Electrical and optical properties in sputtered GaSe thin films

Polycrystalline β-GaSe thin films were obtained by the thermal evaporation of GaSe crystals onto glass substrates kept at 300 o C under a pressure of 10 -5 Torr. The transmittance and reflectance of these films was measured in the incident photon energy range of 1.1-3.70 eV. The absorption coefficient spectral analysis in the sharp absorption region revealed a direct allowed transitions band gap of 1.83 eV. The data analysis allowed the identification of the dispersive optical parameters by calculating the refractive index in the wavelength region of 620-1100 nm. In addition, the photocurrent of the samples was studied as function of incident illumination-intensity and temperature. The photocurrent is found to exhibit sublinear and supralinear character above and below 270 K, respectively. The temperature dependent photocurrent data analysis allowed the calculation of photocurrent activation energies as 603, 119 and 45 meV being dominant in the temperature regions of 250-300 K, 180-240 K and 80-160 K, respectively.

Section: Room Temperature Optical Parametersmentioning

confidence: 99%

Section: Fig 2 Plot Of (αE)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Optoelectronical properties of polycrystallineβ -GaSe thin films

Qasrawi

Ahmad

2006

“…Namely, most of the works give attention to the structural and electrical properties of which. As for example, GaSe thin films has been grown using different types of substrates at various substrate temperatures using several growing techniques [6][7][8][9]. The published data has driven a good idea about the electrical and structural properties of GaSe thin films.…”

Section: Introductionmentioning

confidence: 99%

Refractive index, band gap and oscillator parameters of amorphous GaSe thin films

Qasrawi

2005

GaSe thin films are obtained by evaporating GaSe crystals onto ultrasonically cleaned glass substrates kept at room temperature under a pressure of ~10 -5 Torr. The X-ray analysis revealed that these films are of amorphous nature. The reflectance and transmittance of the films are measured in the incident photon energy range of 1.1-3.0 eV. The absorption coefficient spectral analysis revealed the existence of long and wide band tails of the localized states in the low absorption region. The band tails width is calculated to be 0.42 eV. The analysis of the absorption coefficient in the high absorption region revealed an indirect forbidden band gap of 1.93 eV. The transmittance analysis in the incidence photon wavelength range of 500-1100 nm allowed the determination of refractive index as function of wave length. The refractive index-wavelength variation leads to the determination of dispersion and oscillator energies as 31.23 and 3.90 eV, respectively. The static refractive index and static dielectric constant were also calculated as a result of the later data and found to be 9.0 and 3.0, respectively.

Influence of density of states on optical properties of GaSe thin film

Thamilselvan

Premnazeer

Mangalaraj

et al. 2004

A systematic investigation on the effect of substrate temperature on the structure, optical absorption and density of states of vacuum evaporated gallium monoselenide (GaSe) thin films is reported. The X-ray diffraction analysis shows an occurrence of amorphous to polycrystalline transformation in the films deposited at higher-temperature substrates (573K). The compositional analysis is made with Auger Electron Spectroscopy (AES). The thickness of the film (175nm) is measured by a multiple beam interferometery. Optical characteristics of the GaSe sample have been analyzed using spectrophotometer in the photon energy range of 1.0 -4 eV. The absorption mechanism has been recognized and the allowed indirect as well as forbidden direct transitions have been found. As-deposited films show two indirect and allowed transitions due to spin-orbit splitting of the valence band, as reported here for the first time. Low field conduction have enabled us to determine the density of states in amorphous and poly-GaSe films. The amorphous and polycrystalline GaSe thin films have localized states density values of N (E F ) = 1.686 × 10 17 cm -3 eV -1 and 1.257 × 10 15 cm -3 eV -1 respectively. The experimental results are interpreted in terms of variations in the density of localized states due to progressive decrease of the unsaturated bonds during deposition.