Carrier Dynamics in InGaN/GaN on the Basis of Different In Concentrations
Round 1
Reviewer 1 Report
Comments for applsci-481703:
The technology Time-resolved FWM used to characterize the InGaN layer with different composition is indeed interesting but the discussion is too short and I can not get the clear conclusion based on the FWM results author show.
Furthermore, several points like the MOCVD growth of the GaN materials and InGaN layer condition needs to be justified.
A major revision is recommended. Further discussion about the FWM results are expected.
Author Response
The technology Time-resolved FWM used to characterize the InGaN layer with different composition is indeed interesting but the discussion is too short and I cannot get the clear conclusion based on the FWM results author show.
Furthermore, several points like the MOCVD growth of the GaN materials and InGaN layer condition needs to be justified.
A major revision is recommended. Further discussion about the FWM results are expected.
Reply:
The growth conditions of InGaN/GaN samples, we make a detail explanation in the Section 2. We also provide the scheme of InGaN/GaN sample structures used in the Fig. 1. For the FWM results, we had a complete description in the second half of section 3.4. We add a section as the “discussion” before conclusion. The discussion section was shown as following:
From the measurement results of FWM, numerous defects existed in sample PIN27. FWM can only monitor Da and τR values with excitation energy density I0 of 8.8 mJ/cm2. The values of Da and τR reached 2.73 cm2/s and 0.15 ns, respectively. Only one FWM measurement was observed given the remarkably high In doping concentration, whereas a number of high defects were generated in the P-type GaN layer. For sample PIN15, CSI27, and SI27, the values of Da and τR totaled 2.56 cm2/s and 0.45 ns, 1.83 cm2/s and 1.59 ns, and 1.73 cm2/s and 1.48 ns, respectively. Comparison of PIN15 with PIN27 revealed that as In content increased from 15% to 27%, the D value increased from 2.56 cm2/s to 2.73 cm2/s. The grating times of CSI27 and SI27 totaled τG=1.59 ns and τG=1.48 ns, respectively, with no significant difference. Finally, we integrated the XRD, PL, and FWM measurement results, mainly based on the results of FWM measurement of the quality of samples SI27, CSI27, PIN27, and PIN15. According to results, CSI27 showed the best performance, followed by SI27, PIN 27, and finally PIN15.
Reviewer 2 Report
The authors have presented the growth and characterization of different InGaN/GaN-based structures. The manuscript reveals an extensive work, both in terms of growth of alternative structures to improve the optical properties of InGaN layers, and in terms of the several complementary and advanced techniques used to access such properties. Unfortunately, the manuscript presents severe problems of comprehension, the presentation lacking clarity and accuracy. Beside grammar mistakes, often terms are not appropriate and phrases ambiguous. Claims do not appear always motivated, functional or correct. This also applies to citations. The manuscript surely contains a quite large body of experimental work, possibly relevant, but it is presented in a confusing and unfocused manner. I suggest a deep rewriting , neglecting unnecessary details but aiming to communicate clearly the relevant results. In its present form, the manuscript is hardly readable and thus not suitable for publication.
Author Response
The authors have presented the growth and characterization of different InGaN/GaN-based structures. The manuscript reveals an extensive work, both in terms of growth of alternative structures to improve the optical properties of InGaN layers, and in terms of the several complementary and advanced techniques used to access such properties. Unfortunately, the manuscript presents severe problems of comprehension, the presentation lacking clarity and accuracy. Beside grammar mistakes, often terms are not appropriate and phrases ambiguous. Claims do not appear always motivated, functional or correct. This also applies to citations. The manuscript surely contains a quite large body of experimental work, possibly relevant, but it is presented in a confusing and unfocused manner. I suggest a deep rewriting , neglecting unnecessary details but aiming to communicate clearly the relevant results. In its present form, the manuscript is hardly readable and thus not suitable for publication.
Reply:
We make a proofreading by a native English editor.
Reviewer 3 Report
This manuscript reports some interesting results about the optical properties of InGaN/GaN heterostructures.
However, the manuscript is badly organized and poorly written that makes this work not published in its present form. Below, I list, point-by-point, minor and major points that need to be addressed.
Page 1, line 34. What radiosity is?
Page 2, lines 65 and 66. What eta is? I know is the external efficiency, but a quantity must be always defined when it is mentioned for the first time. “In” should ne “InGaN”.
Page 2, lines 85ì4, 85 and 91. What does bond mean? Do the authors mean the chemical bonding?
