Structural and Optical Properties of InAsSbBi Grown by Molecular Beam Epitaxy on Offcut GaSb Substrates

Round 1

Reviewer 1 Report

In the paper Structural and optical properties of InAsSbBi grown by molecular beam epitaxy on offcut GaSb substrates authors reports their results related with growth and characterization of dilute bismide InAsSbBi material. The paper is well organized and easy to follow. However, at the moment in my opinion is not ready for publication. Authors have to adress some issues listed bellow:

• dilute bismide are very similar to dilute nitride, In my opinion in introduction author should mention about this similarity and highlight the differences between dilute bismide and nitrides
• Fig. 2 - in figure description upper and lower should be relaced with left and right
• line 99 - what is a meaning of  with a #5 mask ?
• XRD analysis - I understand authors conclusions about grown material, however to confirm strain or relaxation of grown InAsSbBi authors should measure a reciprocal sapce maps
• Did authors perform EDX analysis of In-Bi droplets? If yes, does the chemiacal analysis confirms the estimated composition of droplets?
• line 226 - typo error: Nomarksi
• From Fig. 7 we can observe Bi accumulation close to AlSb marker. What is a reason of Bi enrichment at the begining of growth?
• Authors observed  Lateral quasi-periodic composition variation of Bi atoms. What is a most probable origin of such phenomena and why this effect is weak in sample B?

Author Response

Please see attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Additional comments on the work :

1) Reference 4 refers to other works by the authors. Why is this reference cited so often in the article?

2) Authors could insert updated references. 

Author Response

Please see attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Before I start the detailed review of this paper, I will state a couple of my main concerns. One is that this paper is something that I would expect to see in say in Journal of Crystal Growth or similar, rather than in a Photonics journal. The only optical aspect covered is the photoluminescence measurements. Secondly, the authors have already reported on the growth of InAsSbBi in [4]. The growth on these offcut substrates does not seem to do anything for the surface morphology or the optical properties, so it is in that sense a ‘negative’ result. This may still be useful from a fundamental growth point of view for MBE growers but why should I as a device person be interested in this study? I imagine that there was a suspicion that growth on a misoriented substrate may improve the way that the Bi incorporates and hence lead to high Bi% with good structural and optical quality? Some such justification for this study needs to be given I feel.

i) The growth section is very well written but this is not surprising as the group specialize in growth. However, I would like to see a bit more detail. For example, how are the surfaces prepared before the growth? Do the different offcuts require different oxide removal temperatures or techniques? What As species was used for the growth?

ii) Can I check that there is only one period of the 10nm InAs/AlSb partially strain balancing barrier? Why not have more periods?

iii) Is it sensible to use the same 400C for the growth of all the InAsSbBi layers? Should they not have been optimized for each offcut substrate?

iv) The reference InAsSb layer was grown at a higher temperature. What would its PL look like if that was grown at 400C? Would the PL intensity start to be similar to the InAsSbBi layers?

v) Where power dependent PL measurements undertaken on these samples? It would be a very useful addition to this study, showing if the PL was largely radiative or non-radiatively dominated.

vi) The low energy part of the PL spectra shown in Fig.11 all appear to be similar in shape. Can they explain why there is no evidence of any Urbach tail when the Bi is added like we see in reports on GaAsBi?

vii) I would like to see more of a discussion of the integrated PL shown in Fig.13. All the samples including the InAsSb reference show an initial rapid decrease as the temperature increases to about 80K. You can determine an activation energy from this – what is it? From 80K to 300K, the rate of decrease slows down, suggesting a different activation energy is dominating the radiative process. There have been a few studies of the way that the integrated PL changes with temperature in GaAsBi and information about the localized states has been determined. Can the authors have a more detailed discussion of this?

Author Response

Please see attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I really appreciate authors response on my remarks. Now in my opinion paper is ready for publication in Photonics.

Reviewer 3 Report

I'm happy with the changes made by the authors to the manuscript and for explaining some of the points I raised in detail in their response letter. I feel that this is now a more valuable paper and I am happy to recommend its publication.