Composition Dependence of the Band Gap of CuInS_2xSe_2(1−x)

Abstract

The A' B' I' C;' semiconducting compounds attract great attention due to their potential application in photovoltaic /1/ and infrared non-linear optical devices /2/. In this connection it is interesting to study the properties of their solid solutions. The purpose of this note is to study the composition dependence of the band gap of CuInS2xSe2(1 been reported in /3 to 6/. solid solutions, some properties of which haveThe transmission spectra in the range from 6000 to 14000 cm-' were taken using a SP-700 C spectrophotometer as well as a special apparatus for spectra recording with wavelength modulation. All investigations were carried out on single crystal samples obtained by the chemical transport /6/ and two-temperature synthesis /7/. For measurements the specimens were polished and lapped from one side to a thickness of about 100 pm. The absorption coefficient a was calculated using the estimated transmission T and the reflectivity R given in /8/ by the well-known expression a = - R2]1'2]) where d is the sample thickness. The ternary chalcopyrite compounds Abrn%" being direct-gap semiconductors, the band gap E was determined by extrapolation of the linear part of (a -. ad) versus photon energy to the intersection with the photon energy axis. In wavelength-modulated experiments the band gap was determined by the position of the maximum in the dI/dh. spectrum. The measurements made with polarized light showed E to be independent of polarization or, in other words, the absorption processes near the absorption edge are independent of the polarization of irradiation, what is related by us to the absence of tetragonal distortion of the unit cell in the investigated system (for CuInS2 c/a = 2.015 and for CuInSe2 c/a * 2.003). 2 g g 1) Podlesnaya 1.7, 220726 Minsk, USSR.

Compound semiconductor alloys: From atomic-scale structure to bandgap bowing

“…For each of the two Ga compounds, the Cu-VI and Ga-VI bond lengths are very similar as can be seen from 37,38,44,[251][252][253][254][255][256][257] The variation of the values is typically less than 10%.…”

Copper Indium Selenides and Related Materials for Photovoltaic Devices

“…The bandgap dependence on composition has been reported by several researchers, with the reported optical bowing parameters varying from 0 to 0.88. [145][146][147] There is substantially better agreement between a larger number of studies of the mixed-anion alloy CuGa(Se X S 1-X ) 2 that the optical bowing parameter in that system is zero. 148, and references therein It has been argued that the bond-alternation, which leads to optical bowing in mixed-cation ternary chalcopyrite alloys, does not occur in the mixedanion alloys, 149 and that the bowing parameter therefore should vanish in CuIn(Se X S 1-X ) 2 , as reported by Bodnar and co-workers.…”

“…148, and references therein It has been argued that the bond-alternation, which leads to optical bowing in mixed-cation ternary chalcopyrite alloys, does not occur in the mixedanion alloys, 149 and that the bowing parameter therefore should vanish in CuIn(Se X S 1-X ) 2 , as reported by Bodnar and co-workers. 145 The substantial uncertainty and disagreement among the published experimental results suggests that resolution of this question will require further investigation.…”

Processing of CuInSe2-Based Solar Cells: Characterization of Deposition Processes in Terms of Chemical Reaction Analyses. Final Report, 6 May 1995 - 31 December 1998

“…The bandgap dependence on composition has been reported by several researchers, with the reported optical bowing parameters varying from 0 to 0.88 [123][124][125]. There is substantially better agreement between a larger number of studies of the mixed-anion alloy CuGa(SeXS1-X)2 that the optical bowing parameter in that system is zero [126, and references therein].…”

“…There is substantially better agreement between a larger number of studies of the mixed-anion alloy CuGa(SeXS1-X)2 that the optical bowing parameter in that system is zero [126, and references therein]. It has been argued that the bond-alternation which leads to optical bowing in mixed-cation ternary chalcopyrite alloys does not occur in the mixed-anion alloys [127], and that the bowing parameter should therefore vanish in CuIn(SeXS1-X)2 as reported by Bodnar and coworkers [123]. The substantial uncertainty and disagreement amongst the published experimental results suggests that resolution of this question requires further investigation.…”