Carrier confinement engineering in InGaAs/AlGaAs MQWs via an asymmetric barrier

Abstract

The effect of an asymmetric potential barrier, engineered by selectively removing a GaAs interlayer at the downstream side of carrier diffusion in InGaAs/AlGaAs multiple quantum wells (MQWs), is investigated. The structures are grown by molecular beam epitaxy (MBE) and characterized by high-resolution X-ray diffraction (HRXRD) and photoluminescence (PL) spectroscopy. HRXRD analysis reveals that the asymmetric barrier enhances indium interdiffusion and increases the dislocation density. However, the PL results demonstrate a significant enhancement in the emission intensity for the asymmetric structure. This improvement is attributed to superior carrier confinement, achieved by the higher potential barrier on the downstream side, which effectively reduces carrier escape. It is concluded that the strategic formation of an asymmetric barrier via interlayer removal provides a viable approach for boosting the luminescence efficiency of MQWs, in which the gain from improved carrier confinement outweighs the detrimental effects of slightly degraded crystal quality.