| Summary: | 碩士 === 國立雲林科技大學 === 電子與資訊工程技術研究所 === 86 === AlGaAs/GaAs heterojunction bipolar transistors(HBTs) have great potential in m icrowave power applications. Significant progress has beenmade since 1987. Because the thermal conductivity of GaAs is poor(only 1/3 of that of Si), device temperature will be increased significantly under high power operation, which in turn limits the device performance. The thermal effect degrades the upper limit of the HBT power capability more than the electric effect does. To improve the power handling capability, most power HBTs have interdigitated or multi-finger emitter layout design. However, temperature distribution among fingers is usually not uniform, which results in the "local hot spot" and a sudden drop in device current gain. This phenomenon degrades the device power performance and long-term reliability.The objective of this thesis was to investigate the thermal-electrical characteristics of AlGaAs/GaAs HBTs for high power applications. To improve the thermal stability on multi-finger HBTs, a new structure with unequal finger spacings is proposed. In this new design, finger spacing is varied in such a way that a uniform temperature distribution can be achieve d. The "local hot spot" can be avoided, and the current gain can be enhanced. The design is valid at different biases and contact resistance values. In this thesis, all of the results are simulated by using the two-dimensional device simulator Medici and three-dimensional device simulator Davinci.
|
|---|
