitivity is reflected in a previous report of Jia Xin9.
- In the Results and Discussion section, the sentence on page 4, line 143:
„In addition, the required the value of RAl/dia (TBRAl/dia) and RGaN/Si (TBRGaN/Si) can be found in Ref9.”
should be improved in a following way:
In addition, the required value of RAl/dia (TBRAl/dia) and RGaN/Si (TBRGaN/Si) can be found in Ref9.”
- In the Results and Discussion section, the sentence on page 4, line 153:
„Preious21 reported showed that reducing the TBR of the GaN-on-Diamond form 50±5m2KGW−1 to 12m2KGW−1 by reducing the thickness of the SiNx layer and the diamond nucleation layer.”
should be improved in a following way:
Previous21 report showed that reducing the TBR of the GaN-on-Diamond from 50±5m2KGW−1 to 12m2KGW−1 can be obtained by reducing the thickness of the SiNx layer and the diamond nucleation layer.
- In the Results and Discussion section, the sentence on page 6, line 229:
„…the thickness of the thickness of the diamond film is about 1 μm. But the thickness of the thickness of the diamond film on the surface of the SiN(peri) interlayer is 400nm,…”
should be improved in a following way:
„…the thickness of the diamond film is about 1 μm. But the thickness of the diamond film on the surface of the SiN(peri) interlayer is 400nm,…”
- In the Results and Discussion section, the sentence on page 6, line 233:
„Therefore, a thinner low qualit diamond layer can reduce the thermal boundary resistance of the GaN/diamond.”
should be improved in a following way:
Therefore, a thinner low quality diamond layer can reduce the thermal boundary resistance of the GaN/diamond.
- In the Conclusions section, the sentence on page 7, lines 241-242:
„In summary, this work reports the SiNx(orig) and SiNx(peri) are used as the interlayers to growing diamond on the GaN surface, respectively. The TBReff, Dia/GaN of both structures are incestigated by using the time-domain thermoreflectance technique.”
should be improved in a following way:
In summary, this work reports on the SiNx(orig) and SiNx(peri) that are used as the interlayers to grow diamond on the GaN surface. The TBReff, Dia/GaN of both structures are investigated by using the time-domain thermoreflectance technique.
2. The authors should change the order of the references cited in the manuscript. In the Introduction section, in the sentence on page 1, line 34, the ref. 6-8 are cited. After them, in the sentence on the same page, line 37, ref. 10-13 are cited. There is lack of ref. 9. This reference is cited on page 3, in line 121. The authors should keep the order of cited references.
3. To the units of the thermal conductivity. The authors use two notations of units of thermal conductivity: W/(mK) or W/m·K. They should decide on one form.
4. The symbol of the first sample in Table 2 is different in comparison to the symbol of the same sample in Fig. 2a. I guess that in Table 2 it should be written SiNx(Orig) instead of SiNx(org).
5. The Conclusions section is too short. It should be supported by the results.
Author Response
Dear Reviewer,
Firstly, we would like to show our sincere thanks and respect for your comments and suggestions on our manuscript. All the information you described in the review letter is very useful and valuable to us.
Response to your comments and suggested revisions are listed and answered one by one as follows:
Dear Authors, I have carefully read your paper entitled "The effect of interlayer microstructure on the thermal boundary resistance of GaN/diamond substrate". I believe the article is acceptable for publication after rewriting the manuscript according to the questions or proposals posed below:
Response: Dear reviewer, thank you very much for your comments and very helpful suggestions. I think this manuscript now is improved significantly after revision as your suggestions. The response for each comment is shown as following.
Comment-1：Some correction of English language is required:
- In the Abstract section, the sentence on page 1, line 14:
„Combination with time-domain thermoreflectance measurement and microstructural analysis, the TBReff, Dia/GaN is dominated by the microstructure of the SiNx interlayer, which effect the diamond growth seeding and the diamond nucleation surface.”
should be improved in a following way:
Combination with time-domain thermoreflectance measurement and microstructural analysis, the TBReff, Dia/GaN is dominated by the microstructure of the SiNx interlayer, which effects the diamond growth seeding and the diamond nucleation surface.
