METAL-ORGANIC VAPOR-PHASE EPITAXIAL-GROWTH OF SYMMETRICALLY STRAINED (GAIN)AS/GA(PAS) SUPERLATTICES

Novel symmetrically strained (GaIn)As/Ga(PAs) superlattices (symm. SLS) are realized by metal-organic vapour-phase epitaxy (MOVPE). The structural and optical properties of the symm. SLS are determined by means of high-resolution X-ray diffraction (XRD) as well as by photoluminescence (PL) and excitation spectroscopy (PLE) and are compared also to one-side strained (GaIn)As/GaAs as well as Ga(PAs)/GaAs SLS. The optimization of growth conditions with respect to substrate misorientation and growth temperature is presented and discussed. In order to realize high-quality symm. SLS, it is important to avoid growth surface irregularities, i.e. steps introduced by substrate misorientation, or rough surface morphologies, leading to an enhanced strain relaxation. The residual average lattice mismatch is below 5 x 10(-4) for 50 period SLS layers, having lattice mismatches of up to +/- 2.4 x 10(-2) in the individual layers. Because of this almost perfect symmetric strain profile, the SL critical thickness becomes much larger than the typical layer thickness. Narrow XRD linewidths for the superlattice satellite peaks of 20'' to 30'' (FWHM) are obtained. First PL and PLE studies are briefly described and discussed with respect to the exciton binding energy in this system, providing indication of a considerably reduced in-plane hole mass in these symm. SLS.