EPITAXIAL LAYER MORPHOLOGY OF HIGHLY STRAINED GAINAS INP MULTIPLE-QUANTUM-WELL STRUCTURES GROWN BY CBE/

We present a study of changes in the layer morphology of tensilely str ained GaInAs/InP multiple quantum well (MQW) structures in dependence on strain and substrate off-orientation. Growth was performed by chemi cal beam epitaxy (CBE). For high tensile strain (x(Ga) = 0.77) lateral thickness fluctuations evolving into facets of the (411)A type are ob served in cross-sectional transmission electron microscopy (TEM). Thes e undulations are parallel to [01 (1) over bar] and present for sample s grown on both exactly oriented and off-oriented (100) InP substrates . For off-oriented substrates the strain induced generation of macrost eps parallel to the surface steps is detected for x(Ga) = 0.65 and x(G a) = 0.77. The distance and height of the macrosteps directly correspo nd to the substrate off-orientation angle. While the macrostep generat ion is a direct consequence of surface steps in combination with strai n, the occurrence of the undulations might be connected with the (2 x 4) surface reconstruction during CBE growth. Both mechanisms are discu ssed with respect to experimental and theoretical literature data. (C) 1997 Elsevier Science Ltd.