Impact of Interface Roughness Scattering on the Performance of GaAs/AlxGa1-xAs Terahertz Quantum Cascade Lasers

Yuri V. Flores, Asaf Albo

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

We investigate the impact of interface roughness (IFR) scattering on the performance of a series of the state-of-the-art GaAs/AlxGa1-xAs terahertz quantum cascade lasers (THz-QCLs) through a calculation of the induced inhomogeneous broadening and intersubband scattering rates. Our analysis includes two GaAs/Al0.15Ga0.85As THz-QCL devices with measured maximum operating temperatures at Tmax = 177 K and 175 K, two GaAs/Al0.30Ga0.70As devices with Tmax = 150 K and 89 K, a GaAs/AlAs-Al0.15Ga0.85As device with Tmax = 18$ K, and a GaAs/AlAs device that did not lase. The investigated QCL wafers were grown at the same solid-source molecular beam epitaxy facility and at fixed parameters, so that we expect a constant interface roughness quality for all devices. We find negligible impact of IFR scattering on the performance of devices that use x = 0.15 barriers as well as for devices that use x = 0.30 barriers with wide > 40 monolayers (ML) wells to support upper and lower laser levels. Fixing the barrier height to x =0.30 , we calculate a drastic increase of the IFR-induced linewidth broadening from ~0.66 meV to ~2 meV when the quantum wells thicknesses reduce from ~40 ML to ~30 ML and relate this effect to the observed reduction of Tmax from 150 to 89 K. Furthermore, we calculate a large (~2 meV) IFR linewidth broadening and short (~1 ps) IFR intersubband scattering times for the device with pure AlAs layers and relate the consequent reduction of optical gain to the nonlasing of this device.

Original languageEnglish
Article number7890460
JournalIEEE Journal of Quantum Electronics
Volume53
Issue number3
DOIs
StatePublished - Jun 2017
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 1965-2012 IEEE.

Keywords

  • Interface roughness
  • intersubband transitions
  • quantum cascade laser
  • terahertz emission

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