Temperature dependence of the energy gap, refractive index and optical‐oscillator parameters of amorphous Ga_xSe_1–x (x = 0.4, 0.5, 0.6) thin films

Abstract

Thin films of a‐GaxSe1–x (x = 0.4, 0.5, 0.6) are prepared by vacuum evaporation technique onto well‐cleaned glass substrates. The transmittances of the films are measured at various temperature ranges (100 K‐400 K) in the wavelength range of 400‐1100 nm. Optical absorption obeyed the non‐direct transition process. The temperature dependence of the optical energy gaps in that range are fitted with four equations beginning with linear, non linear, Varshni and Bose Einstein equations. The results have got appeared the best fitting is with the Varshni equation. We have found that the energy gap decreases with the increase in Ga percentage in these thin films and increase in energy gap with the decrease of temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electronic and optical properties of amorphous GaSe thin films

“…The values found for the dispersive and oscillator energies were E d ¼ 18:6 AE 0:4 eV and E 0 ¼ 4:00 AE 0:09 eV, respectively. Mustafa et al [8] It is interesting to note that the relation E 0 % 2:0E g [26] is verified in our case.…”

“…The substitution of P still preserving the low vapor pressure of the alloy, but increasing the chemical stability of the material would be highly desirable when aiming at device applications. A possible candidate is Ga, since Ga-Se alloys have very interesting properties, such as wide spectral transparency, ranging from 0.65 to 18 lm [3], high nonlinear coefficients [4,5] and large optical gaps [6][7][8][9][10][11][12][13].…”

“…These values can be compared with other results found in the literature. Considering only amorphous films, Mustafa et al[8] found indirect allowed…”

Structural and thermal investigations of an amorphous GaSe9 alloy using EXAFS, cumulant expansion, and reverse Monte Carlo simulations

“…8 Alloys of this system have very interesting properties, such as wide spectral transparency, ranging from 0.65 to 18 µm, 9 high nonlinear coefficients, 10,11 and large optical gaps. [12][13][14][15] Such properties are associated with their atomic structures. In GaSe, the structure is formed by bidimensional layers of hexagons in which Se and Ga atoms occupy alternate corners.…”

“…Different methods can be used to produce Ga-Se alloys in bulk, powder or thin films forms, such as chemical vapour deposition, 6 molecular beam epitaxy, 17 melt-quenching (MQ), 13,14,[18][19][20][21] Bridgman method, [22][23][24][25] vacuum evaporation, 13,14,26 and mechanical alloying (MA). 15,27,28 Many experimental techniques were used to investigate optical (transmittance, reflectance and absorption spectroscopies, [13][14][15]23,26 ellipsometry 25 ), vibrational (Raman spectroscopy 15,27,29 ), electrical (conductivity 26 ), thermal, 15,[18][19][20][21]27,28 and photothermal 28 properties of Ga-Se alloys. Since many of these properties are related to their atomic structures, investigation of structural properties in order to detera) kleber@fisica.ufpr.br mine average interatomic distances, coordination numbers, disorder, and asymmetry of the partial pair distribution functions g i j (r) becomes an important task, and experimental techniques such as x-ray diffraction (XRD) [30][31][32] and EXAFS 33,34 can be used to extract such information.…”