Investigation of Localized Levels in GaS0.5Se0.5 Layered Crystals by Means of Electrical, Space-Charge Limited Current and Photoconductivity Measurements

Abstract

To identify the localized levels in GaS0.5Se0.5 single crystals, the dark electrical conductivity, current–voltage characteristics and photoconductivity measurements were carried out in the temperature range of 250–400 K. Temperature dependence of dark electrical conductivity and the space‐charge limited current studies indicate the presence of a single discrete trapping level located at 0.31 eV below the conduction band with a density of about 1.3 × 1015 cm—3. The conductivity data above 320 K reveal an additional donor level with activation energy of 0.40 eV indicating the extrinsic nature of conduction. The spectral distribution of photocurrent in the photon energy range of 0.65—5.9 eV reveals an indirect band gap of 2.26 eV. The photocurrent–illumination intensity dependence follows the law Iph ∝ Fγ, with γ being 1.0, 0.65, and 0.5 at low, moderate and high illumination intensities, respectively. The corresponding behavior indicates the domination of monomolecular recombination, near equal densities of trapped and recombination centers and bimolecular recombination. It is observed that the photocurrent increases in the temperature range from 250 K up to Tm = 360 K and decreases for T > Tm. The temperature dependence of the photocurrent reveals two additional impurity levels with activation energies of 0.14 and 0.10 eV below and above Tm, respectively.

Photophysics, photoelectrical properties and photoconductivity relaxation dynamics of quantum-sized bismuth(III) sulfide thin films

“…The study of the phenomenon of photoconductivity is an effective method for understanding band structures of investigated semiconducting materials [6,28,37,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. Using the photoconductivity measurements, information about kinetics of generation, transport and recombination of charge carriers, as well as the density and nature of states in the energy gap due to the presence of impurities and defects can be obtained [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57].…”

“…Using the photoconductivity measurements, information about kinetics of generation, transport and recombination of charge carriers, as well as the density and nature of states in the energy gap due to the presence of impurities and defects can be obtained [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. The phenomenon of photoconductivity of semiconductors is due to the intrinsic photoeffect i.e.…”

“…In a general case, it can be shown that photoconductivity ðDsÞ can be expressed as a power function of the light intensity (I) or the flux of the incident light ðFÞ [36,41,42,58]:…”

“…The case of 0.5oko1 is often referred to as a sublinear behavior. According to the several models proposed in the literature for such a regime [41,42,58], a value of the exponent k between 0.5 and 1 strongly indicates an exponential distribution of impurity levels in the forbidden band (the so-called exponential trap distribution). In other words, the trap states density exhibits an exponential dependence on energy [41,42,58].…”

Eco-friendly visible-wavelength photodetectors based on bandgap engineerable nanomaterials

“…According to the models proposed in the previous literature, n with a value between 0.5 and 1 indicates that the trap state density exhibits an exponential dependence on energy. 25,26 In the present InSe photodetector, a power dependence of $0.67 implies the existence of an exponential trap distribution.…”