本論文主要著重在鎵系列半導體，包含氮化鎵與氧化鎵之成長，並且研製和分析氮化鎵與氧化鎵系列紫外光檢測器。
首先在氮化鎵系列紫外光檢測器方面，我們應用氮化鋁銦覆蓋層或插入層來製作氮化鎵光檢測器。所成長的氮化鋁銦薄膜的鋁含量被控制在17-18%，這樣的氮化鋁銦薄膜其晶格常數與氮化鎵匹配。與傳統的的蕭基能障光檢測器相比，藉由加入覆蓋層或插入層可以降低暗電流值、增加紫外光與可見光的拒斥比及紫外光檢測率。這樣的結果可以歸因於覆蓋層可以提供一個較大與較厚的蕭基能障，且對氮化鎵的表面形態有鈍化的作用，對於插入層的氮化鎵光檢測器而言，插入層可以有效的阻擋差排缺陷延伸至氮化鎵表面。在-5V的偏壓下，具有氮化鋁銦覆蓋層及具有氮化鋁銦插入層的光檢測器之拒斥比分別為4244與2874。其中也發現傳統的光檢器，具有氮化鋁銦覆蓋層及具有氮化鋁銦插入層的光檢測器之檢測度分別為1.12×109, 4.42×1011 與 9.53×1010 cmHz0.5W-1。
在氧化鎵系列紫外光檢測器研製方面，我們使用爐管熱氧化的方法於氮化鎵磊晶薄膜上成長氧化鎵薄膜。從X光繞射分析中，1000、1025、1050與1100℃成長的氧化鎵薄膜的半高全寬分別為0.36、 0.33、0.31與0.29度。隨著成長溫度增加，氧化鎵薄膜的品質變的較好。在260nm的光照與-5V的偏壓下，1000、1025、1050與1100℃成長的氧化鎵薄膜所組裝的檢測器其光響應值分別為0.453, 0.182, 0.036與0.039 A/W。同時也發現所有組裝的氧化鎵檢測器其紫外光對可見光的拒斥比皆非常大，其中，1000℃成長的氧化鎵薄膜所組裝的檢測器其拒斥比達六個數量級。同時我們也組裝了氧化鎵/氮化鎵異質結構之solar-blind與visible-blind雙帶紫外光檢測器。藉由簡單的改變操作偏壓，我們能夠控制半導體的空乏層深度，因此能夠轉換solar-blind或visible-blind的操作模式。為了偵測更短波長的真空紫外光，我們也使用氮化鋁鎵磊晶薄膜熱氧化成長氧化鋁鎵，同時組裝氧化鋁鎵真空紫外光檢測器。所組裝的氧化鋁鎵真空紫外光檢測器其截止波長為220nm。在-1V的偏壓與220nm的光照下所量測到的光響應值為0.052 A/W，對應到30%的外部量子效率，同時紫外光與可見光拒斥比達到四個數量級。這樣的結果說明了所組裝的真空紫外光檢測器的實用性。
基於上述的結果，我們進一步使用vapor-liquid-solid方法成長單斜氧化鎵奈米線並組裝氧化鎵奈米線的solar-blind光檢測器。氧化鎵奈米線的平均長度與直徑隨著成長溫度增加而增加。所組裝的氧化鎵奈米線紫外光檢測器其截止波長為255nm。在10V的偏壓與255nm的光照下所量測到的光響應值為0.8 mA/W。在5V的偏壓下，雜訊等效功率與檢測度分別為7.63×10-10 W 與8.69×109 cmHz0.5W-1。同時，我們也組裝氮化鎵奈米線紫外光檢測器。透過氮化反應，我們成功的將氧化鎵奈米線氮化成氮化鎵奈米線。與傳統的薄膜式氮化鎵光檢測器相比，氮化鎵奈米線光檢測器之光電流比薄膜式光檢器的光電流大一千倍。在5V的偏壓與360nm的光照下，所量測到氮化鎵奈米線光檢測器與薄膜式氮化鎵光檢測器的光響應值分別為70.4 與 0.12 A/W。同時，氮化鎵奈米線光檢測器的紫外光與可見光拒斥比也比薄膜式氮化鎵光檢測器的拒斥比大。這樣的結果也說明所組裝的氮化鎵奈米線紫外光檢測器，有好的實用性。

The main goal of this dissertation is the fabrication and analysis of GaN and Ga2O3-based ultraviolet (UV) photodetectors (PDs).
