GROWTH-RATE SELF-LIMITATION MECHANISM IN INP ATOMIC LAYER EPITAXY STUDIED BY SURFACE PHOTOABSORPTION

The pyrolysis of trimethylindium (TMI) and phosphine (PH3) on an (001) InP surface is studied by surface photo-absorption. In the same manner as the pyrolysis of trimethylgallium on GaAs, self-limitation is observed in the change in reflectivity when TMI is supplied to a P-stabilized surface at 350-degrees-C. This result indicates that the surface is saturated by TMI adsorption to form a CH3-terminated In surface. H-2 purging after TMI adsorption increases the reflectivity further to the level of a metal surface with an In monolayer, indicating that CH3 groups desorb during purging. This paper also finds the pyrolysis of PH3 on a CH3-terminated In surface is much slower than on In metal surface. The growth rate is self-limited to less than one monolayer per cycle in InP atomic layer epitaxy because the surface is not completely transformed to a P surface during PH3 supply, as PH3 pyrolysis is slow on a CH3-terminated In surface. The growth rate approaches one monolayer per cycle when PH3 is supplied to an In metal surface produced by CH3 desorption.