Background and interface electron populations in InAs_0.58Sb_0.42

The unintentional background electron population and associated interface and surface conductivity in a heterostructure of InAs_0.58Sb_0.42 with a bandgap of 0.144 eV and AlInSb was studied with multi-carrier Hall-effect analysis. A free electron bulk concentration at 77 K was found with a density of 2.4×10¹⁵ cm^-3and mobility of 140 000 cm² V^-1 s^-1. A surface electron accumulation layer was observed with a density of 5.5×10¹¹ cm^-2 and mobility of 4500 cm² V^-1 s^-1 that is consistent with predictions of surface Fermi level pinning. Another accumulation layer was identified at the interface with the AlInSb of 4×10¹¹ cm^-2 with a mobility of 37 000 cm² V^-1 s^-1. The origin of the defects and the implications for device structures are discussed.