CdTe/Zn 1−x Mg x Te self-assembled quantum dots: Towards room temperature emission

Abstract

We report the dependence of the growth and the optical properties of self-assembled CdTe/Zn1−xMgxTe quantum dots on the barrier Mg content x (0⩽x⩽0.3). Due to the decrease of the lattice mismatch between CdTe and Zn1−xMgxTe with increasing x, we use a technique for inducing dot formation, based on efficient reduction of the surface energy by deposition of amorphous Te, which is then desorbed. Mg incorporation in the barriers leads to a better heavy-hole confinement along the growth axis, which is manifested in photoluminescence (PL) studies by both an extension of the radiative regime temperature range (up to 150 K for 30% Mg) and a strong increase of the activation energy for the nonradiative recombination. However, the in-plane confinement is less enhanced, which allows observation of interdot carrier transfer with increasing temperature, as evidenced directly by the analysis of PL intensities for different single dots. Our temperature-dependent data (time-resolved and microphotoluminescence) suggest that this transfer consists of a thermally activated process via the two-dimensional wetting-layer states rather than a direct tunneling (hopping) process.