Interface-state density analysis of thermally and electron-beam-annealed GaAs surfaces

Abstract

Schottky diodes were formed on n-GaAs surfaces that had undergone furnace and scanned electron beam (SEB) heat treatments that are similar to those typically used for Ohmic contact formation. The diode parameters of heat-treated samples were inferior to those that were not heat treated. The interface-state density Dit, determined from Tseng and Wu’s interfacial layer model, was found to exhibit a strong correlation with the heat treatments, with furnace-annealed samples exhibiting progressively larger Dit values than SEB annealed samples. The presence of a spin-on glass capping layer during heat treatment resulted in reduced Dit values. Photochemical passivation of the GaAs surface before Schottky metal deposition resulted in a reduction in the interface-state density. Controlled etching of a heat-treated GaAs surface revealed that the surface damage caused by heat treatments extends to about 500 nm. Elevated thermal aging studies of Schottky contacts show a monotonic increase in Dit with aging time, irrespective of surface preparation.