- In the Introduction section, the sentence on page 1, line 26:
„With increasing power density and decreasing size of GaN-based electronic power devices that the heat dissipation has become a key problem for practical applications.”
should be improved in a following way:
With increasing power density and decreasing size of GaN-based electronic power devices, heat dissipation has become a key problem for practical applications.
- In the Introduction section, the sentence on page 1, line 39:
„The important parameters of the devices are hinghly dependent on the thermal management technology of the device, such as gain, saturated power and maximum frequency.”
should be improved in a following way:
The important parameters of the devices are highly dependent on the thermal management technology of the device, such as gain, saturated power and maximum frequency.
- In the Introduction section, the sentence on page 2, line 72:
„Therefore, the SiNx film is introduced as the interlayer to relieve the problems of thermal expamsion coefficients and lattic mismatch between on the GaN and diamond.”
should be improved in a following way:
Therefore, the SiNx film is introduced as the interlayer to relieve the problems of thermal expansion coefficients and lattice mismatch between the GaN and diamond.
- In the Introduction section, the sentence on page 2, line 91:
„The purpose of this study is to better understand interfacial layers and structure design of SiNx interlayer play a significant role in enhancing thermal transport in GaN-on-diamond devices through decreasing TBReff, Dia/GaN of the interface.”
should be improved in a following way:
The purpose of this study is to better understand the interfacial layers and structure design of the SiNx interlayer, which play a significant role in enhancing thermal transport in GaN-on-diamond devices through decreasing TBReff, Dia/GaN of the interface.
- In the Experimental Details section, the sentence on page 3, line 107:
„Finally, a polycrystalline diamond layer with a thickness of about 2 μm is grown on the surface of GaN/SiNx by microwave plasma CVD systema.”
should be improved in a following way:
Finally, a polycrystalline diamond layer with a thickness of about 2 μm is grown on the surface of GaN/SiNx by microwave plasma CVD system.
- In the Results and Discussion section, the sentence on page 3, line 129:
„The three samples deposited under the same growth conditions. Figure 2(a) shows that the thermal signal of the periodic structure SiNx sample changes faster with time, implying faster heat transfer.”
should be improved in a following way:
The three samples were deposited under the same growth conditions. Figure 2(a) shows that the thermal signal of the periodic structure of SiNx sample changes faster with time, implying faster heat transfer.
- In the Results and Discussion section, the sentence on page 4, line 139:
„A more detailed analysis of sensitivity is reflected in a previous report Jia Xin9.”
should be improved in a following way:
A more detailed analysis of sensitivity is reflected in a previous report of Jia Xin9.
- In the Results and Discussion section, the sentence on page 4, line 143:
„In addition, the required the value of RAl/dia (TBRAl/dia) and RGaN/Si (TBRGaN/Si) can be found in Ref9.”
should be improved in a following way:
In addition, the required value of RAl/dia (TBRAl/dia) and RGaN/Si (TBRGaN/Si) can be found in Ref9.”
- In the Results and Discussion section, the sentence on page 4, line 153:
„Preious21 reported showed that reducing the TBR of the GaN-on-Diamond form 50±5m2KGW−1 to 12m2KGW−1 by reducing the thickness of the SiNx layer and the diamond nucleation layer.”
should be improved in a following way:
Previous21 report showed that reducing the TBR of the GaN-on-Diamond from 50±5m2KGW−1 to 12m2KGW−1 can be obtained by reducing the thickness of the SiNx layer and the diamond nucleation layer.
