InAs/GaAs self-assembled quantum dots grown by ALMBE and MBE

We have studied the effect of different growth schemes of structures with InAs/GaAs self-assembled dots on the size of dots and, then, on their PL features. Lower confining layers, dots and upper confining layers were grown by different techniques (ALMBE and MBE), at different growth temperatures and by using growth interruptions. Both AFM and PL show that the ALMBE is particularly suited to grow relatively large dots with sharp size distributions at relatively large InAs coverages without incurring dot coalescence. Moreover, the low temperature ALMBE growth of caps reduces the interaction between dots and caps. The control of dot sizes and of dot/cap interaction results in PL emissions shifted towards the spectral windows of photonic interest. In particular, structures with ALMBE dots and with optimized confining layers show a significantly bright emission at 1.26 mu m at 300 K.