Compositional dependence of the bowing parameter for highly strained InGaAs/GaAs quantum wells

Abstract

Highly strained InGaAs/GaAs quantum wells (QWs) are studied using the complementary spectroscopic and high-resolution x-ray diffraction (HRXRD) techniques. It is found that the QW features can be precisely identified by solving the Schr\"odinger equation for a rectangular shape QW, thus ignoring any indium segregation effect and considering only the compositional dependence of bowing parameter (C) while using the QW parameters obtained from HRXRD measurements. The compositional dependence of ``C'' for ${\text{In}}_{x}{\text{Ga}}_{1\ensuremath{-}x}\text{As}$ QWs $(0.294\ensuremath{\le}x\ensuremath{\le}0.42)$ can be given by a linear relationship of $\text{C}=0.3525+0.9028x$, which provides a conduction band offset $(\ensuremath{\Delta}{\text{E}}_{\text{c}})$ of the functional form: $\ensuremath{\Delta}{\text{E}}_{\text{c}}=0.7529x+0.2917{x}^{2}\ensuremath{-}0.4785{x}^{3}$ using the band offset $({\text{Q}}_{\text{c}})$ value of 0.53. It is also observed that ${\text{Q}}_{\text{c}}$ is independent of the composition of QWs. Though the QW sample with the maximum strain showed some relaxation $(\text{R}\ensuremath{\approx}3.4%)$ as measured by the reciprocal space mapping in HRXRD, still it is largely insignificant and does not affect the measured value of ``C'' for the present set of QW samples.