Related Electrical and Metallurgical Properties of Pd/Zn/Pd/Ge and Pd/Zn/Pd/Au Contact Systems to p-InGaP

The comparison of electrical and metallurgical properties of vacuum-evaporated Ge/Pd(Zn) and Au/Pd(Zn) contact metallizations to moderately doped p-type InGaP epitaxial layers (p ≈ 2 × 1018 cm—3) is presented. The Pd/Zn/Pd/Ge contacts exhibited Ohmic behaviour already from 400 °C and their specific contact resistance dropped to 4 × 10—5 Ω cm2 when annealed at 490 °C. Cross-sectional transmission electron microscopy and energy dispersive X-ray spectrometry demonstrated that a relatively sharp and nonspiking contact–InGaP interface has still been preserved at this high temperature. On the other hand, regardless of the excellent electrical properties (ϱc = 5 × 10—6 Ω cm2 at 490 °C) of the Pd/Zn/Pd/Au contacts, strong metallurgical reactions at the contact–InGaP interface at temperatures ≥450 °C resulted in an extensive decomposition and melting of the interface area with deep protrusions into the InGaP.