Photoluminescence Properties of CuGaSe₂Grown by Iodine Vapour Transport

Abstract

The photoluminescence spectra of CuGaSe2 are measured on melt-solidified crystals, iodine vapour transported as-grown crystals and annealed crystals in various conditions. From the change in the spectra among them and the influence of annealing on luminescence, it is concluded that the iodine impurity acts as a deep donor which has been unintentionally incorporated into crystals during growth, and that the selenium vacancy acts as a shallow donor. The latter defect can be filled back by annealing in selenium vapour at 600°C. All photoluminescence bands observed in the iodine vapour transported crystals are explained in trems of these two donors (0.38 eV and 80 meV) and one acceptor (40 meV), which is probably due to the copper vacancy.

Optical properties of CuGaSe2 and CuAlSe2 layers epitaxially grown on Cu(In0.04Ga0.96)Se2 substrates

“…PL peaks due to transitions from the conduction band to acceptor ͑interstitial Se atom: E A ϭ40 meV) at 1.68 eV 31,32 and donor ͑Se vacancy: E D ϭ80 meV) to valence band at 1.63 eV 33,34 have been reported. The peak at 1.62 eV ͑corresponding to the peak at 1.63 eV͒ found in Cu-rich CuGaSe 2 /GaAs prepared by MBE 29,35 has been assigned to both the D -A pair transition and the donor to valence band transition associated with the selenium vacancy (E D ϭ108 meV).…”

Deep level emission in polycrystalline CuGaSe2 thin-films observed by micro-photoluminescence

“…Appearance of the dominant peak around 1.60 eV is in consistent with findings of various research groups, and named as DAP1 in this study. [13][14][15][16] An emission, DAP2 at lower-energy side with asymmetric and broadened peak around 1.35 eV was observed as shown in the figure. In addition, a deep-level emission apparent around a broad range of 0.9-1.1 eV has been observed, and has been named as DL.…”

“…Among those PL studies, two intrinsic point defects were mainly reported previously: a 50 meV acceptor level and an 80-100 meV donor level, which were attributed to Cu vacancies (V Cu ) and Se vacancies (V Se ), respectively. 13,14) Later, the model of three shallow acceptors (60 ± 10, 100 ± 10, 150 ± 10 meV) and one shallow donor (12 ± 5 meV) were reported to describe the recombination paths in slightly Cu-rich and nearly stoichiometric CuGaSe 2 films epitaxially grown on GaAs. 15,16) Only few studies reported on more deeper emission, originated from donor-acceptor-pair (DAP) recombination, observed between 1.0 and 1.3 eV in PL spectra of single crystal and poly-CuGaSe 2 , [17][18][19] and recently in epitaxially grown CuGaSe 2 .…”

Wide-Gap Chalcopyrites

“…This is followed by either of two or both transitions around 1.66-1.69 and 1.62-1.63 ev, which are interpreted as FB or DA transitions (see e.g., [80, 82-87, 90, 91, 97, 99-105]), although some authors report more individual transitions in this energy region. A deeper defect-related transition around 1.56-1.60 ev has been reported as well (see e.g., [81,[83][84][85]91,100,101,[103][104][105]), together with a number of deeper transitions, which have been attributed to deeper defects [100,106] or to potential fluctuations [103]. These general patterns are similar to those obtained in CuInSe 2 -a fact that has been ignored in the literature until recently [77,107].…”