The molecular beam epitaxial growth of InAs on GaAs(111)B- and (100)-oriented substrates: a comparative growth study
Molecular beam epitaxy has been used to simultaneously grow epitaxial InAs onto (111)B- and (100)-oriented GaAs substrates, under a variety of growth conditions. Despite the large lattice mismatch InAs was observed to grow upon GaAs(111)B in a two-dimensional (layer-by-layer) manner, from onset of nucleation to micrometre thicknesses as indicated by clear, well streaked 2*2 reconstructed RHEED patterns throughout the deposition and smooth post-growth scanning tunnelling micrographs. The comparative study of InAs grown upon GaAs(100) followed the expected Stranski-Krastanow growth mode. Systematic variations of the epilayer thickness, substrate temperature and concentration of intentional n-type (Si) dopant, were carried out and the samples measured ex situ by the Hall effect and double-crystal X-ray diffraction. Despite the two-dimensional growth mode, the InAs/GaAs(111)B system was found to be electrically and structurally inferior to the InAs/GaAs(100) system for growth temperatures below 450 degrees C. However, above this temperature the systems became comparable in terms of both the measured electron mobilities and epilayer Bragg peak widths.