Defect-induced enhancement of absorption coefficient and electroabsorption properties in GaN/AlGaN centered defect quantum box (CDQB) nanocrystal

In this paper, effect of an introduced cubic defect on electrical and optical properties of cubic quantum dot is studied. Self-consistent solution of the Schrödinger-Poisson equations for evaluation of the proposed complex quantum dot is used. Optical properties (absorption and electroabsorption properties associated with intersublevel transition) of the proposed structure are also investigated using density matrix method. Effects of defect size on energy levels, carrier density, matrix element and optical linear absorption coefficient of centered defect quantum box (CDQB) are examined. It is shown that with increasing the defect size a considerable enhancement in magnitude of the absorption coefficient and also red-shift in resonance frequency are achievable. We show that the CDQB has higher absorption peak (at least 80 times) and tunable absorption spectra, due to increase of the matrix element and modified energy sublevels, compared quantum box structure without defect. Also, it is shown that the defect enhances electroabsorption properties (modulation bandwidth and the maximum variation of absorption peak with external field) of the quantum box structure.