- In the Results and Discussion section, the sentence on page 6, line 229:
„…the thickness of the thickness of the diamond film is about 1 μm. But the thickness of the thickness of the diamond film on the surface of the SiN(peri) interlayer is 400nm,…”
should be improved in a following way:
„…the thickness of the diamond film is about 1 μm. But the thickness of the diamond film on the surface of the SiN(peri) interlayer is 400nm,…”
- In the Results and Discussion section, the sentence on page 6, line 233:
„Therefore, a thinner low qualit diamond layer can reduce the thermal boundary resistance of the GaN/diamond.”
should be improved in a following way:
Therefore, a thinner low quality diamond layer can reduce the thermal boundary resistance of the GaN/diamond.
- In the Conclusions section, the sentence on page 7, lines 241-242:
„In summary, this work reports the SiNx(orig) and SiNx(peri) are used as the interlayers to growing diamond on the GaN surface, respectively. The TBReff, Dia/GaN of both structures are incestigated by using the time-domain thermoreflectance technique.”
should be improved in a following way:
In summary, this work reports on the SiNx(orig) and SiNx(peri) that are used as the interlayers to grow diamond on the GaN surface. The TBReff, Dia/GaN of both structures are investigated by using the time-domain thermoreflectance technique.
Response: Thank you very much for your detailed comments and suggestions, we have made corresponding changes according to your tips.
Comment-2：The authors should change the order of the references cited in the manuscript. In the Introduction section, in the sentence on page 1, line 34, the ref. 6-8 are cited. After them, in the sentence on the same page, line 37, ref. 10-13 are cited. There is lack of ref. 9. This reference is cited on page 3, in line 121. The authors should keep the order of cited references.
Response: Thank you very much for your comments, we have changed the order of the references cited in the manuscript.
Comment-3：To the units of the thermal conductivity. The authors use two notations of units of thermal conductivity: W/(mK) or W/m·K. They should decide on one form.
Response: Thank you very much for the comments, the units of the thermal conductivity have been unified.
Comment-4：The symbol of the first sample in Table 2 is different in comparison to the symbol of the same sample in Fig. 2a. I guess that in Table 2 it should be written SiNx(Orig) instead of SiNx(org).
Response: Thank you very much for the comments. All SiNx(org) has been replaced by SiNx(orig) in the manuscript.
Comment-5：The Conclusions section is too short. It should be supported by the results.
Response: Dear reviewer, thank you very much for your comments and very helpful suggestions. We have rewritten the conclusion section. We believe that the conclusion section has been improved after being revised.
Thank you again for your valuable suggestions and comments. We hope our response to the review is appropriate and correct.
Author Response File: Author Response.docx
Reviewer 3 Report
- The abstract should incorporate a significant outcome or outcomes, as well as a conclusion.
- The authors should formulate the novelty of the work with respect to the other works in the field.
- The authors could address what are the gaps in this work?
- Please discuss further the fact that the method is not entirely successful, identifying the origin of the problem and suggesting further improvements as potential future work.
- Insert the specifics of the instruments used for the experiment and the characterization
- The author needs further explanation of the uniqueness of this work in comparison to the existing works done with the previous reports. The author should discuss their results more by comparing other literature.
- Please discuss further the fact that the method is not entirely successful, identifying the origin of the problem and suggesting further improvements as potential future work.
- The authors should emphasize the contribution of work, future work, technology or knowledge. Also, the drawbacks of this manuscript need to be discussed in the conclusion
- Social implications shall be highlighted in the conclusion
- Please read the paper carefully for English language style, grammar and spelling, and make appropriate corrections and changes.
Author Response
Response Letter
Dear Reviewer,
Firstly, we would like to show our sincere thanks and respect for your comments and suggestions on our manuscript. All the information you described in the review letter is very useful and valuable to us.
Response to your comments and suggested revisions are listed and answered one by one as follows:
Comment-1：The abstract should incorporate a significant outcome or outcomes, as well as a conclusion.
Response: This is a very useful suggestion and corresponding information which has been added in the abstract parts in red fonts.
Comment-2：The authors should formulate the novelty of the work with respect to the other works in the field.
Response: Thank you for your comments and suggestions. We have added an formulate of other works in this field, please find the line 87-95, page 2 in red fonts.
