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Published online by Cambridge University Press: 25 February 2011
Undoped GaSb epilayers have been grown on (100) GaSb and S.I. GaAs substrates. The effects of growth temperatures and TMSb/TEGa mole fraction ratios on the epitaxial properties of surface morphology, growth rate, hole concentration and mobility (300K and 77K) have been studied. The lowest concentration 1.8x101 6 cm- 3 (77K) and the highest mdobility 1447 cm2/V.s (77K) can be obtained under V/III ratio of 6.64 at 550°C. Photoluminescence intensity was found to be a function of the V/III ratios. When V/III ratios increased or decreased beyond 6-8, the BE peaks disappeared and PL spectra became roughened.
To reduce the effects of large lattice-mismatch in highly strained GaSb/GaAs system (7% mismatch) on the electrical properties, a 10-period In0.3Ga0.7As/GaAs (60A/40A) strain layer superlattice (SLS) has been grown on GaAs substrates as a dislocation filter before the GaSb epitaxial growth. From the comparison of 77K Hall mobility of GaSb/GaAs as a function of growth temperature with that of GaSb/SLS/GaAs, it was clearly observed that the epilayers grown on SLS structures have higher mobility than those grown directly on GaAs substrates. From the TEM analysis, we observed that all dislocations propagated up to the GaSb epilayer surface in the GaSb/GaAs system but some of the dislocations bending before reaching the epilayer surface in the GaSb/SLS/GaAs system.