Undoped GaSb Grown on the Structure of In0.3Ga0.7As/GaAs Strain Layer Superlattice by MOCVD

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Abstract
Undoped GaSb epilayers have been grown on In0.3Ga0.7As/GaAs strain layer superlattice (SLS) by low pressure MOCVD. The SLS was used to reduce the large lattice mismatch (7%) between GaSb and GaAs. The epitaxial properties were examined by X-ray diffraction and Hall measurement. The X-ray diffraction peaks deteriorated when growth temperature exceeded 600°C. The hole concentration increased and the mobility decreased with increasing growth temperature. The better growth temperature is at the low end of the range between 550 and 635°C. This result is similar to that obtained from X-ray diffraction. The lowest 77 K concentration was 1.5×1016 cm-3 and the highest 77 K mobility was 1800 cm2/V·s. From the TEM photographs of GaSb/SLS/GaAs samples, it is observed that the dislocations have bent before reaching the epilayer surface, while the dislocations propagated up to the surface in GaSb/GaAs samples. From the comparisons of the electrical properties between GaSb epilayers grown on SLS/GaAs substrates and those grown directly on (100) GaAs substrates, it is found that the former have superior electrical properties.