Deep defect related photoluminescence in heavily doped CuGaTe₂ crystals

Abstract

CuGaTe 2 samples very often exhibit optical and electrical properties of heavily doped semiconductors. This paper investigates the low temperature photoluminescence properties of polycrystalline CuGaTe 2 samples. The photoluminescence spectra of "heavily doped" semiconductors are usually characterized by the broadening of the photoluminescence bands that is caused by the fluctuations of the forbidden band edges. The deep photoluminescence region observed (0.8 -1.3 eV) consists of two peaks. One of them is located at 0.955 eV and has been reported before. Another, totally new band was discovered at 1.14 eV. The low-temperature j-shift of both bands was detected. Also, rather significant blue shift with the increasing temperature was noticed. It is proposed that both bands consist of two recombination channels. At low temperatures tail-to-impurity recombination dominates. As the temperature increases, the tail-toimpurity recombination transforms into band-to-impurity recombination.

Tailoring of Bound Exciton Photoluminescence Emission in WS2 Monolayers

“…It is also observed that the band blueshifts as the excitation intensity increases and the rate of this shift is about 15 meV per decade of laser power (Figure b). This kind of blueshift is usually considered as the evidence of disorder‐related effects in semiconductors . We showed before that the random fluctuations of defect concentration or strain can cause band gap and potential fluctuations and form exponential tails in the density of localized states extending into the band gap.…”

Research in solar cell technologies at Tallinn University of Technology

“…In recent years we have studied excitonic emission in CuInS 2 , including also a very deep emission related to the isoelectronic defects [3,4]. The edge emission resulting from highly doped ternaries has been studied experimentally and theoretically in AgGaTe 2 [5], CuGaTe 2 [6], AgInTe 2 [7], CuInTe 2 [8], and in other ternaries. The ordered defect compounds (ODC) have also attracted considerable interest not only because of their potential role in high-efficiency photovoltaic devices, but also as regards the understanding of structural properties of chalcopyrite ternary compounds.…”