Background and interface electron populations in InAs0.58Sb0.42

The unintentional background electron population and associated interface and surface conductivity in a heterostructure of InAs0.58Sb0.42 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 x 10(15) cm(-3) and mobility of 140 000 cm(2) V(-1)s(-1). A surface electron accumulation layer was observed with a density of 5.5 x 10(11) cm(-2) and mobility of 4500 cm(2)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 x 10(11) cm(-2) with a mobility of 37 000 cm(2) V(-1)s(-1). The origin of the defects and the implications for device structures are discussed.