Pressure Dependence of the Barrier Height in Tunnel n-GaAs/Au Junctions

Abstract

The theory of tunnel current-voltage (I-V ) characteristics of metal-semiconductor junctions based on the self-consistent solution of Poisson equation allows to get the Schottky-barrier height and the charged impurity concentration directly from the tunneling data. This approach was applied to the analysis of the low temperature experiments on tunneling under pressure up to 3GPa in a piston-cylinder gauge. Here we present the barrier height versus pressure for heavily doped n-GaAs(T e)/Au (Ne ∼ 5 −7 � 10 18 cm −3 ) tunnel junctions and compare the obtained pressure dependence of the Schottky barrier with known behavior of the band gap under pressure taking into account the influence of the L- and X-valleys and DX centers. The knowledge of doping level and the potential barrier height at the interface as well as their dependence on pressure is important for studies of the semiconductor structures where the surface band bending region is essential. Our previous works [1, 2] showed that it is possible to carry out qualitative low-temperature tunneling spectroscopy experiments at pressure up to 3 Gpa using stand-alone high-pressure cell. The aim of this work is to extend this technique to quantitative study of band bending region in heavily-doped semiconductors under high pressure. The pinning of the Fermi level that determines the magnitude of Schottky barrier may be attributed to metal-induced gap states [3]. In the particular case of the Au contact to n-GaAs (100) plane the barrier formation was studied by photoemission spectroscopy on Ne = 5 � 10 18