EVIDENCE OF 2-SPECIES NUCLEATION OF INAS ISLANDS ON (100)GAAS AND (111)B-GAAS SUBSTRATES

The nucleation of InAs islands on (100) and (111)B GaAs substrates dur ing metalorganic chemical vapor deposition has been investigated via s canning electron microscopy. The measured values of island density are 4-5 orders of magnitude smaller than those predicted using convention al one-species nucleation theory. In addition, the effect of an increa se in arsine flow on island density is opposite in sense for the two s ubstrate orientations. To explain these observations, we further devel op a two-species picture of nucleation-originally proposed by Stoyanov [Appl. Phys. A50, 349 (1990)]-in which the InAs island density is an explicit function of both the indium flux and the arsenic partial pres sure at the growth interface. This more realistic physical model is in good agreement with the complete set of experimental data. (C) 1996 A merican Institute of Physics.