TRANSPORT-PROPERTIES OF INAS EPILAYERS GROWN BY MOLECULAR-BEAM EPITAXY

Hall effect and electrical resistivity measurements were carried out on InAs epilayers grown by molecular beam epitaxy (MBE) from a dimeric As 2 source. As evidenced from the measurements, the electrical transport coefficients depend on the epilayer thickness, flux ratio and substrate temperature. In particular, a strained-layer superlattice (SLS) as the InAs/substrate interface was found to be important in reducing the defect density. For layers grown at optimum conditions, the carrier density decreases with thickness d while the Hall mobility reaches a certain saturation ( approximately 5*104 cm2 V-1 s -1) for d>3.0 mu m. The mobility peaks at around liquid nitrogen temperature for thick samples and at higher temperatures for thin layers, which the author explains in terms of impurity scattering. In addition to ionised impurity and optical phonon scattering, possible mechanisms limiting mobility are discussed in these compensated layers. No carrier freeze-out was observed; instead, an apparent increase in carrier density due to impurity conduction was found.