LAYER-BY-LAYER GROWTH MODE STABILIZATION AND STEP-EDGE SMOOTHING OF CATION-STABILIZED IN1-XGAXAS STRAINED LAYERS GROWN ON INP

Scanning tunneling microscopy has been used to study the surface morph ology of strained In1-xGaxAs layers (either 2% compressively or 2% ten silely strained for x=0.18 or x=0.75, respectively) grown by molecular beam epitaxy on (001) InP substrate under cation-stabilized condition s. Under such growing conditions a smooth two-dimensional (2D) surface morphology is well preserved until the onset of plastic relaxation. T his behavior is completely unlike the 2D/3D growth mode transition obs erved under As-stabilized conditions of growth. Along with the 2D grow th mode stabilization, a step-edge smoothing is also observed. These r esults are assigned to a high value of step formation free energy on ( 4x2) reconstructed surfaces. The resultant increase in surface tension delays the onset of coherent 3D island formation beyond the onset of plastic relaxation and stabilizes 2D growth. (C) 1998 American Vacuum Society.