First, we apply in-suit grown AlInN cap layer or intermediate layer to the fabrication of the GaN-based PDs. The AlInN films were grown lattice matched to GaN with an indium content of ~17-18%. Compared with conventional Schottky barrier PDs without AlInN cap layer or intermediate layer, it was found that we can achieve significantly much smaller dark current, larger UV-to-visible rejection ratio and larger normalized detectivity by inserting the AlInN cap layer or intermediate layer. These results could be contributed to the thicker and higher potential barrier and effective surface passivation for the insertion of AlInN cap layer and the effective suppression of threading dislocation by the AlInN intermediate layer. With a -5 V reverse bias, it was found that the UV-to-visible rejection ratio were 4244 and 2874 for PDs with a semi-insulating AlInN cap layer and intermediate layer, respectively. With a -5 V reverse bias, it was also found that normalized detectivity for conversional PD, PDs with AlInN cap layer or intermediate layer were 1.12×109, 4.42×1011 and 9.53×1010 cmHz0.5W-1, respectively.
On the part of Ga2O3 UV PDs, we report the growth of β-Ga2O3 thin films by furnace oxidation of GaN epitaxial layer at high temperature in oxygen containing ambient. It was found that the full width of half maximum (FWHM) of the β-Ga2O3 films of XRD peak were 0.36, 0.33, 0.31 and 0.29 degree when the grown temperature was 1000, 1025, 1050 and 1100℃, respectively. The FWHM of β-Ga2O3 films grown at low temperature was larger than that at high temperature. Solar-blind β-Ga2O3 PDs was also fabricated by depositing interdigitated contact electrodes. With an incident light wavelength of 260 nm and an applied bias of 5 V, it was found that measured responsivities of the PDs was 0.453, 0.182, 0.036 and 0.039 A/W for the β-Ga2O3 grown at 1000, 1025, 1050 and 1100℃, respectively. It was found that the fabricated PDs exhibits extremely large deep-UV-to-visible rejection ratio. The responsivity measured at 260 nm was 6 orders of magnitude larger than that measured at 400 nm for the β-Ga2O3 PD grown at 1000℃. A β-Ga2O3/GaN hetero-structured solar-blind and visible-blind dual bands PD was also fabricated. It was found that we could control the depletion depth of the device and thus switch the operation mode between solar-blind and visible-blind by simply changing the applied bias. For the detection of vacuum ultraviolet (VUV) light, (AlxGa1-x)2O3 thin films grown by furnace oxidation of Al0.24GaN epitaxial layer have been studied. An (AlxGa1-x)2O3 VUV PD was also fabricated. It was found that cutoff occurred at around 220 nm for the fabricated (AlxGa1-x)2O3 PD. The 0.052 A/W responsivity measured at 220 nm biased at 1 V for the (AlxGa1-x)2O3 PD corresponds to a 30% external quantum efficiency. As we switched the UV excitation on and off, it was found that dynamic response of the (AlxGa1-x)2O3 PD was stable and reproducible with an on/off current contrast ratio of around 103. The responsivity measured at 220 nm was 4 orders of magnitude larger than that measured at 400 nm. The extremely large deep-UV-to-visible rejection ratio and rapidly transient response indicate that the (AlxGa1-x)2O3 PD fabricated in this study is potentially useful for VUV sensing.
Based on the aforementioned, we also grow the β-Ga2O3 nanowires (NWs) by heating the GaN/sapphire template with various temperatures. The β-Ga2O3 NWs were grown with a vapor-liquid-solid mechanism. The average diameter and average length of the nanowires both increased as we increased the growth temperature. Solar-blind β-Ga2O3 NW PDs were also fabricated. Photo-responses of the fabricated PD were flat in the short-wavelength region while sharp cutoff occurred at 255 nm. With an incident light wavelength of 255 nm and an applied bias of 10 V, it was found that measured responsivity of the PD was 0.8 mA/W. It was also found that Noise equivalent power (NEP) and normalized detectivity (D*) were 7.63×10-10 W and 8.69×109 cmHz0.5W-1, respectively, when the voltage biased at 5 V. We also fabricate the GaN NWs PDs. To fabricate GaN NWs PDs, the β-Ga2O3 NWs were converted to GaN NWs through ammonification. Compared with conventional two-dimensional (2D) GaN PD, it was found that we could achieve a 1000 times larger photocurrent from the GaN NW PD. With an incident light wavelength of 360 nm and a 5 V applied bias, it was found that measured responsivities were 70.4 and 0.12 A/W for the GaN NW PD and the conventional 2D GaN PD, respectively. It was also found that dynamic response of the GaN NW PD was stable and reproducible with an on/off current contrast ratio of around 1000. Furthermore, UV-to-visible rejection ratio observed from the GaN NW PD was also larger, as compared to conventional 2D GaN PD.

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