Wetting Layer Effect on Optical Gain of Strained CdTe/ZnTe Pyramidal Quantum Dots

The optical properties of strained CdTe/ZnTe pyramidal quantum dots (QDs) are investigated as a function of the wetting layer thickness using an eight-band strain-dependent k^.p Hamiltonian. The ground-state subband energies in the conduction and valence bands rapidly decreases with the increasing wetting layer thickness. This is attributed to the reduction of subband energies in both the conduction and the valence bands due to the strain effect. The optical gain peak on the shorter wavelength side decreases with the increasing wetting layer thickness. On the other hand, the gain peak on the longer wavelength side is nearly independent of the wetting layer thickness. The decrease in the gain peak on the shorter wavelength side is related to the decrease in matrix elements corresponding to transitions between higher subbands such as (3,4) and (4,3).