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

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 x 10(-6) and 2.0 x 10(-6) Omega cm(2) by annealing at 375 degreesC/60 s and 425 degreesC/10 s, respectively. In the Pd/Si/Pd/Ti/Au contact, minimum specific contact resistivity of 3.9 x 10(-7) Omega cm(2) was achieved by annealing at 400 degreesC/20 s. However, it slightly increased to low-10(-6) Omega cm(2) by annealing at 400 degreesC for more than 30 s and to high-10(-7)-low-10(-6) Omega cm(2) by annealing at 425-450 degreesC 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. (C) 2003 Elsevier B.V. All rights reserved.