A modulated As molecular-beam epitaxy method is utilized to grow high-quality In0.48Al0.52As epilayer at a low substrate temperature, which is compatible to the optimal In0.47Ga0.53As growth condition. The reflection high-energy electron diffraction intensity oscillations recorded during modulated As beam epitaxy shows that a persistent layer-by-layer growth mode is maintained throughout the epitaxy process. The high electron mobility, high photoluminescence (PL) intensity, and narrow PL linewidth have confirmed the low defect generation/incorporation during the modulated As beam epitaxy of the In0.48Al0.52As. The effect of interface smoothing is confirmed by the extremely narrow 77 K PL linewidth of an In0.47Ga0.53As/In0.48Al0.52As quantum well stack heterostructure grown by this method.