摘要
近年來，隨著通訊產業的快速發展，工業界以及學術界無不全力發展通訊IC，而在通訊系統中，最重要的骨架即是高頻微波元件。而隨著分子束磊晶(Molecular Beam Epitaxy)以及化學氣相沈積(CVD)的進步，製造出高品質的磊晶層已不是問題，故可生成品質良好之異質接面結構，而藉由能帶工程的改良，可製作出性能遠較同質接面雙載子電晶體(BJT)佳之矽鍺異質接面雙載子電晶體(SiGe HBT)，SiGe
HBT在射極-基極接面具有較高之射極注入效益；基極中由於有加速電場，故有較短之基極穿越時間(Base-Transient Time)，因此有較高之截止頻率fT(Cut-off Frenquency)，而隨著製程之進步，目前SiGe
HBT之截止頻率已可達350GHz以上。
在本篇論文中，首先回顧矽鍺異質接面雙載子電晶體(SiGe HBT)現有之能帶理論以及在電流 vs. 電壓所表現出來之特性。由於在基極區域之能隙大小比集極區域小，故在基極-集極接面處，將會有能帶不連續的情形，而由薛丁格方程式可得出傳導帶之能帶不連續△Ec將有兩量子能階的存在，因此當射極-基極順向偏壓Vbe偏壓在正常工作區間，然後掃瞄基極-集極超高反向偏壓Vcb，可發現在圖IC vs. Vcb以及IB vs. Vcb上將會有Current Jump的發生，此是因為量子能階上之電子穿遂至集極空乏區後，經由累增效應放大所形成，而我們分別在不同之射極-基極順向偏壓Vbe以及不同溫度條件下，分析此現象的改變。

Abstract
In this work, we first review the bandgap theory of the SiGe Heterojunction Bipolar Transistor (HBT), and it's current vs. voltage characteristics. Because the base region bandgap is smaller than that of collector region, so, it has bandgap discontinuity nearthe base-collector
junction. From the Schrodinger Equation, it can be derived
that two discrete quantum energy levels exist in the
conduction band discontinuity. When the emitter-base junction is forward biased by a voltage Vbe on the normal working region, then sweep the base-collector reverse biased voltage Vcb, We can find current jumps in the figure of IC vs. Vcb and IB vs. Vcb. This is because the electron in the discrete quantum energy level will penetrate to the
depletion region of the collector, then enlarged by the
multiplication effect. This effect is analyzed under different emitter-base forward bias voltage Vbe ,and under different temperatures.

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