Pd/Si-based ohmic contacts to n-type InGaAs for AlGaAs/GaAs HBTs

Abstract

Pd/Si/Ti/Pt and Pd/Si/Pd/Ti/Au ohmic contacts to n-type InGaAs were investigated. In spite of the lower barrier height of the metal-InGaAs junction, as-deposited contacts showed non-ohmic behaviors due to the presence of insulating Si layer. However, the ohmic characteristics were considerably enhanced by rapid thermal annealing (RTA). In the Pd/Si/Ti/Pt contacts, the specific contact resistivity decreased to 1.7×10 −6 and 2.0×10 −6 Ω cm 2 by annealing at 375 °C/60 s and 425 °C/10 s, respectively. In the Pd/Si/Pd/Ti/Au contact, minimum specific contact resistivity of 3.9×10 −7 Ω cm 2 was achieved by annealing at 400 °C/20 s. However, it slightly increased to low-10 −6 Ω cm 2 by annealing at 400 °C for more than 30 s and to high-10 −7–low-10 −6 Ω cm 2 by annealing at 425–450 °C for 10 s. This resulted from the formation of Pd–Ga compounds. Good ohmic performance and non-spiking planar interface between ohmic materials and InGaAs were maintained after annealing at high temperature in both contact schemes. Theses thermally stable Pd/Si-based ohmic contact systems are promising candidates for compound semiconductor devices.