MOLECULAR-BEAM EPITAXY GROWTH AND CHARACTERIZATION OF THIN (LESS-THAN-2-MU-M) GASB LAYERS ON GAAS(100) SUBSTRATES

This paper reports the effect of growth parameters and buffer structure on the luminescence, electrical and structural characteristics of thin (< 2 mum) GaSb layers grown by molecular beam epitaxy (MBE) on GaAs(100) substrates. A two-stage substrate temperature growth regime has been developed on the basis of a thermodynamic consideration of the growth process, taking into account the additional Gibbs free energy due to the strain at the initial growth. This regime permits the growth of GaSb epilayers with a small Sb/Ga ratio at high substrate temperatures; it provides a greater exciton photoluminescence (PL) intensity and Hall mobility (over 5000 cm2 V-1 s-1 at 77 K) and improves the layer quality. The appearance of a free exciton luminescence line (809 meV) in the PL spectra of MBE GaSb/GaAs is reported for the first time. It is also shown that a (50 angstrom AlSb/50 angstrom GaSb)10 short-period superlattice prevents non-radiative recombination centres and carrier scattering centres from propagating in the top GaSb layer but does not bend the misfit dislocation growing through the layer from the GaSb/GaAs interface.