Atomically resolved investigation of InGaAs/InP heterojunction formation during metalorganic vapor-phase epitaxy

We have studied the formation of indium gallium arsenide/indium phosphide heterojunctions during metalorganic vapor-phase epitaxy (MOVPE). The films are characterized using scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and x-ray photoelectron spectroscopy (XPS). Exposing an InP [001] film to 10 mTorr of tertiarybutylarsine below 500/spl deg/C results in the deposition of a thin InAs layer from 1.5 to 5.0 atomic layers thick (2.3 to 7.5 /spl Aring/). The surface of this epilayer remains atomically smooth independent of arsenic exposure time. However, in an overpressure of tertiarybutylarsine at or above 500/spl deg/C, the arsenic atoms diffuse into the bulk, creating strained InAsP films. These films form three-dimensional island structures to relieve the built-up strain.