Interfacet migration and defect formation in heteroepitaxy on patterned substrates: AlGaAs and InGaAs on GaAs (100) in MBE

Abstract

We present results for lattice matched (AlxGai..xAs, x=0.5 and x=0.0) and lattice mismatched (InxGai..xAs, x□0.25) growth on patterned GaAs (100) substrates. For the AlGai..xAs structures, the GaAs substrates were patterned in the form of elongated mesas parallel to [011 II with widths of approximately 3 tim. Interfacet migration effects observed on the nesas via cross-section transmission electron microscope studies are explained in terms of a ledge-ledge interaction on the vicinal surfaces formed due to growth on the mesas. InxGai..xAs (x□0.25) structures were grown on GaAs (100) substrates patterned in the form of elongated mesas parallel to [01 11 with widths of approximately 1 tim. This patterning direction was chosen since under cutting in the [0 1 1] direction eliminates inter-facet migration effects so that compositional change induced strain effects can be minimised. For x □0.15, we find a reduction in misfit dislocation densities in films upto five times the nominal critical thickness for growths on the patterned mesas as compared to the growths on the corresponding non patterned regions. For x=0.25 no such difference is observed and a large number ofthreading dislocations ( around iO cm2) are found in both the patterned and the non patterned regions. This is believed to be a consequence of the onset ofa 3-D island growth mode. Finally we present some results for the growth of InO5Gaj75As I AlAs resonant tunneling diode (RTD) structures and a 100 period InjUGaU8As (80 A) IGaAs (160 A) Multiple Quantum Well (MQW) such as suited for spatial light modulator (SLM) structures on GaAs (100) substrates patterned in both directions on a length scale of 12 to 20 tm. For the RTD structures we conclude that benefits from patterning are expected for x□0.25 provided the growth kinetics are appropriately adjusted to prevent 3D island growth mode. For the MQW -SLMstructure we demonstrate superior optical properties for the growth in the patterned region and a corresponding absence of threading dislocations in the central region of the mesas.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.