Three-dimensional assemblies of semiconductor quantum dots in a wide-gap matrix providing an intermediate band for absorption

摘要

We consider a self-assembled quantum dot (QD) system consisting of the QD itself, the wetting layer and the matrix on a substrate. The electronic structure for various Ⅲ-Ⅴ material combinations was determined by atomistic empirical pseudopotential calculations. Taking the widely investigated InAs/GaAs/GaAs(001) system as benchmark, we analyze the changes induced in the energy levels and offsets relevant for a QD-based intermediate band solar cell (IBSC). We explore the effects of (ⅰ) the dot material, (ⅱ) the matrix material, and (ⅲ) dot-matrix-substrate combinations that may enable strain balanced structures. Using as unique reference criterion the relative position of the intermediate band inside the band gap of the matrix, we suggest the dot/ matrix/substrate combinations InAs/(In,Ga)P/GaAs(001), In(As,Sb)/GaAs/InP(001), and InAs/ Ga(As, Sb)/InP(001) as promising candidates for QD-IBSCs.