應用發光電晶體開發之光電反及閘SR閂鎖器與數據多工器

Abstract

發光電晶體(Light emitting transistor, LET)為一新穎的三端元件，因為其特殊的光電雙輸出特性，可同時作為光發射器、光調變器以及光接收器來使用，且其自發性復合載子生命週期為皮秒等級，可以進行快速的調變，故發光電晶體於光電整合(Opto-Electronics Integrated Circuits, OEICs)領域中具有相當的優勢。 本論文第一部分中將先介紹兩種不同訊號輸入方式的光電邏輯閘，並比較其輸出訊號之延遲情況，以及使用異質接面光電晶體(Heterojunction phototransistor, HPT)和光二極體(Photodiode, PD)做為光偵測器的輸出狀態差異，並提出使用外接電阻來改善電路輸出速度的想法，進而發現輸出訊號之波形穩定性與輸出速度會互相牽制。 第二個部分中，基於單一光電邏輯閘電路的量測結果，我們將兩個反及閘(NAND)中發光電晶體之基極與集極相互連接，形成SR閂鎖器(Latch)電路，來說明發光電晶體邏輯電路之訊號「儲存」特性，並在SR閂鎖器電路中加入時序訊號(Clock)以形成SR正反器(Flip-Flop)電路，透過調整時序訊號可以將輸出訊號控制在一段時間之中，而非整個時間軸。 最後一個部分，將繼續延伸發光電晶體的應用範圍，設計出發光電晶體數據多工器，來證明發光電晶體邏輯電路之「選擇」特性，透過電路中之選擇訊號，可以在兩個輸入訊號中選擇一個作為輸出訊號，且輸入及輸出訊號皆為光訊號的形式，可以確實發揮發光電晶體在光電整合領域之優勢，此為學界首次以發光電晶體整合電路製作出數據多工器之研究。

Light emitting transistor (LET) is a novel “three-port” device, which can simultaneously transmit both electrical and optical signals. It can be used as the light transmitter, light modulator, and photodetector in different situations. Additionally, owing to the picosecond level of recombination life time, the LET can be quickly modulated under high frequencies. These characteristics mentioned above make the LET suitable as a building block for optoelectronic logic gate circuits. In the first part of this thesis, we will introduce two types of optoelectronic logic gates with different input methods and compare the propagation delay of their output signals. Then we analyze the measurement results when using the heterojunction phototransistor (HPT) and the photodiode (PD) as the photodetector. After coming out of the idea of using external resistors to improve the output speed of the circuit, it was found that the waveform stability and the output speed would be a compromise. As for the second part, we combine two optoelectronics NAND gates together by connecting the base and the collector of them and form the SR latch circuit. This successfully proves that the logic gate circuit based on the LET has the signal “storing” function. By adding a “CLK(clock)” signal into the SR latch circuit, a SR flip-flop circuit can be demonstrated. The output signals can be controlled in a short period of time, rather than of the entire time axis. In the last part, we continue to expand on the applications of the LET by designing the circuit of the multiplexer. It shows that the logic gate circuit composed of the LETs has the function of “selecting” output signal. We can change the select input signal to choose one of the two input signals to be the output signal. And because the input and output signals are both in the form of optical signals, it can take advantage of the LET for its special dual transmission characteristics. This study is almost the first time fabricating a multiplexer based on the LET in academia.