Electrochemical Capacitance Voltage Profiling of the Narrow Band Gap Semiconductor InAs

The design of compound semiconductor based devices increasingly requires the integration of materials of differing band gaps. This is achieved by depositing layers of different semiconductors epitaxially on a substrate. Techniques such as molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) can be used to precisely control the thickness and chemical composition of heteroepitaxial layers, as well as to introduce dopant species in-situ. The electrical properties of some heterostructure systems, such as GaAs/AlGaAs, have been studied extensively, but those of materials such as InAs are not well known. InAs is a narrow band gap semiconductor whose potential applications include infra-red detectors, high speed transistors and magnetic field sensing devices. Lattice mismatches of 7% and 11%, respectively, with GaAs and GaP result in high threading dislocation densities, which are spatially inhomogeneous, when InAs is grown on these substrates.1,2 This is seen in Fig. 1 for an InAs/GaP heterostructure. The decrease in dislocation density with distance away from the heterointerface leads to a corresponding drop in carrier concentration in nominally undoped material.2 The lattice defects also inElectrochemical Capacitance Voltage Profiling of the Narrow Band Gap Semiconductor InAs