Temperature performance of terahertz quantum-cascade lasers: experiment versus simulation

Li, He Ping; Cao, Jiafeng; Tan, Zhongxin; Han, Yanling; Guo, Xiaoyang; Feng, Shipeng; Luo, Hongzhi; Laframboise, S. R.; Liu, H C

doi:10.1088/0022-3727/42/2/025101

Cited by 11 publications

(8 citation statements)

References 16 publications

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“…Combining versatility and reliability with relative computational efficiency, the EMC approach has been widely used for the analysis, design and optimization of QCLs. 46,47,[99][100][101][102][103][104][105][106][107][108][109][110] In both the rate equation and EMC approach, the carrier transport is described by scattering-induced transitions of discrete electrons between the quantized energy levels, corresponding to a hopping transport model. Such methods are referred to as semiclassical, since the energy quantization in the QCL heterostructure is considered, but quantum coherence effects and quantum mechanical dephasing are not included.…”

Section: Overview and Classification Of Carrier Transport Modelsmentioning

confidence: 99%

Modeling techniques for quantum cascade lasers

Jirauschek

Kubis

2014

Applied Physics Reviews

227

178

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Quantum cascade lasers are unipolar semiconductor lasers covering a wide range of the infrared and terahertz spectrum. Lasing action is achieved by using optical intersubband transitions between quantized states in specifically designed multiple-quantum-well heterostructures. A systematic improvement of quantum cascade lasers with respect to operating temperature, efficiency and spectral range requires detailed modeling of the underlying physical processes in these structures. Moreover, the quantum cascade laser constitutes a versatile model device for the development and improvement of simulation techniques in nano- and optoelectronics. This review provides a comprehensive survey and discussion of the modeling techniques used for the simulation of quantum cascade lasers. The main focus is on the modeling of carrier transport in the nanostructured gain medium, while the simulation of the optical cavity is covered at a more basic level. Specifically, the transfer matrix and finite difference methods for solving the one-dimensional Schr\"odinger equation and Schr\"odinger-Poisson system are discussed, providing the quantized states in the multiple-quantum-well active region. The modeling of the optical cavity is covered with a focus on basic waveguide resonator structures. Furthermore, various carrier transport simulation methods are discussed, ranging from basic empirical approaches to advanced self-consistent techniques. The methods include empirical rate equation and related Maxwell-Bloch equation approaches, self-consistent rate equation and ensemble Monte Carlo methods, as well as quantum transport approaches, in particular the density matrix and non-equilibrium Green's function (NEGF) formalism. The derived scattering rates and self-energies are generally valid for n-type devices based on one-dimensional quantum confinement, such as quantum well structures

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Section: Overview and Classification Of Carrier Transport Modelsmentioning

confidence: 99%

Modeling techniques for quantum cascade lasers

Jirauschek

Kubis

2014

Applied Physics Reviews

227

178

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“…In the last decade, significant scientific effort has been directed towards identifying the main temperaturedegrading mechanisms [5][6][7][8] , as well as finding optimized QCL designs [9][10][11][12][13][14] . The degrading mechanisms include thermal backfilling 3,15 , thermally activated LO phonon emission [6][7][8]16 , increased broadening [17][18][19] , and carrier leakage into continuum states 20 . When numerically optimizing a design, it is important to take all of these effects into consideration, in order to ensure a close correspondence between the model and the real device.…”

mentioning

confidence: 99%

Two-well quantum cascade laser optimization by non-equilibrium Green's function modelling

Franckié

Bosco

Beck

et al. 2018

Applied Physics Letters

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We present a two-quantum well THz intersubband laser operating up to 192 K. The structure has been optimized with a non-equilibrium Green's function model. The result of this optimization was confirmed experimentally by growing, processing and measuring a number of proposed designs. At high temperature (T > 200 K), the simulations indicate that lasing fails due to a combination of electron-electron scattering, thermal backfilling, and, most importantly, re-absorption coming from broadened states.Terahertz quantum cascade lasers (QCLs) 1 are interesting candidates for a wide variety of potential applications 2,3 . However, to date, their operation is limited to ∼200 K 4 and the necessity of cryogenic cooling hinders a widespread use of these devices. In the last decade, significant scientific effort has been directed towards identifying the main temperaturedegrading mechanisms 5-8 , as well as finding optimized QCL designs 9-14 . The degrading mechanisms include thermal backfilling 3,15 , thermally activated LO phonon emission [6][7][8]16 , increased broadening [17][18][19] , and carrier leakage into continuum states 20 . When numerically optimizing a design, it is important to take all of these effects into consideration, in order to ensure a close correspondence between the model and the real device. Combined with the fact that the optimization parameters are typically trade-offs for one another, the task is very complex. Here, typically simpler rate equation or density matrix models are used in order to more quickly sweep the parameter space 21-23 , while more advanced models, such as non-equilibrium Green's functions (NEGF) or Monte-Carlo, are used to validate and analyze the final designs 13,[24][25][26] . In contrast, in this work we will employ an advanced model directly at the optimization stage. Specifically, we shall use a NEGF model 27 , capable of accurately simulating experimental devices 13,26,28 and including the most general treatment of scattering, from all relevant processes.The goal of the optimization is to achieve the highest possible operating temperature. Thus, the gain of the active medium should be maximized at high lattice temperature, and simultaneously the external losses minimized. The key figures for gain are inversion, oscillator strength, and line width 29 . These are mainly controlled by the doping density, the energy difference E ex between the lower laser level ll and the extractor state e, and the width of the two barriers: the laser and injection barriers. Population inversion increases with doping, although a too high level promotes detrimental effects, such as electron-electron scattering. E ex , which is chosen to be close to the LO phonon resonance E LO in order to have a short ll lifetime, and the laser frequency ω are mainly determined by the well widths. The laser barrier width determines the oscillator strength, which at the same time affects inversion; a more vertical transition

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“…We would like to note that, as Li et al (2009b) demonstrated, the calculations of gain peak require to account for changes of Dm with temperature. Only when Dm broadening with increase of temperature had been included, the agreement with experimental results has been achieved.…”

Section: Optical Gainmentioning

confidence: 94%

“…Temperature performance and limiting factors for high temperature operation of various designs of THz QCL have been addressed in multiple reports (Jirauschek and Lugli 2008a, b;Li et al 2009b;Mátyás et al 2010a;Cao 2010, 2012).…”

Section: Examples Of MC Studies Of Qclmentioning

confidence: 99%

Monte Carlo modeling applied to studies of quantum cascade lasers

2017

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One of the commonly used approaches of solving electron transport problems in quantum cascade lasers (QCL) is the Monte Carlo (MC) method, based on semiclassical description in the framework of the Boltzmann Transport Equation. A major benefit of MC modeling is that it only relies on well-established material parameters and structure specification, in most cases without the need to use phenomenological parameters. The results of the modeling can be easily interpreted and they give microscopic insight of QCL operation. The goal of the present paper is to review the application of the MC technique to the studies of operation of QCL. The description of the components of the simulation algorithm is provided. Various physical mechanisms governing electron transport in QCL are described and their influence on the operation are reviewed.

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Temperature performance of terahertz quantum-cascade lasers: experiment versus simulation

Cited by 11 publications

References 16 publications

Modeling techniques for quantum cascade lasers

Modeling techniques for quantum cascade lasers

Two-well quantum cascade laser optimization by non-equilibrium Green's function modelling

Monte Carlo modeling applied to studies of quantum cascade lasers

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