Optical and photovoltaic properties of indium selenide thin films prepared by van der Waals epitaxy

Abstract

Indium selenide thin films have been grown on p-type gallium selenide single crystal substrates by van der Waals epitaxy. The use of two crucibles in the growth process has resulted in indium selenide films with physical properties closer to these of bulk indium selenide than those prepared by other techniques. The optical properties of the films have been studied by electroabsorption measurements. The band gap and its temperature dependence are very close to those of indium selenide single crystals. The width of the fundamental transition, even if larger than that of the pure single crystal material, decreases monotonously with temperature. Exciton peaks are not observed even at low temperature, which reveals that these layers still contain a large defect concentration. The current-voltage characteristic of indium selenide thin film devices was measured under simulated AM2 conditions. The solar conversion efficiency of these devices is lower than 0.6%. The high concentration of defects reduces the diffusion length of minority carriers down to values round to 0.2 m.

Above-bandgap ordinary optical properties of GaSe single crystal

“…1 With such a unique structural anisotropy, GaSe has long been an interesting material for both experimental [1][2][3][4][5][6][7][8][9][10][11][12] and theoretical 1, [13][14][15] physics studies, and GaSe and related III-VI compounds have received considerable attention for their potential applications in various device structures. [16][17][18][19][20] Furthermore, advances in van der Waals epitaxy 21 have made it possible to grow single-phase high-quality III-VI compound thin films that renewed interests in GaSe.…”

Angle-resolved photoemission study and first-principles calculation of the electronic structure of GaTe

“…[3][4][5][6] Among these compounds, GaTe is one of the less studied because it presents a higher anisotropic and more complex crystal structure than the rest of the III-VI materials. GaTe belongs to the B2/m space group and has a base centered monoclinic unit cell.…”

Ellipsometric study of single-crystal γ-InSe from 1.5 to 9.2 eV

“…1,2 With the bulk of the solar spectrum occurring at photon energies greater than 1.2 eV, a knowledge of its above-band gap optical properties is obviously important not only to design solar cells but also to verify theoretical calculations of the electronic energy band structure. While a limited number of optical studies have been done on InSe, mainly by reflectance techniques, [3][4][5] no systematic investigation of the dielectric response of this material has yet been reported.…”

“…It was prepared by cutting the ingot into a rectilinear 8 ϫ 8 ϫ 0.2 mm 3 block with the large faces normal to the ͓001͔ direction. The VUV-SE is a rotating-analyzer type equipped with a computer-controlled MgF 2 Berek compensator to improve accuracy, particularly below the band gap. The angle of incidence was 67°.…”