UNDOPED GASB GROWN ON THE STRUCTURE OF IN0.3GA0.7AS/GAAS STRAIN LAYER SUPERLATTICE BY MOCVD

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-degrees-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-degrees-C. This result is similar to that obtained from X-ray diffraction. The lowest 77 K concentration was 1.5 x 10(16) 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.