Structure of arsenic-treated indium phosphide (001) surfaces during metalorganic vapor-phase epitaxy

We have studied the initial stages of heterojunction formation during the metalorganic vapor-phase epitaxy of indium arsenide on indium phosphide. Exposing an InP (001) film to 10 mTorr of tertiarybutylarsine below 500 degreesC results in the deposition of a thin InAs layer from 1.5 to 5.0 atomic layers thick (2.3-7.5 Angstrom). The surface of this epilayer remains atomically smooth independent of arsenic exposure time. However, in an overpressure of tertiarybutylarsine at or above 500 degreesC, the arsenic atoms diffuse into the bulk, creating strained InAsP films. These films form three-dimensional island structures to relieve the built-up strain. The activation energy and pre-exponential factor for arsenic diffusion into indium phosphide have been determined to be E-d=1.7+/-0.2 eV and D-o=2.3+/-1.0x10(-7) cm(2)/s.