Optimization of Molecular Beam Epitaxy (MBE) Growth for the Development of Mid-Infrared (IR) II–VI Quantum Cascade Lasers

Quantum cascade (QC) lasers operating in the mid-infrared (IR) are being intensely pursued for environmental sensing and other important technological applications. Having demonstrated mid-IR (3 μm to 5 μm) electroluminescence (EL) from a II–VI intersubband device based on wide-band-gap (2.9 eV) Zn0.24Cd0.26Mg0.5Se on InP, there has been a drive towards production of a QC laser from these materials. To achieve lasing, waveguiding layers that straddle the active region used in the EL structure must be included. Initial attempts to grow this more complex structure resulted in degradation of the material quality. This paper presents the optimization steps required for the growth of the full QC laser structure and discusses possible mechanisms for the degraded quality.