Contrasting influence of charged impurities on transport and gain in terahertz quantum cascade lasers
Contrasting influence of charged impurities on transport and gain in terahertz quantum cascade lasers
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DOI：
10.1103/physrevb.92.241306
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发表时间：
2015-12-29
影响因子：
3.7
通讯作者：
Grange, Thomas
中科院分区：
文献类型：
--
作者：
Grange, Thomas
利用非平衡绿色函数计算了共振声子太赫兹量子级联激光器的输运和增益特性。杂质散射被证明是负责对比在运输和增益特性的非线性效应。对于典型的掺杂浓度，电流密度被发现是弱敏感的杂质散射强度。与此相反，计算的增益被发现是非常敏感的杂质散射强度。这种差异归因于带电杂质的长程耦合的强动量依赖性。小动量杂质散射被证明是负责共振隧穿过程的非相干制度。这些对杂质散射的关键作用的见解开辟了一条通过设计掺杂分布来改进太赫兹量子级联激光器的途径。
Transport and gain properties of a resonant-phonon terahertz quantum cascade laser are calculated using nonequilibrium Green's functions. Impurity scattering is shown to be responsible for contrasting nonlinear effects in the transport and the gain properties. For typical doping concentrations, the current density is found to be weakly sensitive to the impurity scattering strength. In contrast, the calculated gain is found to be very sensitive to the impurity scattering strength. This difference is attributed to the strong momentum dependence of the long-range coupling to charged impurities. Small-momentum impurity scattering is shown to be responsible for an incoherent regime of resonant tunneling processes. These insights into the crucial role of impurity scattering open a route of improvement of terahertz quantum cascade lasers by engineering of the doping profile.