Short-period scattering-assisted terahertz quantum cascade lasers operating at high temperatures

Wang, Li; Lin, Tsung‐Tse; Wang, Ke; Grange, Thomas; Birner, Stefan; Hasegawa, Hideki

doi:10.1038/s41598-019-45957-8

Cited by 14 publications

(9 citation statements)

References 35 publications

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“…When increasing the doping concentration, it is essential to maximize population inversion in the active region, avoiding possible leakages, especially via high‐energy levels. This leakage can affect a reduction of 30% of the optical gain at high temperature [ 17 ] due to the thermal activation of multiple leakage types via high‐energy levels including horizontal‐direction leakage, shunt‐type leakage, and leakage to the continuum. The main benefit of varying barrier and well heights can introduce more design freedom for tuning the high‐energy levels and controlling the interaction between them and the basic ideal operation energy levels (injection, emission, and extraction levels).…”

Section: Methods and Discussionmentioning

confidence: 99%

“…Recently, leakage current via high-energy confined levels has been recognized as having an important role. [16][17][18] It is important to engineer the leakage at heavy doping because the strong band bending effect largely affects the parasitic leakage via sequential resonant tunneling. [19] In this work, we balance the design parameters and realize a realignment of resonant tunneling states.…”

Section: Introductionmentioning

confidence: 99%

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Over One Watt Output Power Terahertz Quantum Cascade Lasers by Using High Doping Concentration and Variable Barrier‐Well Height

Lin

Wang

et al. 2022

Physica Rapid Research Ltrs

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A GaAs/AlGaAs‐based terahertz quantum cascade laser with a peak power of 1.31 W and average power of 52 mW is demonstrated. To realize a high output power, an effective way is to increase the electron density at the active region by using a high doping level. This work aims to optimize a design enabling to use a heavy doping level, by realigning the resonant tunneling which can be seriously degraded due to a band bending from this heavy local doping. With variable quantum well and barrier height, the design owns an improved parameter tuning freedoms, and a saturation of peak gain can be achieved at a relatively high doping concentration of 1.0 × 1017 cm−3, which is twice higher than the recently reported device. Nonequilibrium Green's function method including full carriers scattering effect is used to carry out the design optimization, mainly including the realignment of resonant tunneling and suppression of leakages via high‐energy confined levels. In the experiment, a 14 μm thick active layer for this design is grown and also large mesa size is developed. To ensure a quasi‐continuous wave (quasi‐CW) operation, the heat dissipation is also managed.

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Section: Methods and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Over One Watt Output Power Terahertz Quantum Cascade Lasers by Using High Doping Concentration and Variable Barrier‐Well Height

Lin

Wang

et al. 2022

Physica Rapid Research Ltrs

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“…The simulation of optical gain is performed using the nextnano. NEGF simulation tool, which is a powerful and widely used tool in THz QCL simulations [39][40][41][42][43]. In the NEGF simulation tool, acoustic and optical phonon Each period in Figure 1a,b is separated by a blue dashed line.…”

Section: Development Of the Q1w Designmentioning

confidence: 99%

“…The simulation of optical gain is performed using the nextnano. NEGF simulation tool, which is a powerful and widely used tool in THz QCL simulations [39][40][41][42][43]. In the NEGF simulation tool, acoustic and optical phonon scattering, impurity scattering, IFR scattering, and alloy disorder scattering are accurately simulated by considering the full dependence of the scattered in-plane momentum.…”

Section: Development Of the Q1w Designmentioning

confidence: 99%

Theoretical Study of Quasi One-Well Terahertz Quantum Cascade Laser

Wen

Ban

2022

Photonics

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Developing a high-temperature terahertz (THz) quantum cascade laser (QCL) has been one of the major challenges in the THz QCL field over recent decades. The maximum lasing temperature of THz QCLs has gradually been increased, arguably by shortening the length of repeating periods of the quantum structure in the device’s active region from 7 wells/14 layers to 2 wells/4 layers per period. The current highest operating temperature of 250 K was achieved in a two-well direct-phonon design. In this paper, we propose a potential and promising novel quantum design scheme named the quasi one-well (Q1W) design, in which each quantum cascade period consists of only three semiconductor layers. This design is the narrowest of all existing THz QCL structures to date. We explore a series of the Q1W designs using the non-equilibrium green function (NEGF) and rate-equation (RE) models. Both models show that the Q1W designs exhibit the potential to achieve sufficient optical gain with low-temperature sensitivity. Our simulation results suggest that this novel Q1W scheme may potentially lead to relatively less temperature-sensitive THz QCLs. The thickness of the Q1W scheme is less than 20 nm per period, which is the narrowest of the reported THz QCL schemes.

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“…Figure 10. Conduction band diagram and the tight-binding states of two-well SA design with three neighboring periods (n-1,n,n+1) (a); The voltage-current plots at high temperatures of 300 K when the different number of the highlying nonrelevant states are included for calculations(b);The current mapping resolved by the growth direction and the energy when the nonrelevant states are included(c), Ref [49]…”

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confidence: 99%

High-Temperature Operating Narrow-Period Terahertz Quantum Cascade Laser Designs

Wang¹,

Hasegawa²

2023

Light-Emitting Diodes - New Perspectives

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Presently, terahertz quantum cascade lasers still suffer from operations below room temperature, which prohibits extensive applications in terahertz spectra. The past continuous contributions to improving the operating temperatures were by clarifying the main thermal degradation process and proposing different designs with the optical gain demonstrating higher temperature cut-offs. Recent designs have attempted to employ a narrow period length with a simplified and clean state system, and reach renewed operating temperatures above 200 K. This study reveals how historic designs approach such narrow-period designs, discus the limitations within those designs, and show further possible designs for higher operating temperatures.

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Short-period scattering-assisted terahertz quantum cascade lasers operating at high temperatures

Cited by 14 publications

References 35 publications

Over One Watt Output Power Terahertz Quantum Cascade Lasers by Using High Doping Concentration and Variable Barrier‐Well Height

Over One Watt Output Power Terahertz Quantum Cascade Lasers by Using High Doping Concentration and Variable Barrier‐Well Height

Theoretical Study of Quasi One-Well Terahertz Quantum Cascade Laser

High-Temperature Operating Narrow-Period Terahertz Quantum Cascade Laser Designs

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