ATOMIC-FORCE MICROSCOPY STUDY OF ZNSE GAAS HETEROEPITAXY PROCESSES BYMETALORGANIC VAPOR-PHASE EPITAXY/

We investigate the initial growth of ZnSe on (001) GaAs in metalorgani c vapour phase epitaxy using atomic force microscopy, X-ray diffractio n, and photoluminescence, GaAs surfaces become atomically fiat after t hermal cleaning at a temperature of 620-750 degrees C. The property of ZnSe films is critically dependent on the GaAs surface preparation an d the flow rate ratio of Se to Zn. The simultaneous As flow during the rmal cleaning is effective to prow high-quality ZnSe films. The growth processes at the initial stages of heteroepitaxy of ZnSe on GaAs are dominated by the two-dimensional growth mode for Zn-rich growth condit ions, while those are dominated by the three-dimensional growth mode a s the Se flow, rate increased. The optimum condition for the ZnSe opti cal quality is different from that for the initial two-dimensional gro wth. grow atomically flat ZnSe films with better optical quality. We d emonstrate that the 2-step growth is effective to grow atomically flat ZnSe films with better optical quality.