Spiral growth of InGaN/InGaN quantum wells due to Si doping in the barrierlayers

We have examined Si-doping effects in InGaN/InGaN quantum-well (QW) structu res, especially the influence of Si-doped InGaN barrier layers on the growt h mechanism of QW structures, by atomic force microscopy (AFM) and by photo luminescence (PL) and cathodoluminescence (CL) spectroscopy. Our AFM observ ations revealed that Si-doped InGaN barriers strongly affect the growth mod e of overlying InGaN QW layers. This effect leads to the formation of nanos cale islands (with a density of 10(8) cm(-2)) due to spiral growth of the Q W layers. The spirally grown nanoscale islands significantly increase the P L intensity. Through spatially resolved CL observations, we found that the number of dot-like CL bright spots increased dramatically when the barrier layers were Si doped, and the increased density of the spots was in good ag reement with the increased density of the nanoscale islands observed by AFM . By combining these results, we show that the spirally grown QW structures produced by Si doping of the barriers effectively reduce the fluctuation o f the band-gap potential in InGaN QW layers. (C) 1999 American Institute of Physics. [S0003-6951(99)01108-0].