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Open AccessArticle

Short Barriers for Lowering Current-Density in Terahertz Quantum Cascade Lasers

1
Department of Electrical and Computer Engineering, Lehigh University, Bethlehem, PA 18015, USA
2
Center for Integrated Nanotechnologies, Sandia National Laboratories, MS 1303, Albuquerque, NM 87185-1303, USA
*
Author to whom correspondence should be addressed.
Photonics 2020, 7(1), 7; https://doi.org/10.3390/photonics7010007
Received: 3 December 2019 / Revised: 23 December 2019 / Accepted: 2 January 2020 / Published: 8 January 2020
Scattering due to interface-roughness (IR) and longitudinal-optical (LO) phonons are primary transport mechanisms in terahertz quantum-cascade lasers (QCLs). By choosing GaAs/Al0.10Ga0.90As heterostructures with short-barriers, the effect of IR scattering is mitigated, leading to low operating current-densities. A series of resonant-phonon terahertz QCLs developed over time, achieving some of the lowest threshold and peak current-densities among published terahertz QCLs with maximum operating temperatures above 100 K. The best result is obtained for a three-well 3.1 THz QCL with threshold and peak current-densities of 134 A/cm2 and 208 A/cm2 respectively at 53 K, and a maximum lasing temperature of 135 K. Another three-well QCL designed for broadband bidirectional operation achieved lasing in a combined frequency range of 3.1–3.7 THz operating under both positive and negative polarities, with an operating current-density range of 167–322 A/cm2 at 53 K and maximum lasing temperature of 141 K or 121 K depending on the polarity of the applied bias. By showing results from QCLs developed over a period of time, here we show conclusively that short-barrier terahertz QCLs are effective in achieving low current-density operation at the cost of a reduction in peak temperature performance. View Full-Text
Keywords: terahertz lasers; quantum cascade lasers; interface roughness scattering; LO-phonon scattering terahertz lasers; quantum cascade lasers; interface roughness scattering; LO-phonon scattering
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Gao, L.; Reno, J.L.; Kumar, S. Short Barriers for Lowering Current-Density in Terahertz Quantum Cascade Lasers. Photonics 2020, 7, 7.

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