Analysis of the growth modes for gallium arsenide metalorganic vapor-phaseepitaxy

The surface roughness of gallium arsenide (001) films produced by metalorga nic vapor-phase epitaxy has been studied as a function of temperature and g rowth rate by in situ scanning tunneling microscopy. Height-height correlat ion analysis reveals that the root-mean-height difference follows a power-l aw dependence on lateral separation, i.e., Gamma(L)=kL(a), up to a critical distance L-c, after which it remains constant. For layer-by-layer growth, the roughness exponent, alpha, equals 0.25+/-0.05, whereas the critical dis tance increases from 50 to 150 nm as the substrate temperature increases fr om 825 to 900 K. The roughness exponent jumps to 0.65+/-0.1 upon transition ing to three-dimensional island growth. By relating the height-height corre lation analysis to the Einstein diffusivity relationship, the activation en ergy for gallium surface diffusion has been estimated: E-d=1.35+/-0.1 eV. ( C) 2000 American Institute of Physics. [S0021-8979(00)01013-6].