Transport properties of structures containing a-Si : H : Er

Abstract

The I–V characteristics of diode structures containing sputtered a-Si : H : Er films for potential LED applications have been studied. The a-Si : H : Er films were deposited on p⁺ Si substrates. On top of the film, ZnO : Al transparent conductive layers, 3 mm in diameter, were deposited. The back contacts were made of Al. The Er concentration in the films was varied between 0.05 and 0.16 at %, and the hydrogen concentration between 14 and 24 at %. It was found that the log–log plot of the forward I–V characteristic of a typical sample consisted of several regions with different slopes. On the basis of models put forward in the literature, it is proposed that the electron transport in the studied structure is governed by unipolar carrier injection, and the space charge limited currents are controled by two types of electron trap. The first are probably deep acceptor traps formed by dangling bonds, and the second are donor-like levels created by Er–O complexes. The energy positions of these traps are estimated.