摘要
本論文利用分子束磊晶(Molecular Beam Epitaxy, MBE)成長磷化銦鎵/砷化鎵平面摻雜異質接面雙極性電晶體(InGaP/GaAs δ doped HBT)，利用平面摻雜(δ doped)技術提昇基極的金屬-半導體之歐姆接觸特性，降低基極之串聯阻抗，進而提高功率增益截止頻率或最大振盪頻率(fmax)，並利用平面摻雜技術對基極區域電位的調變(potential modulation)，內建基極區域之加速電場，降低載子穿越基極之傳輸時間，進而提高截止頻率(cut-off frequency, ft)。
首先比較具有空間層(spacer)及平面摻雜的磷化銦鎵/砷化鎵異質接面雙極性電晶體(InGaP/GaAs HBT)與一般磷化銦鎵/砷化鎵異質接面雙極性電晶體之直流特性差異，並針對基極之歐姆接觸做進一步的探討。
在基極與未摻雜(undoped)之空間層間加入平面摻雜，調變基極金屬電極與基極半導體間之電位與雜質濃度，可以有效改善基極金屬電極的特徵電阻值(ρC)，其值約在10-4 ~ 10-5 (Ω-cm2)，證明平面摻雜對金屬與半導體接面歐姆接觸特性有顯著的提昇。
由射極-基極接面的電特性量測，具有空間層及平面摻雜之磷化銦鎵/砷化鎵異質接面雙極性電晶體(A結構)之起始電壓(Vturn-on)約1.45V，而一般不具空間層及平面摻雜的磷化銦鎵/砷化鎵異質接面雙極性電晶體(B結構)只有1.1V，可了解平面摻雜對此異質接面具有顯著的電位調變作用；此外，A結構明顯有較高的漏電流，在-2V時約數十個nA，而B結構只有數個nA。
於梗美樂-普恩繪圖(Gummel-Poon Plot)量測中，由於A結構之射極-基極有較大的漏電流，所以其電流增益約只有4，而B結構之電流增益約40；A結構主要是靠載子穿隧(tunneling)效應為電流成分，故理想因子η > 2，而B結構η接近於1，是以晶體復合電流(IB,bulk)為主要成分。
而在共射極電流增益(IC-VCE)量測中，兩個結構都不受歐利效應(Early effect)之影響，表示基極-集極接面濃度分佈相當陡峭(abrupt)。萃取補償電壓(VCE,offset)可以得到A結構約0.55V，B結構約0.15V，平面摻雜之電位調變在此得到應證。

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