Importance of growth direction in mid-infrared quantum cascade lasers

Bouzi, Pierre M.; Chiu, YenTing; Deutsch, C.; Dikmelik, Yamaç; Song, Yu; Tokranov, V.; Oktyabrsky, S.; Gmachl, Claire F.

doi:10.1063/1.4890311

Cited by 5 publications

(5 citation statements)

References 22 publications

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“…Recent results from direct interface roughness measurements of InGaAs/InAlAs heterojunctions grown by MOCVD show that InGaAs-on-InAlAs interfaces are rougher and more strongly correlated than InAlAs-on-InGaAs ones . Therefore, we expect also a favored operating direction with respect to the growth direction, as recently shown for symmetric InGaAs/InAlAs mid-infrared QCL structures …”

Section: Influence Of Growth-related Asymmetriessupporting

confidence: 69%

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High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers

et al. 2017

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We report on high-power terahertz quantum cascade lasers based on low effective electron mass InGaAs/InAlAs semiconductor heterostructures with excellent reproducibility. Growth-related asymmetries in the form of interface roughness and dopant migration play a crucial role in this material system. These bias polarity dependent phenomena are studied using a nominally symmetric active region resulting in a preferential electron transport in the growth direction. A structure based on a three-well optical phonon depletion scheme was optimized for this bias direction. Depending on the sheet doping density, the performance of this structure shows a trade-off between high maximum operating temperature and high output power. While the highest operating temperature of 155 K is observed for a moderate sheet doping density of 2 × 1010 cm–2, the highest peak output power of 151 mW is found for 7.3 × 1010 cm–2. Furthermore, by abutting a hyperhemispherical GaAs lens to a device with the highest doping level a record output power of 587 mW is achieved for double-metal waveguide structures.

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Section: Influence Of Growth-related Asymmetriessupporting

confidence: 69%

“…21 Therefore, we expect also a favored operating direction with respect to the growth direction, as recently shown for symmetric InGaAs/InAlAs mid-infrared QCL structures. 22 …”

Section: Influence Of Growth-related Asymmetriesmentioning

confidence: 99%

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers

et al. 2017

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“…We examine the influence of changes to the interface roughness on the gain spectrum and consider the limitations of the rate equation approach when evaluating spectra. Recent work has demonstrated a 15% difference in the width of electroluminescence spectra for mid-infrared QCLs operated under different polarity due to asymmetry in the interface roughness [28]. In this work, L was 6 nm and D was 0.2 and 0.1 nm for the rough and smooth interfaces, respectively.…”

Section: Gain Spectrummentioning

confidence: 69%

Importance of coherence in models of mid-infrared quantum cascade laser gain spectra

Cui

Harter

Dikmelik

et al. 2017

J. Opt.

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We present a three-level model based on a density matrix to examine the influence of coherence and dephasing on the gain spectrum of mid-infrared quantum cascade lasers. The model is used to examine a quantum cascade active region with multiple optical transitions. We show how coherence can explain the origin of additional peaks in the gain spectrum. We also analyze the spectra calculated using the three-level model with a rate equation formalism to demonstrate the importance of considering interface roughness and limitations of the rate equation formalism. Specifically, we present how interface roughness influences the broadening and oscillator strength that are recovered using a rate equation analysis. The results of this work are important when considering the design of active regions with multiple optical transitions and could lead to devices with improved performance.

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“…Studies on symmetric active regions revealed the importance of the position of the dopant atoms within the injector of QCL active regions . The nominally rectangular doping profile is actually smeared out along the growth direction.…”

Section: Growth Optimizationmentioning

confidence: 99%

Evaluation of Material Systems for THz Quantum Cascade Laser Active Regions

Detz

Andrews

Kainz

et al. 2018

Phys. Status Solidi A

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Quantum cascade lasers (QCLs) have been realized in several different material systems. In the mid-infrared, active regions are predominantly based on In 0.53 Ga 0.47 As and InAs as quantum well material. Market-ready devices routinely provide continuous-wave operation at room temperature. For their THz counterparts, the situation is less clear. The most common material system for THz QCLs is the inherently lattice-matched combination of GaAs with Al 0.15 Ga 0.85 As barriers. Yet, these devices still only reach a maximum operating temperature of 200 K with a lack of progress within the past years. Based on the identification of key parameters, this work reviews material systems for quantum cascade lasers with an emphasis on material and growth-related aspects and the goal to identify promising candidates for future device generations. Similar active regions realized in different material systems allow to estimate the gain per unit thickness, as well as total growth times and relative thickness errors.

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Importance of growth direction in mid-infrared quantum cascade lasers

Cited by 5 publications

References 22 publications

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers

Importance of coherence in models of mid-infrared quantum cascade laser gain spectra

Evaluation of Material Systems for THz Quantum Cascade Laser Active Regions

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