Fabrication and Characterization of Heterojunction Bipolar Phototransistors for Opto-electrical Integrated Circuits
Date Issued
2014
Date
2014
Author(s)
Cheng, Gong-Sheng
Abstract
The heterojunction bipolar transistor (HBT) can be modified and operated as a three-port light-emitting device (an electrical input, an electrical output, and a third port optical output) by incorporating one or more quantum wells in the base region, thus becoming a heterojunction bipolar light-emitting transistor (LET). The epitaxy structure of the LET is very similar to the HBT so that we can operate the LET like a heterojunction phototransistor (HPT). The base, collector and sub-collector layers of a LET are designed to implement the p-i-n photodiode. The LET have the transiever and receiver characteristics, which becomes one of the best candidate of next generation OptoElectric Integrated Circuits (OEIC).
In this thesis, we have designd and fabricated the monolithic intergrated light-emitting transistor and heterojunction phototransistor utilizing the optical output and receiver charactrics of the LET. Typcial p-i-n mode current-voltage characteristics have been measured for an HPT with the optical input from the LET. The responsivity of p-i-n photodiode is about 0.1~0.23 A/W, but when operating the HPT at transistor mode the responsivity can be improved to 1.3 A/W. The HPT also can be measured with three-terminal configuration. We found that the current gain of HPT with three-terminal configuration has large improvement with small base current input (1 μA) from 1.35 to 12.3 due to the light absorption.
We can still improve the integration of the LET and HPT to enhance the performance. Firstly, we can fabricate wave guide between two devices to increase the coupling coefficient of two devices. Secondly, the LET can be substituted by the transistor laser (TL) due to the larger optical output. Finally, the area of optical window and the absorption litmit can be improved by the epitaxy of material and layout design.
Subjects
光電積體整合
發光電晶體
光電晶體
光響應度
Type
thesis
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