| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 93 === Study of InGaP/GaAs Tunnel-Collector HBT with Compositionally Graded Base
Chuan-Hao Lu* Wei-Chou Hsu**
Institute of Microelectronics, Department of Electrical Engineering
National Cheng Kung University,Tainan,
Taiwan, R.O.C.
Abstract
In this thesis, we fabricated InGaP/GaAs heterojunction bipolar transistors with indium compositionally graded base and tunnel-collector layer by MOCVD system. Experimental results show that the offset voltage reduces from 130 mV to 25 mV, and knee voltage reduces from 910 mV to 400 mV due to the asymmetry of base-emitter (B-E) and base-collector (B-C) junctions is eased by the addition of tunnel-collector layer. Furthermore, tunnel-collector structure also has less temperature sensitivity due to the variations in current gain is below 5% compared to 35% of SHBT at temperature from 300 K to 450 K at current density of 20 kA/cm2. This reveals excellent thermal stability characteristic. In RF performance, the indium compositionally graded base makes fT rise from 37 GHz to 44 GHz and fmax increase from 40 GHz to 53 GHz. This improvement is mainly resulted from the build-in electrical field (shorter base-transient time) and smaller base resistance (RB).
* Author
** Advisor
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