SELECTIVE GROWTH OF GAAS AND AL0.35GA0.65AS ON GAAS PATTERNED SUBSTRATES BY HCL ASSISTED LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY

The selective epitaxy of GaAs and (Al,Ga)As on a patterned substrate h as been achieved using HCl in the vapour phase. As a first approach, H Cl assisted growth of GaAs and Al0.35Ga0.65As on GaAs free and stripe patterned substrates has been performed. In addition to the expected a nisotropic growth, a strong enhancement of the growth rate was observe d. The relation between electronic quality of grown materials and Cl/( Al + Ga) ratios in the vapour phase studied using low temperature phot oluminescence and Hall effect measurements shows that slight amounts o f HCl in the vapour phase lead to improved GaAs and (Al,Ga)As layers. The solid composition of (Al,Ga)As alloys presents a strong dependence upon Cl/(AI + Ga) ratios, correlated to the competition between alumi nium and gallium chlorides formation in the vapour phase. A thermodyna mic analysis of the vapour phase, assuming equilibrium conditions is p resented.