Ge-on-insulator lateral bipolar transistors

Abstract

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 V/JE 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 V/JE is attributed to recombination at the Ge/BOX interface in the emitter-base diode space-charge region.

Comparative Study of Different Configurations in Triple-Sided Charged Plasma Symmetric Lateral Heterojunction Bipolar Transistors on SOI

“…We are able to achieve the same collector current, say @ I C ≈ 2 μA/μm with an ∼320 mV smaller V BE by a device with a pure Ge base and an ∼158 mV smaller V BE by a device with 0.3Ge base with respect to the linearly graded SiGe base. This observation proves the scaling of V BE with E g of the base material …”

“…This observation proves the scaling of V BE with E g of the base material. 32 We also observe that at same V BE , the I B of the device with pure Ge base is shifted to the left the most. This is followed by a device with 0.3Ge base with respect to the device with a graded SiGe base.…”

“…Term n ieB 2 would be greater in the Si-Ge-Si configuration owing to the higher Δ E gB , but we know from Table that N B is highest for this device configuration from the other two device configurations. The Auger recombination coefficients of Si, SiGe, and Ge are very small and almost the same (∼10 –32 cm 6 /s for Si and SiGe and ∼10 –31 cm 6 /s for Ge). , Therefore, Auger recombination of the minority carrier lifetime in W B that comprises the base current component J B,rec is very small as compared to the other two components.…”

“…The Auger recombination coefficients of Si, SiGe, and Ge are very small and almost the same (∼10 −32 cm 6 / s for Si and SiGe and ∼10 −31 cm 6 /s for Ge). 26,32 Therefore, Auger recombination of the minority carrier lifetime in W B that comprises the base current component J B,rec is very small as compared to the other two components.…”