Effects of oxygen impurities in W films on W/GaAs Schottky-barrier contacts

Abstract

Schottky-barrier characteristics and chemical reactions of contacts between oxygen-contained W films and GaAs substrates annealed up to 800 °C have been investigated. Phase transformation from β-W to α-W of the oxygen-contained W films (3 at. % oxygen), sputter deposited in Ar and O2 gas mixture, is observed at temperatures around 650 °C. Electrical degradation of the contacts, especially in capacitance-voltage (C-V) characteristics, is found after annealing above 650 °C. Oxygen accumulation at the W/GaAs interfacial region and Ga and As atom diffusion into the W films are found by secondary-ion mass spectrometry during annealing. Formation of a Ga2O3 layer at the interfacial region is also detected by x-ray photoemission spectroscopy and transmission electron microscopy. These results suggest that Ga2O3-layer formation is related to the electrical degradation. The C-V characteristics can possibly be explained by series capacitance of an interfacial oxide layer and a depletion layer together with an assumption of nonuniform carrier distribution in the GaAs substrate.

Structure and stability studies on W, WSi, WSiN/GaAs systems by XRD

“…Dependent on the preparation details the coexistence of both phases can be observed often (figure 1(a)). This situation shows some similarity with the results reported by Kuriyama and Ohfuji [2]. The peaks of the β-W family are stress-shifted to smaller 2θ.…”

“…The high-temperature and long-term stability of Schottky contacts on GaAs or related III-V semiconductors have been studied intensely during recent years. The refractory metal tungsten and a variety of W alloys and compounds have been objects of particular study [1][2][3][4][5][6]. These materials are also of importance for the self-aligned refractory gate techniques used for the fabrication of MESFETs and HEMTs.…”