- 學位論文
以III族氮化物之光電及聲電特性研製紫外光感測器
Fabricaion study of UV detectors using the opto-electrical and acoustic characteristics of III-nitride thin films
摘要
本論文利用三族氮化物中具有良好光電及聲電特性之氮化鋁及氮化鎵材料研製直流及交流紫外光偵測器。直流型式為金屬-半導體-金屬結構，而交流型式為表面聲波振盪器。 在p型氮化鎵金屬-半導體-金屬光偵測器中，元件暗電流在偏壓20V時，其值為10.1pA，響應度在5V時可達0.1A/W，UV/visible ratio約2.5個order。最低可偵測之光功率約為10nW。 利用低溫迴旋濺鍍法在氮化鎵/藍寶石基板上沉積之氮化鋁研製金屬-半導體-金屬光偵測器，其偏壓於20V時，暗電流為670fA。使用小功率氘燈照射元件，光暗電流即有1個order之差別。 表面聲波振盪器方面，研製AlN/GaN/Sapphire及GaN/Sapphire層狀結構之光偵測器。AlN/GaN/Sapphire表面聲波元件之中心頻率為166.4MHz，插入損耗為-21.627dB，旁帶抑制為19.5dB。GaN/Sapphire表面聲波元件之中心頻率為157.3MHz，插入損耗為-27.7dB，旁帶抑制為14.5dB。由於AlN/GaN/Sapphire表面聲波特性皆優於GaN/Sapphire，因此也較容易製作表面聲波振盪器。在光感測方面，兩個結構皆光功率對振盪頻率漂移皆呈線性關係，因此也適合作光偵測器。 最後，利用三族氮化物結合上述兩種元件，可發展出一種新型的MSM+SAW光偵測器，此元件不但有潛力量測更精準之光功率外，更擁有可分辨不同紫外光波段之能力，此部份目前正申請專利中。
並列摘要
In this thesis, III-nitride materials, AlN and GaN, which uniquely present at the same time the excellent electronic, optoelectronic and acoustic properties, were employed to fabricate MSM photodetectors & SAW oscillators for UV detection. The dark current of Al/p-GaN MSM photodetector is 10.1pA at 20V, the photoresponsivity is 0.1A/W at 5V, the UV/visible ratio is approximately 2.5 orders, and minimum detectable power is probably 10nW. AlN MSM photodetectors were fabricated on AlN epitaxial thin film deposited on GaN/Sapphire using helicon sputtering system at the low temperature of 300°C. The dark current of the device is 670fA at 20V and photo current illuminated by D2 lamp is higher by one order. The characteristics of SAW devices on AlN/GaN/Sapphire and GaN/Sapphire and the characteristic frequency responded to the UV illumination were explored. Superior SAW properties in terms of insertion loss and sidelobe rejection have been obtained for the SAW devices made on AlN/GaN/Sapphire, compared to those of the ones made on GaN/sapphire. With the deposition AlN on GaN/Sapphire, it can help ease off the fabrication difficulties of SAW oscillators. The illumination effect on the SAW oscillators has been investigated. It showed a linear relationship between the radiation power and the frequency shift of oscillation for GaN/Sapphire and AlN/GaN/Sapphire SAW oscillators, indicating the feasibility for UV sensors. Finally, I have proposed a novel idea of UV detectors that combines the III–Nitrides SAW and MSM devices. The devices not only have the potential to measure optical power more accurately, but also have feasibility of tailoring the UV absorption edge of wavelength. The patent of this invention is pending now.