Tuesday, January 8, 2019

Molecular beam epitaxy growth and characterization of InSb layers on GaAs substrates

The authors have investigated InSb layers grown heteroepitaxially on GaAs(100) substrates by molecular beam epitaxy (MBE). The dependence of electron mobilities on the MBE-growth conditions was investigated. The best room temperature mobility, 55000 cm2 V-1 s-1 for a 2 mu m thick layer, was obtained for a growth temperature of 420 degrees C with an antimony over indium ratio of 1.4. The 14.6% lattice mismatch between epilayer and substrate gives rise to threading dislocations and microtwins, as evidenced by transmission electron microscopy. The defects are shown to reduce the mobility for thin samples. One of the most interesting results of the work is the evidence of an electron accumulation layer at the InSb(100) surface. This result is obtained from temperature-dependent Hall measurements which exhibited two singularities in the carrier concentration versus temperature plot. Calculations of the Hall constant considering parallel conduction is successfully used to model this temperature dependence. The MBE-grown InSb layers are shown to have an unintentional acceptor background. The authors also investigated n-type doping using silicon. It is shown that the measured low temperature carrier concentrations and mobilities in undoped samples are considerably influenced by compensation effects.


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