- 學位論文
砷化鋁鎵/砷化鎵異質接面雙載子電晶體之硫化處理特性之研究
The Study on Effects of AlGaAs/GaAs Heterojunction Bipolar Transistor with Ammonium Sulfide Treatment
摘要
中文摘要 由於砷化鋁鎵/砷化鎵異質接面雙載子電晶體具有優異的電流增益、操作速度以及其低電壓動作等特性，因此特別適合應用於微波、高功率及低電壓的操作系統，但是由於砷化鋁鎵/砷化鎵異質接面雙載子電晶體常應用於高功率密度環境及本身砷化鎵材料之低熱導係數影響，使得元件操作時外界與元件自身所產生的熱無法完全經由基板散逸至外界，使得元件之特性衰退；加上該材料的高表面複合速率(約106 cm/s)卻也導致漏電流過大，並直接降低其電流增益，因此探討元件之熱效應問題以及藉由一表面披覆處理以降低元件的表面複合，是迫切需要解決的問題。 我們成功地製作了砷化鋁鎵/砷化鎵異質接面雙載子電晶體，其中射極、基極及集極歐姆接觸電阻均可以達到10-6 W-cm2，而電流增益則可以達到100以上；並發現其熱效應問題，而砷化鋁鎵/砷化鎵異質接面雙載子電晶體在經過硫化處理後，我們利用光學顯微鏡、電子顯微鏡、原子力顯微鏡、X光頻譜分析儀及歐傑頻譜分析儀等設備，分析其表面與材料特性的變化，並利用半導體參數分析儀與網路分析儀等設備分析元件之直流與射頻特性。最後我們發現，在物性分析方面硫化處理改善砷化鎵表面狀況，並證明硫化效應是一擴散效應，隨硫化時間增加而擴散至更深處，而在電性方面，硫化處理過後之電晶體因散熱面積部份減少故其溫度影響電晶體導致電流衰退的效應更加的明顯，且射極面積也影響了散熱效率，射極面積大的散熱較快，較射極面積小的不易累積熱量於電晶體中，另一方面，硫化效應可以改善砷化鋁鎵/砷化鎵異質接面雙載子電晶體之直流特性，然而因基極電阻增加而其交流特性卻也因此劣化。
並列摘要
Abstract Because of the high-current gain, operation speed, and low switch on voltage of the AlGaAs/GaAs Heterojunction Bipolar Transistors (HBTs), especially to applicate in microwave, high power, and low bias systems, but many applications will require HBTs to operate in high power density environments, the device performances were decaded because of the heat which created by itself and extrinsic environments that the heat can not dissipated to air from substrate due to the low thermal conductivity of the GaAs materials; except to the effect of thermal, the weakness of the AlGaAs/GaAs HBTs is the high surface recombination velocity (about 106 cm/s) that before the oxide layer deposited. In the thesis, an AlGaAs/GaAs HBT was fabricated; the Emitter, Collector and Base characteristic resistances could be 10-6 W-cm2, and the current gain b can to 100. To observe the surface state with optic-microscopy, SEM, and AFM, the surface state has became better after ammonium sulfide treated; analysis the surface components with XPS and the diffusion effect was proved by AES; the thermal effect was discussed, the current and current gain were decaded because the sulfide layer reduce the heat dissipated to air. The DC performance was improved by ammonium sulfide treated because of the surface passivation effect, however the RF performances were reduced, because of the sulfide effect is a diffusion effect and increased the base resistance.