Abstract
The effect of the quantum dot (QD) deposition temperature is discussed for dot-in-a-well (DWELL) structures with a view to their optimization for broadband applications. Atomic force microscopy (AFM) analysis allows the measurement of the quantum dot and the defective island density. The reduced QD growth temperature results in broad emission spectrum and increased defective island density. Reduced electroluminescence efficiency, higher reverse leakage currents, and lower reverse breakdown voltage could be correlated to the presence of the defective island density. Maximal output power is obtained for devices with a QD growth temperature of 500 degrees C, whilst the preferred spectral shape and QD density is obtained at the lowest temperature, 470 degrees C. To benefit from broad emission bandwidth, the growth conditions need to be further optimized to avoid, or at least reduce, the defective island density. (C) 2012 The Japan Society of Applied Physics