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

摘要

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 deg C/60 s and 425 deg C/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 deg C/20 s. However, it slightly increased to low-10~(-6) OMEGA cm~2 by annealing at 400 deg C for more than 30 s and to high-10~(-7)-low-10~(-6) OMEGA cm~2 by annealing at 425-450 deg 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.