Photoluminescence of high optical quality CdSe thin films deposited by close-spaced vacuum sublimation

Polycrystalline CdSe thin films (d=0.1―3.0 μm) have been deposited on a glass substrate by means of the close-spaced vacuum sublimation technique. X-ray diffraction measurements have shown that the films obtained at Ts > 473 K have only wurtzite phase. The influence of deposition conditions, in particular, the substrate temperature on the photoluminescence (PL) of CdSe films spectra was investigated. This let us study the effect of glass substrate on their optical quality as well as determine the nature and energy structure of the intrinsic defects and residual impurities in the films. The presence in PL spectrum of the most intense sharp donor bound exciton D0X-line for CdSe films obtained at Ts=873 K indicates the n-type conductivity and their high optical quality. Intensive PL bands in the spectral range 1.65―1.74 eV were also observed, which are associated with the recombination of donor―acceptor pairs with the participation of the shallow donor and acceptor centers caused by Na(Li) residual impurities. As a result of the study of the PL spectra of CdSe films the optimal temperature conditions of their growth were determined, namely, the substrate temperature Ts= 873 K and the evaporator temperature Te=973 K.