Abstract: Applied electric field dependence of spatially indirect luminescence spectra of N-doped ZnSe/BeTe/ZnSe type-Ⅱ quantum wells was studied. Experimental results indicate that each of the luminescence spectra exhibits a main luminescence peak with a lower linear polarization degree. This phenomenon can be attributed to the equalizing potential of both wells, which is due to the screening of the built-in electric field caused by the doped electrons in the structure. Meanwhile, each of the luminescence spectra exhibits an asymmetry peak with an inverse-Boltzmann line-shape, and the line-shape and linear polarization degree remain unchanged within the entire voltage range. However, the integrated luminescence intensity depends strikingly on various external voltages: with changing the positive gate voltage (in the range of +7 V to 0 V), the integrated luminescence intensity almost maintains a constant, but with increasing negative gate voltage (-1 V to -7 V), the integrated luminescence intensity reduces significantly. These behaviors indicate that the spatially indirect luminescence spectra show a characteristic feature for a negatively charged exciton transition. The constant integrated luminescence intensity is explained as screening of the applied electric field with the doped layer, while the significantly reduced integrated luminescence intensity is ascribed to excitation of doping electrons by applied electric field (leading to a decrease in the electron concentration in the region excited by laser), thus resulting in a reduction in the number of negatively charged exciton. In addition, the possible particle configuration of the spatially indirect negatively charged exciton was also explored.

Key words: photoluminescence, charged exciton, quantum well, electric field, N-doped ZnSe/BeTe, linear polarization degree