Processing and reconstruction effects on Al-GaAs(100) barrier heights

We have used low-energy electron diffraction, soft x-ray photoemission, and cathodoluminescence (CLS) spectroscopies to investigate the effects of the GaAs(100) surface geometry and composition on the formation of electrically active interface states at Al-GaAs(100) contacts. Clean GaAs(100) surfaces in the 350 to 620°C annealing temperature range undergo large compositional, structural, and electronic changes with temperature. Aluminum thin film deposition induces new discrete deep level CLS features between ∼0.80 and 1.20 eV photon energy, whose properties depend sensitively and systematically on surface annealing temperature and/or reconstruction. Fermi level (EF) stabilization energies at these interfaces span the range from 0.58 eV above the valence band maximum (Ev) for an arsenic-rich starting surface to 0.46 eV above Ev for a gallium-rich starting surface. Correlation between the aluminum-induced deep level energies and the interface EF position suggests an important role of localized bandgap states in determining the interface barrier height. The sensitivity of these states to starting surface composition and reconstruction may open new possibilities for tailoring Schottky barrier properties. © 1993 The Mineral,Metal & Materials Society,Inc.