Laser-induced chemical reactions at the Al/III-V compound semiconductor interface

Abstract

We have used pulsed laser annealing to promote and characterize highly localized chemical reactions at Al interfaces with III-V compound semiconductors. At successive stages of these laser-induced reactions, we have monitored atomic movement and chemical structure on a microscopic scale using soft x-ray photoemission spectroscopy and Auger electron spectroscopy. For Al on each of the six III-V compound semiconductors investigated, we have found a finite range of energy density above a characteristic threshold energy density such that a chemical reaction is produced without disrupting the surface morphology. The systematic change of threshold with different semiconductors indicates a thermally activated reaction occurring in the molten phase of the Al overlayer and a thin substrate layer. Heat flow calculations, which model the temperature profiles during and after the laser pulse, confirm this model and also account for the highly abrupt interface between the reacted ternary overlayer and the binary substrate. The excellent agreement between experiment and theory demonstrates that thermal properties of the semiconductor have a dominant influence on the interfacial temperature profile and threshold energy density for reaction.