Thin-film CdSe: Photoluminescence and electronic measurements

Abstract

The electronic properties of thin CdSe films prepared through physical vapor transport were investigated using photoluminescence (PL) and electronic measurements. The films were studied at each of the main preparation steps, i.e., evaporation, annealing, etching, and finally photoetching. At 3 K two distinct donor-acceptor (DA) transitions at 1.75 and 1.70 eV were found in the photoluminescence spectra in addition to deep states at about 1.55 eV at 20 K. These DA transitions which are produced mainly during the evaporation might be associated with group VII and with alkali metal impurities. After each preparation step the DA transitions change their intensities. It is shown that photoetching of the films leads to a removal of the deep centers, while the 1.75 eV transition is blue shifted. In contrast with single-crystal CdSe the intensity of the PL increases after photoetching. The results of the PL are consistent with the electronic measurements. They are explained in terms of a previously published model.

Photoluminescence of CdSe nanowires grown with and without metal catalyst

“…Intra-band-gap states giving optical recombinations in the "shallow states" region are commonly referred to as donor-acceptor pairs (DAP, see Table 1) [53,55,[57][58][59]. However, this is quite a generic definition, as both states involved in the process (donor and acceptor) can have a number of different origins (impurities, structural defects, etc.)…”

“…Before considering PL from CdSe NWs, it is important to analyze the PL features in bulk and thin film CdSe [9,[53][54][55][56][57][58][59][60]. An unambiguous match between emission peaks (or bands) measured by different groups is difficult, and a full understanding of the origin of each band is still missing.…”

“…Table 1 summarizes the main PL features for bulk CdSe, as reported in Refs. [9,[53][54][55][56][57][58][59][60]. We classify the bands in various families, according to peak position, lineshape, or suggested literature assignment.…”

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

“…It should be noted that for optoelectronic applications it is very important to have a transparent substrate to the intrinsic (excitonic) light emitted by the active area of thin films. It was found that CdSe films deposited on silicon [4], titanium [5,6] and GaAs [7] substrates manifest intrinsic luminescence, whereas the films deposited on quartz or glass substrates do not show this luminescence [8]. Therefore, it is very important to obtain CdSe films of high optical quality by their deposition on the quartz or glass substrates which are transparent for CdSe intrinsic emission.…”

Study of the correlation between structural and photoluminescence properties of CdSe thin films deposited by close-spaced vacuum sublimation

“…For optoelectronic applications it is also very important to use cheap substrates. Earlier it was found, that CdSe films deposited on silicon [15], titanium [19,20] and GaAs [21] substrates present intrinsic luminescence, whereas the films deposited on quartz substrates do not show this luminescence [22]. Therefore, it is very important to obtain the CdSe films of high optical quality by their deposition on cheap substrates, such as quartz or glass.…”