本論文研製和分析了氧化鎵覆蓋層於氮化鋁鎵/氮化鎵異質結構之紫外光檢測器。我們藉由許多方式提升拒斥比及降低暗電流以研製三波段紫外光檢測器。
起初，我們利用爐管熱氧化方式於氮化鋁鎵/氮化鎵異質結構上成長單斜氧化鎵層，並且製作成金半金雙波段光檢測器。成長120 nm厚單斜氧化鎵之光檢測器，其暗電流於1和10 V偏壓下分別為2.05 × 10-9和4.50 × 10-8 A。與無單斜氧化鎵層之光檢測器比較，暗電流可降低約四個數量級。具有120 nm厚單斜氧化鎵之雙波段紫外光檢測器， UV-B對UV-A於1 V偏壓下和UV-A對可見光於10 V偏壓下之拒斥比分別為80.53和311.95。
接著，我們將不同功函數之金屬應用於電極上。與鈦/鋁電極相比，具有較高功函數之鎳/金電極可降低暗電流，於1和10 V偏壓下分別為1.24 × 10-10和9.44 × 10-10 A。使用鈦/鋁電極和鎳/金電極之光檢測器，UV-C對UV-B於1 V偏壓下之拒斥比分別為8.90和39.54。因此使用鎳/金電極之光檢測器具有第三波段以應用於三波段紫外光檢測器。
最後，於成長單斜氧化鎵絕緣層時，將金奈米粒子參與其中並可視為催化劑。金奈米粒子可降低暗電流、增加粒子致光散射、增加UV-C對暗電流之電流比及增加UV-C對UV-B之拒斥比。使用鈦/鋁電極和鎳/金電極並具有金奈米粒子之光檢測器， UV-C對UV-B於1 V偏壓下之拒斥比分別為705.19和157.37。因此，使用鈦/鋁電極並具有金奈米粒子之光檢測器，UV-C對UV-B於1 V偏壓下具有最大之拒斥比，其值為705.19；使用鎳/金電極並具有金奈米粒子之光檢測器具有最小之暗電流，於1和10 V偏壓下分別為2.77 × 10-11和3.91 × 10-10 A。於本論文中，使用鈦/鋁電極和鎳/金電極並具有金奈米粒子之光檢測器最適合應用於三波段紫外光檢測器。

In this thesis, the fabrication and analysis of AlGaN/GaN heterostructure with a Ga2O3 cap layer ultraviolet (UV) photodetectors (PDs) were performed. We enhanced the rejection ratios and reduced the dark current by various methods so as to fabricate tri-band UV PDs.
First, the growth of β-Ga2O3 layer by furnace oxidation above AlGaN/GaN heterostructure and the fabrication of metal-semiconductor-metal (MSM) dual-band PDs have been reported. The dark current of the PD with a 120-nm-thick β-Ga2O3 layer were 2.05 × 10-9 and 4.50 × 10-8 A under 1 and 10 V applied bias, respectively. Compared to the PD without β-Ga2O3 cap layer, the leakage current could be effectively suppressed over 4 orders of magnitude by a thick β-Ga2O3 layer. The rejection ratios of UV-B to UV-A at 1 V and UV-A to visible light at 10 V of the dual-band UV PD with a 120-nm-thick cap layer were 80.53 and 311.95, respectively.
Second, we changed the electrodes of PDs with different work function metals. With higher work functions Ni/Au electrodes compared to Ti/Al electrodes, the dark current reduced to 1.24 × 10-10 and 9.44 × 10-10 A under 1 and 10 V applied bias, respectively. The rejection ratios of UV-C to UV-B under 1 V applied bias of the PD with Ti/Al electrodes and Ni/Au electrodes were 8.90 and 39.54, respectively. The PD with Ni/Au electrodes had the third band to cater to tri-band UV PD applications.
Finally, the β-Ga2O3 insulating layer was grown with Au nanoparticles which served as catalyst. PDs with Au nanoparticles could reduce the dark current, increase the particles-induced light scattering, enhance the current ratio of UV-C to dark current and enhance the rejection ratio of UV-C to UV-B. The rejection ratios of UV-C to UV-B under 1 V applied bias of the PD with Au nanoparticles with Ti/Al electrodes and Ni/Au electrodes were 705.19 and 157.37, respectively. Hence, the PD with Au nanoparticles with Ti/Al electrodes had the largest rejection ratio of UV-C to UV-B under 1 V applied bias of 705.19 while the PD with Au nanoparticles with Ni/Au electrodes had the smallest leakage current of 2.77 × 10-11 and 3.91 × 10-10 A under 1 and 10 V applied bias, respectively. The PD with Au nanoparticles with Ti/Al electrodes and Ni/Au electrodes were the best choices to cater to tri-band UV PD applications in this thesis.

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