Abstract
A detailed study on the microstructural changes that occur on annealing of Au/Pt/Ti ohmic contacts to n-type InGaAs has been carried out. The metal layers were deposited sequentially by electron beam evaporation onto InGaAs, doped with Zn to a level of 7 × 1018 cm−3, that was epitaxially grown on < 100 > InP substrates. The deposition sequence and metal layer thicknesses were: Ti (25 or 30 nm), Pt (25 or 30 nm) and Au (250 or 300 nm). Samples were annealed at temperatures ranging from 250–425 ‡C in a nitrogen atmosphere. As-deposited contacts were Schottky barriers, while a minimum contact resistance of 2 × 10−5 Ω cm2 was obtained by annealing in the 375–425 ‡C range. Annealing resulted in the inward diffusion of Ti and outward diffusion of In and As, leading to the formation of TiAs, metallic In and Ga-rich InGaAs at the Ti/InGaAs interface. The Pt diffusion barrier was effective in preventing In diffusion into the outer Au layer and minimizing Au diffusion to the semiconductor.
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Ivey, D.G., Jian, P., Bruce, R. et al. Microstructural analysis of Au/Pt/Ti contacts to p-type InGaAs. J Mater Sci: Mater Electron 6, 219–227 (1995). https://doi.org/10.1007/BF00187201
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DOI: https://doi.org/10.1007/BF00187201