Active region design of a terahertz GaN/Al0.15Ga0.85N quantum cascade laser

We propose the idea of developing THz quantum cascade lasers (QCLs) with GaN-based quantum well (QW) structures with significant advantages over the currently demonstrated THz lasers in the GaAs-based material system. While the ultrafast longitudinal optical (LO) phonon scattering in AlGaN/GaN QWs can be used for the rapid depopulation of the lower laser state, the large LO-phonon energy (similar to90 meV) can effectively reduce the thermal population of the lasing states at higher temperatures. Our analysis of one particular structure has shown that a relatively low threshold current density of 832 A/cm(2) can provide a threshold optical gain of 50/cm, at room temperature. We have also found that the characteristic temperature in this structure is as high as 136 K. (C) 2004 Elsevier Ltd. All rights reserved.