Ni/Pd/Au ohmic contact for p-GaAs and its application in red RCLED

Abstract

The multi-layered Ni/Pd/Au metal structure is investigated through the TLM method and surface morphology inspection to study the feasibility of forming a p-type ohmic contact for p-GaAs material and its application in red RCLED in this report. Experimental results indicate that the annealing temperature for obtaining the lowest specific contact resistivity ( ρ c) is decreased with the increase of Pd layer thickness and remains unchanged as long as adequate Pd layer thickness is maintained. Additionally, an optimum metallurgical structure of Ni(80 nm)/Pd(120 nm)/Au(200 nm) with a considerably low ρ c ∼ 2 × 10 −6 Ω cm 2 can be obtained after annealing at 300 °C for 1 min. This is more than one order of magnitude improvement over that of the Ti/Pt/Au system. With the optimum metallurgical structure, the annealing temperature for obtaining better ohmic contact characteristic can be selected from a relatively low temperature range 280–350 °C. Furthermore, when this p-type ohmic metal structure Ni/Pd/Au is deposited on red RCLED as p-type ohmic contact, both I– V and P– I characteristics of RCLED show significant improvement as compared with those of RCLED having the conventional Ti/Pt/Au metal contact.