E. Nebauer, M. Mai, E. Richter and J. Würfl

Published in:

J. Electron. Mater., vol. 27, no. 12, pp. 1372–1374 (1998).

Abstract:

The electrical properties of the ohmic contact systems Au/Pt/Ti/WSiN and Au/Pt/Ti to n⁺-InGaAs/GaAs layers grown by metalorganic vapor phase epitaxy were investigated and compared to each other. The thermal stability properties of these contact systems were characterized by accelerated stress tests at elevated temperatures and by complementary thin film x-ray diffraction analysis to evaluate the microstructural properties of degraded and nondegraded structures. The goal of these efforts was to develop stable, homogeneous emitter contacts for power heterojunction bipolar transistors. It was found that for both contact systems the best (specific) contact resistance R_c (ρ_c) is about 0.05 Ωmm (2 × 10⁻⁷ Ωcm²) in the as-deposited state. Au/Pt/Ti/WSiN contacts show no degradation after aging at 400°C for more than 20 h. This is in contrast to standard Au/Pt/Ti contacts which significantly degrade even after short time annealing at 400°C. The good long-time stability of the Au/Pt/Ti/WSiN system is related to the advantageous properties of the reactively sputtered WSiN barrier layer.

Keywords:

Diffusion barrier, InGaAs, heterojunction-bipolar transistor, ohmic contact

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