DISLOCATION DENSITY REDUCTION IN GASB FILMS GROWN ON GAAS SUBSTRATES BY MOLECULAR-BEAM EPITAXY

The reduction of threading dislocation density due to their mutual int eractions in GaSb thin films grown on (001) GaAs substrates by molecul ar beam epitaxy has been investigated. The effectiveness of several bu ffer layer schemes including GaSb/AlSb strained layer superlattice and In0.11Ga0.89Sb/GaAs buffers for threading dislocation suppression was evaluated. High-resolution transmission electron microscopy shows tha t the GaSb/GaAs interface consists of a highly periodic network of 90 degrees pure edge misfit dislocations, with an average spacing close t o that or a fully relaxed system. This results in relatively low threa ding densities in the GaSb epilayer, despite their large lattice const ant mismatch (8.2%). The threading dislocation density as a function o f GaSb film thickness was determined by plan-view transmission electro n microscopy and was found to decrease with film thickness due to mutu al interactions among dislocations. It was found that a strained layer superlattice of GaSb/AlSb, with each layer close to its critical thic kness, is the most effective in threading density reduction.