Schottky barrier induced injecting contact on wide band gap semiconductors

Abstract

A new method is proposed by which a minority carrier injecting contact or ohmic contact can be attained in wide band gap II–VI semiconductors. The basic principle is to use a forming process, i.e., an applied electric field at an elevated temperature in the Schottky contact, to spatially separate dopants from compensating centers. In this way, the ratio of dopants to compensating centers can be greatly increased at the semiconductor surface. Upon cooling, the dopant concentrations are frozen to retain a large net concentration of dopants in a thin surface layer, resulting in a depletion layer that is sufficiently thin to allow tunneling injection. Calculations of band profiles, distributions of doping concentrations, and current–voltage characteristics are performed on Al doped ZnTe, in which Al donors complex with doubly negatively ionized Zn vacancies to produce total compensation. The results indicate that the doping concentration and the total band bending during the forming process are the crucial factors for achieving injecting contacts. For Schottky barrier heights above 1 eV, doping concentrations as high as 10^20 cm^–3 are needed.