Effect of Bi addition on the electrical properties ofa-Ge–Se–In thin films

Abstract

This paper reports on the steady state and transient photoconductivity of Ge20Se70−xIn10Bix (x = 2, 4, 6, 8, 10) thermally evaporated thin films. The dark conductivity (σd) increases with the increase in the Bi content. The value of σd increases slowly from x = 2 to x = 6, but for x ⩾ 8 the increase is quite abrupt. Photoconductivity (σph) also increases with the increase in the Bi content. The dark activation energy (ΔEd) decreases with the increase in the Bi content. There is a drop in the photosensitivity (σph/σd) of films with the increase in Bi addition. The result of the intensity dependent steady state photoconductivity (σph) follows the power law with intensity (F), i.e. σph α Fγ where the value of γ is close to 0.5, suggesting the predominance of bimolecular recombination in these materials. The rise and decay of photocurrent show the increase in the differential lifetime (τd), with the increase in the Bi content, indicating a delay in the recombination rate of photo-generated charge carriers. This change is governed by the photo-generated carriers trapped in the intrinsic defects or light induced defect creation through structural changes. One can therefore also expect that the density of states increases with the increase in the Bi content in amorphous thin films. The dispersion parameter (α) of the localized state energy distribution, determined from the decay curves, is also reported.

Facile Synthesis of Mesoporous TiO2Spheres with Hollow Interiors

“…It can be seen that the absorption edge of the TiO 2 hollow spheres annealed at 500 • C and 900 • C showed a red shift in comparison with that of the commercial anatase and rutile TiO 2 powders, which may be due to the increased refractive index. 37,38 Also, the reflectivity of our synthesized TiO 2 spheres is higher than that of commercial one, which can be thought as a spherical morphology effect on reflection.…”

ELECTRICAL AND PHOTOELECTRICAL PROPERTIES OF A-Ge20Te80-xBix (x = 0, 1.5, 2.5, 5.0) THIN FILMS

“…The localized states induced by these defect states acts as trapping centers. These traps 'store' the charge carrier and hence delay the recombination rate corresponding to the increase in the differential lifetime with the increase in the Bi content [25]. According to the trap controlled recombination model [26], the photocurrent decay depends on the initial density of photogeneration pulse when the total filling of gap states is not achieved.…”

Analysis of glass forming ability using percolation concept and tunability of physical parameters of a-Ge12Se76-xAs12Bixglassy semiconductors

“…It has been reported that when the Ge content is 20 at.%, the maximum of Bi content which can be incorporated into the Ge-Se matrix, is only 13 at.% [18]. Moreover, with the increase in Bi content from 0 to 10 at.%, a sharp change is observed in optical band gap and electrical activation energy, approximately around 8 at.% to 9 at.% of Bi [19,20]. The composition at lower Bi content exhibits luminescence, while the composition showing n-type conduction fails to exhibit it [21].…”