Page 3, lines 99-101. This sentence has been repeated twice.
Page 3, lines 101 and 126. “Device” should be “set-up”.
Page 4, line 159. A pertinent study regarding high-In concentration InGaN samples is reported by M. De Luca et al., Phys. Rev. B 201202 (2012).
Page 6, line 195. What “liquidation” means? Have the authors performed power-dependent PL on the samples shown in Fig. ? I suggest to display the data in Fig. 4 also on a Log-y-scale to allow the reader to follow the intensity decrease of the PL as well as the evolution of the PL lineshape with temperature.
Page 6, lines 207 and 208. The manner D and tauR should be shown for completeness reasons.
Table 2. The data reported in the Table should be critically discussed highlighting the differences and providing explanations of the observed trends. Make a list of numbers without a critical discussion is useless.
Author Response
This manuscript reports some interesting results about the optical properties of InGaN/GaN heterostructures.
However, the manuscript is badly organized and poorly written that makes this work not published in its present form. Below, I list, point-by-point, minor and major points that need to be addressed.
Page 1, line 34. What radiosity is?
Reply:
The radiosity is “Light energy transfer”.
Page 2, lines 65 and 66. What eta is? I know is the external efficiency, but a quantity must be always defined when it is mentioned for the first time. “In” should ne “InGaN”.
Reply:
We rewrite this sentence as “Okamoto et al. [20] have proven that the great decrease in external quantum efficiency (ηext) of LED in InGaN is not the increase in non-radiative composite centers but the carrier delocalization caused by rapid diffusion.”.
Page 2, lines 85ì4, 85 and 91. What does bond mean? Do the authors mean the chemical bonding?
Reply:
We use the “joining” to replace the “bonding”. We rewrite three sentences as following:
Third, we improved the joining between the In0.27Ga0.73N and GaN layers at 580 °C. CSI27 is a GaN layer with a growth thickness of 120 nm and a growth temperature of 530 °C on SI27. For sample PIN27, the growth steps are as follows. First, we purified the sapphire substrate at 1800 °C, applied nitride to the surface, and grew a thin (1.5 μm) GaN layer at 530 °C. Second, we grew doped Si at 550 °C to form an N-type GaN layer with a thickness of 500 nm. Third, we grew the In0.27Ga0.73N layer at 650 °C. Fourth, we improved the joining between the In0.27Ga0.73N and GaN layers at 580 °C. Fifth, we grew doped Mg at 550 °C to form a P-type GaN layer with a thickness of 120 nm. Sixth, we improved the joining between the In0.27Ga0.73N layer and P-type GaN layers at 580 °C.
Page 3, lines 99-101. This sentence has been repeated twice.
Reply:
We delete the first one sentence in this part.
Page 3, lines 101 and 126. “Device” should be “set-up”.
Reply:
We correct these parts.
Page 4, line 159. A pertinent study regarding high-In concentration InGaN samples is reported by M. De Luca et al., Phys. Rev. B 201202 (2012).
Reply:
We add this sentence in this part.
Page 6, line 195. What “liquidation” means? Have the authors performed power-dependent PL on the samples shown in Fig. ? I suggest to display the data in Fig. 4 also on a Log-y-scale to allow the reader to follow the intensity decrease of the PL as well as the evolution of the PL lineshape with temperature.
Reply:
The “liquidation” means “merge together”. In this study, we do not performed the power-dependent PL measurements due to this measurement cannot provide more information for four-wave mixing. Log-y-scale can make tiny peaks more visible. But in this study, we want discuss the peak position change with temperatures.
Page 6, lines 207 and 208. The manner D and tauR should be shown for completeness reasons.
Reply:
In this part, we had given a detail explanation in the page 4, from line 131 to line 147.
Table 2. The data reported in the Table should be critically discussed highlighting the differences and providing explanations of the observed trends. Make a list of numbers without a critical discussion is useless.
Reply:
In this part, we had given a detail explanation in the second half of section 3.4.
Round 2
Reviewer 1 Report
I recommend this manuscript to be accepted after the minor revision:
Plotting the peak wavelength versus measured temperature (K) to describe carrier dynamics even authors do not observe the "S" shape behavior
Author Response
please see attachment.Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript has been deeply revised and it can be accepted for pubblication
Author Response
We appreciate reviewer’s comment.
Reviewer 3 Report
The authors responded quite satisfactorly to my previous requests
Author Response
We appreciate reviewer’s comment.
