Leakage current in quantum-cascade lasers through interface roughness scattering

Abstract

The impact of interface roughness (IFR)-scattering on the quantum efficiency of quantum-cascade lasers (QCLs) is demonstrated and analyzed both experimentally and theoretically. An InGaAs/InAlAs strain-compensated QCL emitting at λ ∼ 5.4 μm is analyzed in pulsed mode at liquid nitrogen temperatures. Measurements of the differential slope efficiency as a function of laser resonator length allow the pumping efficiency to be measured as a function of electron temperature. Excellent agreement is obtained when comparing the data to a calculation of the leakage current into higher-lying states via IFR-scattering, providing evidence of the importance of IFR-scattering on the QCLs quantum efficiency.

Room temperature negative differential resistance in terahertz quantum cascade laser structures

“…This may result in increased non-radiative scatterings between the lasing states and may promote carrier leakage into higher states. [13][14][15][16] However, in contrast to what is observed in this work, an earlier work on tall barrier THzQCLs shows slightly better laser performance for a device with pure AlAs injector barriers (in comparison to a 15% Al reference device), 5 suggesting a negligible negative contribution of the interface roughness scattering to the device's performance. Clearly, the effects of interface roughness scattering on the performance of high barriers THz-QCLs still need further investigations.…”

“…As a result, the dynamic range of device VB0743 is significantly reduced, so is T max . An additional effect that may contribute to the reduced performance of high-barrier devices, including the ones of this work, may be the interface roughness scattering [13][14][15][16] which scales up with the increase of the barriers' height. This may result in increased non-radiative scatterings between the lasing states and may promote carrier leakage into higher states.…”

Influence of interface roughness in quantum cascade lasers

“…The two main causes of elastic scattering in QCLs are impurities, where electrons are scattered by the dopant ions, and interface roughness (IFR), which provides scattering due to imperfections of the interfaces between two semiconductor layers. The interface roughness scattering 7,8 is dominant in mid-IR QCLs, 9 and is also relevant in THz QCLs. 10 It affects the occupation of states by scattering electrons from one mini-band into another, due to the lack of lateral symmetry at the interfaces.…”

High-Power Mid-Infrared (λ∼3-6 μm) Quantum Cascade Lasers

“…1) ≥ 50 meV both LO-phonon-and IFRscatering triggered carrier leakage primarily occur thorough the ul +1 level. Then, it can be shown [6,16,17] that:…”