Photoluminescence studies in epitaxial CZTSe thin films

Abstract

Epitaxial Cu 2 ZnSnSe 4 (CZTSe) thin films were grown by molecular beam epitaxy on GaAs(001) using two different growth processes, one containing an in-situ annealing stage as used for solar cell absorbers and one for which this step was omitted. Photoluminescences (PL) measurements carried out on these samples show no dependence of the emission shape on the excitation intensity at different temperatures ranging from 4 K to 300 K. To describe the PL measurements, we employ a model with fluctuating band edges in which the density of states of the resulting tail states does not seem to depend on the excited charge carrier density. In this interpretation, the PL measurements show that the annealing stage removes a defect level, which is present in the samples without this annealing. Published by AIP Publishing. [http://dx

Optical Signatures of Impurity–Impurity Interactions in Copper Containing II–VI Alloy Semiconductors

“…Such band tails have been studied qualitatively by optical spectroscopy: mainly photoluminescence (PL) as a function of temperature and excitation power [11][12][13][14][15][16][17] , but also by PL excitation spectroscopy (PLE), which reveals the density of states in the presence of potential fluctuations 18,19 , and by time-resolved photoluminescence spectroscopy (TR-PL), which gives information about the localization and transfer of carriers between the band tail states, as was done on CZTS single crystals 16,19 : all these data have been analyzed as a function of the order/disorder degree in the quaternary structure 19,20 .…”

Investigation on the properties of Cu 2 ZnSnSe 4 and Cu 2 ZnSn(S,Se) 4 absorber films prepared by magnetron sputtering technique using Zn and ZnS targets in precursor stacks

“…The peaks were centered at 1.28 and 1.31 eV for the samples A1 and A2, respectively, and the slopes of the peaks were greater on the low energy side than the high energy side for both samples. According to the theory of heavily doped semiconductor materials, such asymmetrical shape of PL bands is an indication of the presence of spatial electrostatic potential fluctuations which originate from the high concentration of randomly distributed charged defects in the material and these electrostatic potential fluctuations lead to the formation of band tails in the electronic band structure 80,81 . PL bands give information about the types of radiative recombination occurring through different channels such as band‐to‐tail (BT), band‐to‐band (BB), band‐to‐impurity (BI), and donor‐acceptor pair in the material 80,82 .…”

“…According to the theory of heavily doped semiconductor materials, such asymmetrical shape of PL bands is an indication of the presence of spatial electrostatic potential fluctuations which originate from the high concentration of randomly distributed charged defects in the material and these electrostatic potential fluctuations lead to the formation of band tails in the electronic band structure. 80,81 PL bands give information about the types of radiative recombination occurring through different channels such as band-to-tail (BT), band-to-band (BB), band-to-impurity (BI), and donoracceptor pair in the material. 80,82 The observed PL emission bands in our study were attributed to BB transition which arises from the recombination of free electrons with free holes and corresponds to the band gap energy (E g ).…”

Optical determination of the band gap and band tail of epitaxial Ag2ZnSnSe4 at low temperature

“…Such band tails have been studied qualitatively by optical spectroscopy: mainly photoluminescence (PL) as a function of temperature and excitation power [11][12][13][14][15][16][17] , but also by PL excitation spectroscopy (PLE), which reveals the density of states in the presence of potential fluctuations 18,19 , and by time-resolved photoluminescence spectroscopy (TR-PL), which gives information about the localization and transfer of carriers between the band tail states, as was done on CZTS single crystals 16,19 : all these data have been analyzed as a function of the order/disorder degree in the quaternary structure 19,20 .…”