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Title:The transistor-injected quantum cascade laser
Author(s):Chen, Kanuo
Director of Research:Dallesasse, John M.
Doctoral Committee Chair(s):Dallesasse, John M.
Doctoral Committee Member(s):Bayram, Can; Feng, Milton; Jin, Jianming
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Transistor-injected quantum cascade laser
Heterojunction bipolar transistor
Quantum cascade laser
Light-emitting transistor
Abstract:Since its invention in 1994 the quantum cascade laser has become the most important coherent emission source for mid-infrared and terahertz ranges. The quantum cascade laser is a unipolar semiconductor laser that utilizes electron transitions between quantized states in the conduction band for optical emission. Due to the unipolar nature of the device, the quantum cascade laser cannot deliver spectrally stable output under different levels of current injection, which limits its application in gas sensing spectroscopy, imaging and free space optical communication. The light-emitting transistor and the transistor laser are novel three-terminal photonic devices based on heterojunction bipolar transistors. In the direct-bandgap base of a light-emitting transistor the electron-hole recombination is utilized for optical emission. In a transistor laser the radiative recombination is further enhanced by inserting one or multiple quantum wells in the base region to achieve coherent emission. Both the light-emitting transistor and the transistor laser maintain the behavior of a heterojunction bipolar transistor while enabling optical emission from the base region, allowing both electrical and optical output at the same time. The transistor scheme also helps to achieve higher bandwidth and higher data transmission rate in both the light-emitting transistor and the transistor laser than in traditional semiconductor laser diodes, making them promising candidates for the next generation of optical interconnects. The transistor-injected quantum cascade laser is inspired by the three-terminal scheme of the transistor laser. The key feature of the transistor-injected quantum cascade laser is to incorporate the active region of a quantum cascade laser between the p-type base and the n-type collector of an n-p-n transistor. The transistor structure allows separate control of the current through the quantum cascade active region and the voltage drop across the region. This would enable stable spectral output from the electron intersubband transition and separation of current and voltage modulation. The inserted quantum cascade region in the base-collector junction also forms a tunable barrier for electrons to transition from the base into the collector which controls the radiative base recombination. As the quantum states in the incorporated cascade region align to create decent spatial overlap for designed intersubband emission, the impedance to electrons flowing out of the base is reduced and so is the recombination lifetime. When the quantum states are off-aligned the impedance to electrons escaping the base is enhanced and so is the radiative base recombination. The modulation of the base recombination through the alignment of the quantum states is a unique and interesting feature of the transistor-injected quantum cascade laser which also promises more applications for the device.
Issue Date:2017-11-29
Rights Information:Copyright 2017 Kanuo Chen
Date Available in IDEALS:2018-03-13
Date Deposited:2017-12

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