Comment-3：The authors could address what are the gaps in this work?
Response: Dear reviewer, thank you so much for your comment. It is undeniable that the thickness of SiNx in this paper is larger, and the obtained thermal boundary resistance is still large compared to the reports of other researchers. In future work, our research focuses on reducing the SiNx thickness to further reduce the thermal boundary resistance. The gap that can be addressed in this paper is that by optimizing the interface structure, it may be possible to reduce the interface thermal resistance in the further.
Comment-4：Please discuss further the fact that the method is not entirely successful, identifying the origin of the problem and suggesting further improvements as potential future work.
Response: Thank you for your positive comments as well as the valuable suggestions to our study. As mentioned in Response 3, on the one hand, thicker SiNx is chosen as the GaN protective layer in the manuscript. The main reason is that it is difficult to control the etching of GaN in the harsh diamond deposition environment by using a thinner SiNx interlayer, which makes the preparation of GaN/diamond structures failure. On the other hand, the periodic structure of SiNx is partially destroyed after diamond growth in the manuscript, which may lead to some imprecise results. But these will be the direction of our future improvement.
Comment-5：Insert the specifics of the instruments used for the experiment and the characterization.
Response: Thank you for your reminders and suggestions. Details on the use of the instrument have been added to the original manuscript. Please find in the red font in the experiments part.
Comment-6：The author needs further explanation of the uniqueness of this work in comparison to the existing works done with the previous reports. The author should discuss their results more by comparing other literature.
Response: Thank you for your positive comments as well as the valuable suggestions to our study. The uniqueness of this work in comparison with the existing work is that it tries to optimize the interface thermal resistance of diamond/GaN by adjusting the interface structure without reducing the thickness of SiNx, which seems to be useful from the interface thermal resistance results. The periodic structure of SiNx can not only increase the effective heat diffusion area, but also enhance the heat dissipation effect at the nanoscale.
We have added a discussion of other literature, please find in the red font on page 2 line 87-95 and page 5 line 178-186.
Comment-7：Please discuss further the fact that the method is not entirely successful, identifying the origin of the problem and suggesting further improvements as potential future work.
Response：Thank you for your positive comments as well as the valuable suggestions to our study. This comment seems to be the same as comment-4, please refer to response 4.
Comment-8：The authors should emphasize the contribution of work, future work, technology or knowledge. Also, the drawbacks of this manuscript need to be discussed in the conclusion.
Response: Thank you very much for your comments and suggestions. We have added a corresponding discussion to the conclusion section in the original manuscript. We hope this modification is appropriate.
Comment-9：Social implications shall be highlighted in the conclusion.
Response: Thank you very much for your comments and suggestions. The social implications has been added in the conclusion, this can be found in the revised manuscript.
Comment-10：Please read the paper carefully for English language style, grammar and spelling, and make appropriate corrections and changes.
Response: Thank you very much for your comments and suggestions. We have carefully corrected and revised the English language style, grammar and spelling in the manuscript. For example, "Prei vs. Peri.", "incestigated", "adsorption", "With increasing power density and decreasing size of GaN-based electronic power devices, heat dissipation has become a key problem for practical applications". etc.
In the end, we would like to thank you again for your careful and professional reviews of our manuscript. According to your valuable suggestions, the whole manuscript has been revised thoroughly, and more detailed analysis and discussions has been added to further explain our results. Hope the revised manuscript can meet the requirement of publication.
Author Response File: Author Response.docx
Reviewer 4 Report
The paper is devoted for thermal and structural investigations of GaN/SiN/diamond structures. The topic is generally interesting, however the paper contains unexplained places (below) and need major revisions.
Line 86, please add more details about already performed investigations on the SiNx interlayer periodic microstructure on GaN devices properties and add corresponding references.
Please correct all typos, for example line 95 2.. Experimental details, line 245 peridic structure.
Numbers and measurements units should be written separately, for example 7 N, not 7N.
