Structural Analysis of Highly Relaxed GaSb Grown on GaAs Substrates with Periodic Interfacial Array of 90° Misfit Dislocations

A Jallipalli,K Nunna,G Balakrishnan,Sh Huang,Tj Rotter,Bl Liang,Lr Dawson,Dl Huffaker

doi:10.1007/s11671-009-9420-9

Abstract

We report structural analysis of completely relaxed GaSb epitaxial layers deposited monolithically on GaAs substrates using interfacial misfit (IMF) array growth mode. Unlike the traditional tetragonal distortion approach, strain due to the lattice mismatch is spontaneously relieved at the heterointerface in this growth. The complete and instantaneous strain relief at the GaSb/GaAs interface is achieved by the formation of a two-dimensional Lomer dislocation network comprising of pure-edge (90°) dislocations along both [110] and [1-10]. In the present analysis, structural properties of GaSb deposited using both IMF and non-IMF growths are compared. Moiré fringe patterns along with X-ray diffraction measure the long-range uniformity and strain relaxation of the IMF samples. The proof for the existence of the IMF array and low threading dislocation density is provided with the help of transmission electron micrographs for the GaSb epitaxial layer. Our results indicate that the IMF-grown GaSb is completely (98.5%) relaxed with very low density of threading dislocations (105 cm−2), while GaSb deposited using non-IMF growth is compressively strained and has a higher average density of threading dislocations (>109 cm−2).

Highlights

Antimonide semiconductors have potential application in a wide range of electronic and opto-electronic devices due to their unique band-structure alignments, and small effective mass as well as high mobility for electrons [1,2,3,4]
The dislocation network associated with the interfacial misfit (IMF) array formation along both [110] and [1,2,3,4,5,6,7,8,9,10] is characterized as a 2D Lomer dislocation network
High quality ‘‘buffer-free’’ GaSb is grown on GaAs substrates with very low threading dislocations (TDs) densities (*105 cm-2) despite the high (7.8%) lattice mismatch

Summary

Introduction

Antimonide semiconductors have potential application in a wide range of electronic and opto-electronic devices due to their unique band-structure alignments, and small effective mass as well as high mobility for electrons [1,2,3,4]. While recent technical advancements have enabled high quality lattice matched GaSb epitaxy on native substrates, for many applications GaAs substrates are desirable. This is because of the following reasons: GaAs is inexpensive, has favorable thermal properties, transparent to more (long wave length) active regions, forms excellent n and p ohmic contacts, and can be semi-insulating compared to GaSb. the high (7.8%) lattice mismatch between the GaSb epilayer and the GaAs substrate complicates the growth of sophisticated device structures. While this approach has enabled a number of device demonstrations [7], it exhibits several deficiencies such as the necessity to grow thick buffer layers (often [1 lm), poor thermal and Nanoscale Res Lett (2009) 4:1458–1462 electrical conductivity, and has resulted in significant material degradation through the presence of threading dislocations (TDs)

Methods

Results

Conclusion