PERSISTENT SPECTRAL HOLE-BURNING PHENOMENON OF SEMICONDUCTOR QUANTUM DOTS

The persistent spectral hole-burning (PSHB) phenomenon is observed generally in nanocrystalline semiconductors, CdSe, CuCl, and CuBr, embedded in glass and crystal. In the inhomogeneously broadened exciton absorption spectra of these quantum dots, the spectral hole and its associated structure are produced by the narrow-band laser excitation and are conserved for more than several hours at 2 K. The hole depth grows in proportion to the logarithm of the burning fluence. Thermal-annealing and light-induced hole-filling phenomena are observed. The hole burning takes place by tunneling through potential barriers with broadly distributed barrier heights and thicknesses. Photoionization of dots and carrier tunneling into traps in the host are the most probable origins of the PSHB phenomenon. A possible application of the PSHB phenomenon is discussed.