Influence of Residual Contamination on the Structure and Properties of Metal/GaAs Interfaces.

摘要

This study shows that interface morphology, orientation relationship, and formation of new phases strongly depend on the surface preparation of GaAs before metal deposition and/or on the annealing environment. The metals investigated (Au, Ag, and Al, with lattice parameters close to each other) deposited in situ on a UHV-cleaved GaAs surface show very similar relationships with GaAs upon annealing. This relationship changes when GaAs is exposed to air before metal deposition. All metals investigated, when deposited on UHV-cleaved GaAs substrate, are stable upon annealing. The interface between metal and GaAs remains abrupt upon annealing. In the case of Cr almost perfect matching to GaAs was observed for UHV deposited samples, but random orientation for air-exposed samples. This study shows that impurities at the semiconductor surface can affect the stability of the barrier height of Schottky contacts. These changes in barrier height depend on the metal used, and on the intensity and direction of the potential and current during the electrical aging. The dramatic example of Ag contacts and their change upon current stressing only for air-exposed samples confirms the importance of surface preparation before metalization. 34 refs., 7 figs., 1 tab.