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°C results in the deposition of a thin InAs layer from 1.5 to 5.0 atomic layers thick (2.3 to 7.5 Å). The surface of this epilayer remains atomically smooth independent of arsenic exposure time. However, in an overpressure of tertiarybutylarsine at or above 500°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.