Ge-on-insulator lateral bipolar transistors

We report the first demonstration of thin-base symmetric lateral NPN bipolar transistors built on 8-inch Ge-on-insulator (Ge-OI) wafers. A Ge-OI device can achieve the same collector current as a Si-OI device but at ~ 460 mV lower VBE due to the bandgap of Ge being 460 meV smaller than that of Si. Lower operation voltage should translate directly into lower power dissipation. CMOS-like process was used to fabricate lateral Ge-OI bipolar transistors. The measured collector and base currents are examined and compared with those of Si-OI and SiGe-OI devices to shed light on process-related device physics. The large observed base current at small VBE is attributed to recombination at the Ge/BOX interface in the emitter-base diode space-charge region.