Crystallographic microstructure and electrical characteristics of Au/Pt/Ti/Ni ohmic contacts on <i>p</i>-type (001) ZnTe layers

Abstract

The crystallographic microstructure and electrical characteristics of Au/Pt/Ti/Ni ohmic contacts on p-type (001) ZnTe layers are investigated as a function of annealing temperature, by using the transmission line model method, cross-sectional transmission electron microscopy, and Auger electron spectroscopy. The specific contact resistance decreases when the annealing temperature is increased and reaches a minimum at 300 °C. A minimum value of 1.1×10−6 Ω cm2 is obtained for a hole concentration of 3×1019 cm−3. The epitaxial NiTe2 that formed at the metal/semiconductor interface due to annealing is considered to play an important role in lowering the contact resistance. The excess Zn atoms created by the reaction between Ni and ZnTe are found to diffuse upward and to segregate at the Pt/Ni interface. A contact stability test performed at 102 °C suggests that these ohmic contact structures are stable even under high-current injection.