The effect of growth interruption on the surface roughness of high indium content InGaAs layer growth by molecular beam epitaxy (MBE) is studied. In order to smooth the interface, either one monolayer of GaAs or one monolayer of AlAs are deposited, followed by growth interruption at both sides of the InGaAs layers. The photoluminescence (PL) demonstrates a significantly improved interface quality for high indium content InGaAs quantum well (QW) when smoothed by one monolayer GaAs deposition, followed by 15 s growth interruption compared to those grown without smoothing or with AlAs monolayer deposition and interruption. The optimized smoothing is obtained for a growth interruption time between 15 and 30 s at a growth temperature of 490 degrees C. Clear improvement of interface smoothness, continuity, and reduced structural defect density at the interface between high indium content QW and the GaAs barrier is observed by cross-sectional high resolution transmission electron microscopy (XHRTEM).