在本論文中，主要研究以砷化鎵為基底的光電元件，可以分成三個部分，第一是製作異質接面發光電晶體 (HBLET)，第二是製作位置測定感測器 (PSD)，第三是製作三層接面太陽能電池 (Multijunction solar cell)，並探討其元件的特性和提出不同的分析方法所得到的結果。首先，針對異質接面發光電晶體的部分，我們已經成功完成兩種鈍化的製程，透過穩定的製程用在一般異質接面電晶體 (HBT)上，而得到在VBE = 1.35 V可以得到電流增益接近62，但是同樣的製程用在異質接面發光電晶體上，其電流增益都小於1，因為在射極注入電子當在通過基極時大部分的電子都會被電洞復合，進而產生光和熱的形式散失，使得電流增益都小於1，而我們也得到異質接面發光電晶體的光特性上有良好的表現，其在基極電流110mA下，可以得到光功率1.09 mW。對於異質接面發光電晶體不僅可以獲得光訊號也可以透過基極去調變光的強度，但是光電訊號是互相影響，所以如果要獲得較佳的電特性可以透過改變元件尺寸，也會有明顯的改善其元件特性。
第二個部分是探討三端點的位置測定感測器(3T-PSD)，主要希望可以得到元件的模型進而跟HBT積體化，從實驗的結果來看目前已經得到元件，在不同的光源下量測水平電壓差是和垂直電壓差是十分接近，也符合理論，在紅光波長638nm照射下其靈敏度大約為14.3 mV/mm，其結果十分線性計算其非線性度範圍0.3 ~ 1.3%。再透過實驗設計得到整體模型，一方面也可以經由量測得到不同方向電流和電流大小。而更明確的將元件整體的模型描繪出來，一部分我們也去分析其元件在不同的光源下量測其反應時間，目前得到的反應時間平均大約都在60 μs到 134 μs之間。
第三個部分是多層接面太陽能電池，我們針對多層接面太陽能電池做詳細的探討，我們都知道要完全吸收太陽光需要更寬的吸收頻譜，在半導體裡那就需要不同能隙的半導體，透過串聯的方式得到更好的轉換效率，但是我們通常注意到疊加多層材料可以增加開路電壓，而忽略掉短路電流。我們透過兩種方法，一種是透過製程的方式，透過量測分析得到各層光電流，但是利用製程的方法有一個最大困難點就是如果是中間那層吸收層的光電流最小時，你就沒辦法完整得知各層光電流的情況，所以第二方法就是為了解決這個困難而提出的方法，這個方法並不用透過製程的方式，只需要幾種波長的光源，透過調變不同強度的光源，可以推測其各層的光電流情況，能夠更有效率得到其多層接面太陽能電池的優劣。

In this dissertation, we focus on the GaAs-based optical devices. It can be mainly divided into three parts. First of all, we have successfully fabricated and investigated the device performance in the heterojunction bipolar light-emitting transistor (HBLET). Second, we report the GaAs p-i-n structure, which is layer-compatible to the base-collector junction of a conventional InGaP-GaAs heterojunction bipolar transistor (HBT), is utilized in the fabrication of a PSD. Third, the multijunction solar cell consisting of III-V materials of InGaP/InGaAs/Ge has been investigated.
At first, the common-emitter characteristics of the conventional HBT and HBLET are demonstrated. The peak value of common-emitter current gain β of the InGaP/GaAs HBT is close to 62 at 300K. On the other hand, the current gain of HBLET is in the range of 0.45-0.70, which is much smaller than that of HBT in the range of 30-65. For HBLET, the decrease of current gain is a trade-off to enhance light output power. The light output power increases linearly and achieves 0.58 mW at 50 mA and 1.09 mW at 110 mA. Due to the current applied to the base can modulate the light output power for HBLET; the current gain of HBLET is smaller than the conventional HBT.
Second part, the GaAs-based p-i-n position sensitive detector are fabricated by conventional processes including photolithography, vacuum evaporation, and wet etching technique and investigated the device characteristic. It is possible that integrating a PSD with an HBT amplifier to design PSD circuits. In particular, sensitivity and linearity are two of most important sensing properties. Static sensing properties of the three-terminal PSD operated in lateral photovoltaic mode are performed using a light intensity of 3 mW and red light spot (the wavelength of 638 nm) to show a sensitivity of 14.3 mV/mm. Nonlinearities obtained from the present PSD are as small as 0.31.3% for 638 nm light sources. According to the model of photodiodes, the assumption that the total photocurrent produce two different directions photocurrent to catch in the PSD and interdiction of the 638 nm red light with an incident power of 2 mW. They are static characteristics of the fabricated PSD operated in lateral photovoltaic mode and transvere photovoltaic mode as well as response times.
At last, the multijunction solar cells are formed by serially connecting multiple p-n junctions according to their energy-band gaps. Therefore the overall open-circuit voltage of the multijunction solar cell is equal to sum of individual open-circuit voltage associated with each subcell. However, the overall short-circuit current is limited by that of the subcell whose short-circuit is minimal. Our measurement system sets up for the nondestructive inspection of subcell’s short current. Destructive (using etching processes) and nondestructive inspection (using optical measurement) of subcell’s short circuit current were also discussed
 

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