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A Gold-Free Fully Copper-Metallized InP Heterojunction Bipolar Transistor Using Non-Alloyed Ohmic Contact and Platinum Diffusion Barrier

A gold-free, fully Cu-metallized InP heterojunction bipolar transistor using non-alloyed Ti/Pt/Cu and Pt/Ti/Pt/Cu ohmic contacts and platinum diffusion barrier has been successfully fabricated. The InGaAs/Ti/Pt/Cu ohmic structure was stable after annealing up to 350°C as judged from the Auger depth profiles. A current-accelerated stress test was conducted on the device with a current density JC=80 kA/cm2 for 24 h, and the current gain showed no degradation after the current stress. The devices were also thermally annealed at 200°C for 3 h and showed almost no change in the electrical parameters after the heat treatment. The results show that the Au-free, fully Cu-metallized InP heterojunction bipolar transistor (HBT) can be realized using non-alloyed ohmic contacts and Pt diffusion barrier.