Effect of electron-beam deposition rate on the electrical properties of Ti/ and Pt/n-GaAs contacts

Abstract

Ti and Pt Schottky contacts were electron-beam evaporated at various rates on n-GaAs and evaluated using conventional I– V measurements. In addition, a numerical method from which the contact resistance of the Schottky metal-GaAs contact can be determined, if the series resistance (determined from I– V measurements), diameter and resistivity of a circular Schottky contact are known, was developed and demonstrated for Ti and Pt Schottky contacts. We have found that the rectifying quality of Pt contacts decreased with decreasing deposition rate, but that the deposition rate had almost no influence on the ideality factors of Ti Schottky contacts. On the other hand, whereas the resistivity of Pt layers was independent of the deposition rate, the resistivity of the Ti contacts increased sharply with decreasing deposition rate. This is explained by Auger electron spectroscopy results which confirmed that the oxygen content in the Ti contacts also increased with decreasing deposition rate. Thus, for a given vacuum environment, a quantitative relationship can be established between the oxygen content of Ti layers and their resistivities on the one hand, and the electron-beam deposition rate on the other hand.