Molecular-beam epitaxial growth and transport properties of InAs epilayers

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Abstract
InAs epilayers have been grown on (100)-GaAs substrates by molecular-beam epitaxy using an As2 source, and their properties were investigated by the Hall effect and resistivity measurements. The transport properties were found to be critically dependent on the epilayer thickness d>3.0 μm, flux ratio of constituents, and substrate temperature. Particularly, a strained layer superlattice at the InAs/substrate interface was found important in reducing defect density. For the layers grown at optimum conditions, the Hall mobility reaches a certain saturation for about d>3.0 μm. The mobility peaks at around liquid-nitrogen temperature for thick samples and at higher temperatures for thin as well as etched layers, which we explain in terms of impurity scattering of carriers. In addition to ionized impurity and optical phonon scattering, other possible mechanisms limiting mobility are discussed in these compensated layers. No carrier freezeout was observed at temperatures down to 10 K. Instead, an apparent increase in carrier density due to impurity conduction was found. The existence of three spatial regions contributing to the conduction was confirmed from etching experiments. The results were compared with those of the InAs epilayers grown under similar conditions on Si substrates.