Characterization of Heterojunction Bipolar Phototransistor with Integrated Two-Section Light-Emitting Transistors and Logic Gate Application
Date Issued
2015
Date
2015
Author(s)
Hsu, Yuan-Fu
Abstract
In an era of information explosion, combining optical and electrical signals into a single chip to form OptoElectronic Integrated Circuits (OEICs) is one of the most important researches and developments in the future. In 2004, Milton Feng and Nick Holonyak, Jr. invented the first light-emitting transistor (LET) in UIUC. The III-V LETs with a direct bandgap and carrier injection have made themselves as three-port (an electrical input, an electrical output and a “third-port” optical output) devices. The LETs has a similar epitaxial structure to the conventional heterojunction bipolar transistor (HBT). The base, collector and subcollector layer of the LET can be employed to form a p-i-n diode for photon detection, which works as a heterojunction phototransistor (HPT). Therefore, the LET has the unique characteristics to function like a photon transmitter and receiver, which has the potential to become a building block for next-generation OEICs. In this thesis, we demonstrate an integrated two-section light-emitting transistor with one section working as a light emitter and the other one working as a phototransistor. Firstly, we use this two-section device to characterize the HPT with different operation points (IB and VCE) and injected optical power. The responsivity of the HPT is 711.4 A/W. A tunnel junction is then incorporated to form a tunnel junction heterojunction phototransistor (TJ-HPT). With the help of the tunnel junction, the responsivity can be enhanced to 3404.8 A/W. Secondly, we characterize the microwave performance of the LET under different optical injections. Through the analysis of small-signal equivalent circuit models, we can analyze the transist time by deembedding the circuit paracistics effect. The cut-off frequency enhances from 1.4 GHz to 1.51 GHz under an optical power injection. Thirdly, we design and demonstrate the optical logic gates in the form of an AND gate and OR gate utilizing the characteristics of phototransistors. The AND gate and OR gate have a significant on/off ratio with injecting optical power. In the future, we can enhance the performance of the two-section device by substituting theLET with the transistor laser (TL). Also we can design an optical NAND gate and NOR gate for future application of OEIC design.
Subjects
light-emitting transistor
heterojunction phototransistor
responsivity
cut-off frequency
logic gate
OptoElectronic Integrated Circuits
Type
thesis
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