^{1,a)}, Stacia Keller

^{1}, Thomas E. Mates

^{2}, James S. Speck

^{2}, Steven P. DenBaars

^{1,2}and Umesh K. Mishra

^{1}

### Abstract

layers, with , were grown on GaN on both the In-polar and N-polar orientations by metal organic chemical vapor deposition. The impact of growth conditions, including temperature and the group-III flow rates, on the surface morphology and indium mole fraction was investigated. In-polar layers had a smooth surface morphology characterized by mounds which decreased in size with increasing supersaturation during growth. Smooth N-polar InAlN was achieved through the use of vicinal sapphire substrates with misorientation angles of 3°–5° toward , and a trend of an increase in step bunching with decreasing supersaturation was observed for N-polar InAlN layers. The indium incorporation increased with decreasing growth temperature and increasing growth rate for both In-polar and N-polar layers. The indium incorporation was similar for both orientations on samples which were coloaded in our reactor.

The authors gratefully acknowledge the support of the ONR and Dr. Paul Maki.

I. INTRODUCTION

II. EXPERIMENT

III. RESULTS AND DISCUSSION

A. Determination of atomic composition by XRD and XPS

B. Indium composition

C. Surface morphology

1. In-polar InAlN

2. N-polar InAlN

IV. DISCUSSION

V. CONCLUSIONS

### Key Topics

- Surface morphology
- 18.0
- Atomic force microscopy
- 11.0
- Indium
- 11.0
- III-V semiconductors
- 10.0
- Metal organic chemical vapor deposition
- 9.0

## Figures

XPS spectra of 25-nm-thick (a) In-polar and (b) N-polar InAlN layers. The atomic compositions were 0.177 and 0.153 for In polar and N polar, respectively, and the Ga composition was less than 1% for both samples.

XPS spectra of 25-nm-thick (a) In-polar and (b) N-polar InAlN layers. The atomic compositions were 0.177 and 0.153 for In polar and N polar, respectively, and the Ga composition was less than 1% for both samples.

Indium mole fraction plotted as a function of TMIn flow rate for both In-polar (black squares) and N-polar (red circles) InAlN layers.

Indium mole fraction plotted as a function of TMIn flow rate for both In-polar (black squares) and N-polar (red circles) InAlN layers.

Indium mole fraction plotted vs growth temperature for (a) In-polar and (b) N-polar InAlN.

Indium mole fraction plotted vs growth temperature for (a) In-polar and (b) N-polar InAlN.

Indium mole fraction plotted vs TMAl flow rate for both (a) In-polar and (b) N-polar InAlN.

Indium mole fraction plotted vs TMAl flow rate for both (a) In-polar and (b) N-polar InAlN.

Indium mole fraction of N-polar InAlN plotted vs substrate misorientation angle toward the -plane.

Indium mole fraction of N-polar InAlN plotted vs substrate misorientation angle toward the -plane.

AFM images of In-polar InAlN layers grown using temperatures of (a) , (b) , and (c) . The height scale is 5 nm.

AFM images of In-polar InAlN layers grown using temperatures of (a) , (b) , and (c) . The height scale is 5 nm.

AFM images of In-polar InAlN layers grown using TMAl flow rates of (a) , (b) , (c) , and (d) . The height scale for these images is 5 nm.

AFM images of In-polar InAlN layers grown using TMAl flow rates of (a) , (b) , (c) , and (d) . The height scale for these images is 5 nm.

AFM image of In-polar InAlN grown with a TMAl flow rate of plotted with a height scale of 5 nm. Spiral hillocks centered on screw dislocations are clearly visible.

AFM image of In-polar InAlN grown with a TMAl flow rate of plotted with a height scale of 5 nm. Spiral hillocks centered on screw dislocations are clearly visible.

AFM images of In-polar InAlN layers grown using TMIn flow rates of (a) , (b) , and (c) . The height scale is 5 nm.

AFM images of In-polar InAlN layers grown using TMIn flow rates of (a) , (b) , and (c) . The height scale is 5 nm.

AFM image of a -thick N-polar GaN layer grown on a vicinal sapphire substrate with a misorientation of 4° toward the -plane. This represents a typical surface morphology upon which our N-polar InAlN layers were grown. The height scale is 10 nm.

AFM image of a -thick N-polar GaN layer grown on a vicinal sapphire substrate with a misorientation of 4° toward the -plane. This represents a typical surface morphology upon which our N-polar InAlN layers were grown. The height scale is 10 nm.

AFM images of N-polar InAlN layers grown at temperatures of (a) , (b) , and (c) . The height scale is 10 nm.

AFM images of N-polar InAlN layers grown at temperatures of (a) , (b) , and (c) . The height scale is 10 nm.

AFM images of In-polar InAlN layers grown using TMAl flow rates of (a) , (b) , and (c) . The height scale for these images is 10 nm.

AFM images of In-polar InAlN layers grown using TMAl flow rates of (a) , (b) , and (c) . The height scale for these images is 10 nm.

AFM images of N-polar InAlN layers grown using TMIn flow rates of (a) , (b) , and (c) . The height scale is 10 nm.

AFM images of N-polar InAlN layers grown using TMIn flow rates of (a) , (b) , and (c) . The height scale is 10 nm.

AFM images of N-polar InAlN layers grown with substrate misorientations of (a) 2°, (b) 3°, (c) 4°, and (d) 5° toward the -sapphire plane (-plane of GaN). The rms roughnesses for these images are (a) 1.83 nm, (b) 2.03 nm, (c) 1.05 nm, and (d) 1.14 nm. The height scale for these images is 10 nm.

AFM images of N-polar InAlN layers grown with substrate misorientations of (a) 2°, (b) 3°, (c) 4°, and (d) 5° toward the -sapphire plane (-plane of GaN). The rms roughnesses for these images are (a) 1.83 nm, (b) 2.03 nm, (c) 1.05 nm, and (d) 1.14 nm. The height scale for these images is 10 nm.

## Tables

Summary of growth conditions and results for the In-polar InAlN layers investigated in this study.

Summary of growth conditions and results for the In-polar InAlN layers investigated in this study.

Summary of growth conditions and results for N-polar InAlN layers. Note that NC and NI represent the same sample listed twice for clarity.

Summary of growth conditions and results for N-polar InAlN layers. Note that NC and NI represent the same sample listed twice for clarity.

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