變溫下異質接面雙載子電晶體模型之建立

Abstract

異質接面雙載子電晶體的電性行為對溫度是非常相依的，將會嚴重影響整體電路的操作和元件本身的可靠度，本論文中將比較不同半導體材料接面對溫度的敏感度，他們對溫度的關係非常明顯的不同，砷化鋁鎵異質接面雙載子電晶體在溫度升高時，電流增益迅速下降，相反的，磷化銦鎵異質接面雙載子電晶體則變化不大，主要的原因在於價電帶不連續能障的高低，若價電帶能障低則反向入射基極電流在高溫下變化非常大，基極電流急遽升高造成電流增益的下降，因此，磷化銦鎵元件具有較高的溫度穩定性，這就是為什麼磷化銦鎵電晶體優於砷化鋁鎵電晶體的原因。 本論文主要是以元件物理分析建立起異質接面雙載子電晶體之模型，並發展出一套不同的變溫參數粹取方式，可粹取之直流參數包括導電帶不連續能障、價電帶不連續能障、基極電子漂移速度與電子等效質量，可粹取之小訊號參數包括集極空乏區之電子漂移速度與基極-集極空乏區電容。 最後，我們比較變溫實驗量測之數據與模型模擬，結果是非常令人滿意的，研究在變溫下元件直流與高頻電性行為，我們相信本論文研究能提供檢視異質接面雙載子電晶體特性以達到元件最佳效能。

The significant temperature dependence of the HBTs’ electrical characteristics has a strong impact on the circuit performance and the reliability of devices. From the comparison of temperature stability with InGaP HBTs and AlGaAs HBTs, it is clear they are very different. The current gain of the AlGaAs HBTs drops quickly as increasing the temperature; however, the current gain of InGaP HBTs does not change very much. Due to the small valence band energy barrier at the heterojunction of AlGaAs/GaAs, the back injection will be very important especially at high temperatures. And because the increased back injection makes current gain drops, the InGaP HBTs have the best temperature stability. It is why InGaP HBTs are better than AlGaAs HBTs. The purpose of this thesis is mainly to build up the HBTs’ model by analysis of device physics and to develop a new extraction method for device parameters. We could extract important parameters for DC operation, such as conduction band energy discontinuity, valence band energy discontinuity, electron mobility in base, and electron effective mass of emitter material. Furthermore, we could also extract parameters for RF operation, such as base-collector junction capacitance and electron saturation drift velocity in the base-collector depletion region. Finally, the results of this model were also verified by the comparison with the experimental measurement data and the simulation results. Excellent agreement was obtained. From the research of HBTs’ DC and RF behavior under variant temperature, we believe this thesis can offer a method to qualify the fundamental properties of HBTs for different materials to achieve the optimum performance.