Fig. 1 why for investigations were selected periodic SiNx structures with specific pits size and the step length?
In Fig. 5 EDX investigations can be useful.
Conclusions should be more elaborated.
Author Response
Response Letter
Dear Reviewer,
Firstly, we would like to show our sincere thanks and respect for your comments and suggestions on our manuscript. All the information you described in the review letter is very useful and valuable to us.
Response to your comments and suggested revisions are listed and answered one by one as follows:
The paper is devoted for thermal and structural investigations of GaN/SiN/diamond structures. The topic is generally interesting, however the paper contains unexplained places (below) and need major revisions.
Response: Firstly, we would like to show our sincere thanks and respect for your comments and suggestions on our manuscript. All the information you described in the review letter is very useful and valuable to us.
Response to your comments and suggested revisions are listed and answered one by one as follows:
Comment-1: Line 86, please add more details about already performed investigations on the SiNx interlayer periodic microstructure on GaN devices properties and add corresponding references.
Response: The SiNx periodic structure is obtained by inductively coupled plasma etching (ICP) combined with precise mask control method, the process parameters is shown in the table below. Figure 3 shows that SiNx is not a periodic structure due to the etching of SiNx by hydrogen plasma during the diamond deposition process, and its periodicity suffers a certain degree of damage. We have supplemented the etching process in detail, please find the corresponding changes in the revised manuscript with yellow highlights.
Table1 SiNx etching process parameters
|
Material |
ICP/W |
RF/W |
Chamber pressure/Pa |
O2/sccm |
Ar/sccm |
SF6/sccm |
|
SiNx |
100 |
10 |
1 |
5 |
10 |
10 |
Comment-2: Please correct all typos, for example line 95 2.. Experimental details, line 245 peridic structure. We fixed all typos in the manuscript.
Response: Thank you very much for your comments and suggestions.
Comment-3: Numbers and measurements units should be written separately, for example 7 N, not 7N.
Response: Thank you for your positive comments as well as the valuable suggestions to our study. We have revised all similar issues in the manuscript.
Comment-4: Fig. 1 why for investigations were selected periodic SiNx structures with specific pits size and the step length?
Response: Thank you for your positive comments as well as the valuable suggestions to our study. It has been reported in the literature that the average phonon free path of SiNx is less than 20 nm[1]. In addition,the size of the periodic structure of the SiNx interlayer is larger than the average phonon mean free path of SiNx, which will enhance the heat transfer ability theoretically[2]. Therefore, we chose the periodic SiNx structures with a pit size and step size of 20 nm.
- Koji, Watari, Kiyoshi, et al. Effect of Grain Size on the Thermal Conductivity of Si3N4. Journal of the American Ceramic Society, 1999.
- Cahill D G, Ford W K, Goodson K E, et al. Nanoscale thermal transport. Journal of Applied Physics. 2003;93(2):793-818.
Comment-5: In Fig. 5 EDX investigations can be useful.
Response: Thank you very much for your suggestion. We did EDX on the cross-sectional morphology in Figure 5, and the distribution of each element can be seen cleanly. However, due to the relatively primitive model of our EDX instrument, the image quality is not very good, so this result is not added to the manuscript for discussion.
Comment-6:Conclusions should be more elaborated.
Response: Thank you very much for your suggestion, we have revised the conclusion section.
In the end, we would like to thank you again for your careful and professional reviews of our manuscript. According to your valuable suggestions, the whole manuscript has been revised thoroughly, and more detailed analysis and discussions has been added to further explain our results. We hope our response to the review is appropriate and correct.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The manuscript no. coatings-1686141 is after revision and it has been improved. Therefore, it can be accepted for publication in the present form.
Reviewer 3 Report
The revised version of the manuscript is good enough to be published. The authors addressed each comment in detail and made appropriate changes.
Reviewer 4 Report
Authors make proper corrections according to reviewer remarks
and I suggest to publish the paper as it is.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
