On the optimization and reliability of ohmic and Schottky contacts to InAlAs/InGaAs HFET

Abstract
Performance and reliability issues of contacts to lattice matched HFETs (heterostructure field-effect transistors) grown by MBE (molecular-beam epitaxy) on InP are addressed. Based on the idea that both Ni and Ge should be very close to the semiconductor surface, a novel Au-Ge-Ni superlattice ohmic-contact metallization has been developed (R/sub C/<0.1 Omega -mm). The leakage current of reverse-biased Schottky contacts is studied experimentally and theoretically. It is shown by both methods that the undoped barrier layer thickness has a superior influence in comparison to the barrier height Phi /sub B/. If Schottky contacts are thermally stressed in the atmosphere (T=200 degrees C), a dramatic increase of leakage is observed while the barrier height Phi /sub B/ remains unchanged.

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