Optical characteristics of type-II ZnTe/ZnSe quantum dots for visible wavelength device applications

The optical characteristics of type-II ZnTe/ZnSe pyramidal quantum dots (QDs) were theoretically studied as a function of structural parameters such as the band offset, strain, capping layer thickness, and QD thickness. The band bending effect due to the strain dominantly occurs in the QD and the capping layer regions. As a result, the valence band wave function is shifted to the left side of the barrier and the conduction-band wave function is also dominantly located on the left barrier side. The transition energies are redshifted with increasing pyramid base, which is mainly due to a decrease in the valence subband energy. On the other hand, the subband energy in the conduction-band is shown to be nearly independent of the pyramid base length, showing a characteristic of a type-II band structure. Also, the transition energy is found to be nearly independent of the capping layer thickness.