Absolute determination of the Fermi level pinning at the dielectric/semiconductor interface in GaAs based heterostructures

This paper deals with semiconductor/dielectric interface characterization, and in particular with GaAs/dielectric interface. A new electrical method of investigation, constant Fermi level transient spectroscopy (CFTS), is explained. It is based on MIS-H devices, an acronym that we propose to design gated Hall effect devices incorporating a 2DEG channel in an otherwise depleted heterostructure. The main characteristic of CFTS is that transients are obtained under constant potential conditions in the semiconductor and constant surface potential. This allows a rigorous theoretical analysis of capture/emission process by the interface states. This method is comparable in its spirit to feedback methods such as constant-capacitance DLTS (CC-DLTS). The results obtained prove, firstly, the validity of the CFTS and, secondly, that MIS-H samples can be used both for the determination of Dit and of its energetic position within the bandgap, and thus with a good accuracy and a high level of confidence despite difficulties usually met with GaAs/dielectric interfaces.