Admittance spectroscopy study of NiGe contact on GeSn

The direct gap semiconductor germanium tin (GeSn) is an attractive material for next-generation devices in nanoelectronics as well as in photovoltaic applications. However, its detailed electronic properties have not yet been clearly understood. Recently, admittance spectroscopy has become a popular analytical tool in materials research and development because it involves a relatively simple electrical measurement whose results may establish accurate characteristics of materials.

The aim of this work is to study the effects of the annealing temperature on the electrical nature (rectifying or non-rectifying) of the metal contact by admittance spectroscopy. A numerical method, which is based on the solution of the basic semiconductor equations, is applied to simulate the material structure. From the calculation of microscopic quantities such as the modulated carrier concentrations and current densites, we can compute the theoretical admittance and impedance curves as function of frequency and external parameters (temperature and steady-state voltage) and then extract information on the electrical properties of the heterostructure.
By a detailed investigation of the impact of microscopic parameters such as the dopant concentrations and the metal barrier height on the electrical characteristics, our objective is to understand the mechanisms of charge transport between the two electrodes.