IMPROVEMENT IN THE ELECTRICAL-PROPERTIES OF GAAS INAS/GAAS STRUCTURESTHROUGH THE USE OF (111)A SUBSTRATES/

We compare the electrical properties of InAs thin films embedded in Ga As layers grown by solid source molecular beam epitaxy on (111)A and ( 001) substrates. A major improvement in Hall mobility through the use of (111)A substrates is confirmed. The carrier concentration is found to saturate at a value of 3 x 10(12) cm(-2) after 50 nm as a function of the InAs thickness. Self-consistent calculation assuming interface Fermi level pinning produces results which are in good agreement with the experimental results, and the pinning position is estimated to be about 0.15 eV above the bottom of the conduction band. The origin of F ermi level pinning seems to be the misfit dislocations confined at the InAs/GaAs interfaces based on structural characterization by transmis sion electron microscopy.