Investigation of type-II Ga(As)Sb/GaAs quantum dots embedded in an InGaAs quantum well for solar cell applications

We theoretically investigate the electronic and optical properties of charge carriers in type-II Ga(As)Sb/GaAs quantum dots (QDs) embedded in an InGaAs quantum well (QW), to determine their viability for use in intermediate band solar cell (IBSC) devices. This hybrid structure has the advantage of allowing a large flexibility to alter wave function distribution of the electron ground state, which is often considered as an intermediate band (IB) in QD-IBSC. The polarized transitions dipole moment (TDM), the polarized absorption coefficients and the radiative lifetime were studied as a function of QD height. Our theoretical results show an enhancement of inter-band absorption spectrum with a redshift of the peak corresponding to
transition and a blueshift of the peak, as the height of QD increases. The intra-band light absorption spectrum exhibits a redshift and its magnitude remains almost unchanged, as the height of QD increases. Furthermore this structure provides strong intra-band light absorption comparable to that of type-I QDs and equivalent to transition strength. A long carrier lifetime in IB of about was found, but remains more than an order of magnitude less than the inter-band radiative time due to the low confinement potentials of the electron along the -axis in this type-II dot-in-well (DWELL) structure.