我們實驗室於2006年提出一種以銻砷化銦鎵(InGaAsSb)為基極的異質接面雙載子電晶體，此種電晶體不但具有低導通電壓及低位移電壓，亦有優秀高頻特性。為了將此元件頻率提升至terahertz(THz)，提升製程技術將元件尺寸縮至奈米線寬是必須的過程，然而此時元件的表面復合電流(surface recombination current) 與金屬/半導體接面阻值將同時增加，因而限制了縮減尺寸所帶來高頻特性提升之好處。本論文專注於探討銻砷化銦鎵基極材料對射極尺寸效應(emitter size effect)與其歐姆接觸特性的影響。 本研究藉由製作不同射極周長/射極面積比之元件，萃取InAlAs/InGaAsSb/InGaAs 異質接面雙載子電晶體的射極周圍復合電流密度(KB,surf)，證實銻砷化銦鎵材料具有低表面復合速率。使得元件在passivation前後其直流特性相似，此外，無論使用自我校準(self-aligned)或是非自我校準(non-self-aligned)的製程，元件中的KB,surf 亦無太大變異，證明銻砷化銦鎵基極元件在縮小元件時較不受射極尺寸效應影響，進而維持其電流增益。 在銻砷化銦鎵材料中，藉由提高摻雜濃度與增加銻含量，其特徵接觸電阻可低於5×10-8 ?-cm2。根據此研究顯示，銻砷化銦鎵基極異質接面電晶體擁有低基極接觸電阻及低表面復合速度，這些優越特性有助於發展THz電晶體。 A novel heterojunction bipolar transistor (HBT) with an InGaAsSb base was proposed and demonstrated by this group in 2006.This novel transistor not only has low turn-on voltage and low offset voltage but also has excellent radio-frequency performance. In order to increase the cut-off frequency to terahertz, scaling down the emitter width to one hundred nanometers or below is necessary. However, both surface recombination current and contact resistance might increase and degrade the device’s performance at these physical dimensions.. In this work, efforts are focused on studying the emitter size effect (ESE) in InGaAsSb base DHBTs and ohmic contact on p-InGaAsSb. We extract the emitter periphery surface recombination current density (KB,surf) in the InAlAs/InGaAsSb/InGaAs double heterojunction bipolar transistor (DHBT) from the devices with different PE/AE ratio. We verified that InGaAsSb has low surface recombination velocity. Moreover, the passivation-free characteristics and the similar KB,surf in self-aligned and non-self-aligned devices confirm the superiority of InGaAsSb base HBT for aggressive scaling. Contact resistance is one of the most important parasitic elements that determine the device performance, especially for the submicron HBTs. Low specific contact resistance (<5×10-8 ?-cm2) has been achieved on heavily Be-doped high Sb-content InGaAsSb bulk samples. This work shows that the InGaAsSb base DHBT has low contact resistance as well as low surface recombination velocity indicating that InGaAsSb base DHBT has great potential for THz devices.
