Evidence of Intersubband Linewidth Narrowing Using Growth Interruption Technique

Ngoc Tran,François Julien,Jean-Michel Manceau,Arnaud Jollivet,Alberto Bertocci,Giorgio Biasiol,Raffaele Colombelli

doi:10.3390/photonics6020038

Abstract

We report on the systematic study of two main scattering mechanisms on intersubband transitions, namely ionized impurity scattering and interface roughness scattering. The former mechanism has been investigated as a function of the dopants position within a multiple GaAs/AlGaAs quantum well structure and compared to the transition of an undoped sample. The study on the latter scattering mechanism has been conducted using the growth interruption technique. We report an improvement of the intersubband (ISB) transition linewidth up to 11% by interrupting growth at GaAs-on-AlGaAs interfaces. As a result, the lifetime of intersubband polaritons could be improved up to 9%. This leads to a reduction of 17% of the theoretical threshold intensity for polaritonic coherent emission. This work brings a useful contribution towards the realization of polariton-based devices.

Highlights

Intersubband transitions (ISBT) in square semiconductor quantum wells (QW) are the building blocks of mid-infrared/terahertz optoelectronic devices, such as quantum cascade lasers (QCL) [1], quantum well infrared photodetectors (QWIP) [2], second harmonic generation [3], and potential polaritonic coherent emitters [4,5]
As we demonstrated the effect of the growth interruption on the ISB linewidth narrowing, we investigated the nature of the broadening induced by interface roughness
We have explored the two main scattering mechanisms causing the broadening of ISBT transition

Summary

Introduction

Intersubband transitions (ISBT) in square semiconductor quantum wells (QW) are the building blocks of mid-infrared/terahertz optoelectronic devices, such as quantum cascade lasers (QCL) [1], quantum well infrared photodetectors (QWIP) [2], second harmonic generation [3], and potential polaritonic coherent emitters [4,5]. Among the various relaxation mechanisms of electrons in confined electronic states, experiments suggest that elastic processes, such as interface roughness and ionized impurities, are the major axes of improvement to reach the intrinsic linewidth limitation due to phonons [6,7,8]. Prior to the tremendous success of the QCL, the improvement of ISBT lifetime was an active field of research. Its interest has decreased, it remains of importance especially in the perspective of intersubband polaritonic lasers [5]. Such polaritonic coherent emitter is based on final state stimulation, and it was proposed to exploit longitudinal optical (LO) phonon-polariton interaction as the main spontaneous scattering mechanism

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Conclusion