Interplay of GaAsP barrier and strain compensation in InGaAs quantum well at near-critical thickness

The effect of GaAs_1-yP_y tensile-strained barriers on suppressing the partial strain relaxation of InGaAs/GaAs multiple quantum wells (MQWs) is investigated when the thickness of a heavily strained In_xGa_1-xAs QW is near-critical thickness. The strain relaxations of In_0.4Ga_0.6As MQWs with and without strain-compensating GaAs_1-yP_y barriers are characterized using X-ray diffraction reciprocal space mapping (RSM) and micro-photoluminescence (μ-PL) mapping. A significant amount of strain relaxation (~1.53%) is measured when the thickness of each In_0.4Ga_0.6As QW within a 4-period MQW becomes 9.5 nm in the absence of strain-compensating layers. By adding two ~5 nm GaAs_0.67P_0.33 tensile-strained barriers sandwiching each QW, the strain relaxation in the In_0.4Ga_0.6As/GaAs_0.67P_0.33/GaAs MQWs is reduced to ~0.3% together with decreased surface roughness. Our study shows that tensile barriers with proper elastic energy densities are essential to achieve efficient strain compensation in a heavily-strained InGaAs MQW structure, which provides an important insight into the understanding of how to better achieve the benefits of strain compensation in III-V based QWs and superlattices.