In this study, the operation of npn-type GaN-based heterojunction bipolar transistors with different net acceptor concentrations in p-base regions was simulated. It was confirmed that there is a critical net acceptor concentration (NA-ND) depending on the thickness of the base region and that if the NA-ND is lower than the critical value, the collector current may anomalously increase, regardless of base current injection. This phenomenon is caused by the punch-through process via the depletion layer extending from the collector–base junction. The effect of the valence band energy offset at the emitter-base heterojunction (ΔEV) on the current gain (β) was also investigated, and the results showed that β peaks when ΔEV is 0.22–0.30 eV. This is determined by the balance between the hot-electron injection and thermal diffusion processes in the electron transport from the emitter to the base.
Simulation analyses of carrier dynamics in npn-type GaN-heterojunction bipolar transistors with different hole-concentration p-base layers
Akira Mase, Yusuke Iida, Masaya Takimoto, Yutaka Nikai, Takashi Egawa, Makoto Miyoshi; Simulation analyses of carrier dynamics in npn-type GaN-heterojunction bipolar transistors with different hole-concentration p-base layers. J. Vac. Sci. Technol. B 1 September 2023; 41 (5): 052206. https://doi.org/10.1116/6.0002577
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