Hopping conduction in polycrystalline semiconductors

Sharma, Raman; Shukla, Abhay; Kapoor, A. K.; Srivastava, R. S.; Mathur, P. C.

doi:10.1063/1.334390

Cited by 27 publications

(10 citation statements)

References 19 publications

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“…In other polycrystalline semiconductors also, such as in InSb and CdTe, the density of grain boundary states have been found to be appreciable. 28 With the above values of the density of states, reported for different polycrystalline materials and a common experience of interface state density encountered in layered structures such as Schottky contacts, 29,30 this parameter cannot be ignored for the interpretation of physical properties of the material. In the present case of polycrystalline CdS, the density of grain boundary states has been reported to be quite large.…”

Section: Resultsmentioning

confidence: 92%

On the sub-band gap optical absorption in heat treated cadmium sulphide thin film deposited on glass by chemical bath deposition technique

Chattopadhyay

Karim

Roy

2013

Journal of Applied Physics

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The sub-band gap optical absorption in chemical bath deposited cadmium sulphide thin films annealed at different temperatures has been critically analyzed with special reference to Urbach relation. It has been found that the absorption co-efficient of the material in the sub-band gap region is nearly constant up to a certain critical value of the photon energy. However, as the photon energy exceeds the critical value, the absorption coefficient increases exponentially indicating the dominance of Urbach rule. The absorption coefficients in the constant absorption region and the Urbach region have been found to be sensitive to annealing temperature. A critical examination of the temperature dependence of the absorption coefficient indicates two different kinds of optical transitions to be operative in the sub-band gap region. After a careful analyses of SEM images, energy dispersive x-ray spectra, and the dc current-voltage characteristics, we conclude that the absorption spectra in the sub-band gap domain is possibly associated with optical transition processes involving deep levels and the grain boundary states of the material.

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Section: Resultsmentioning

confidence: 92%

On the sub-band gap optical absorption in heat treated cadmium sulphide thin film deposited on glass by chemical bath deposition technique

Chattopadhyay

Karim

Roy

2013

Journal of Applied Physics

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“…Carrier transport through these states therefore necessarily requires that they form percolated networks that support hopping conduction. Evidence of variable range hopping in both poly-CdTe and Cu(In,Ga)Se 2 materials has been detected via electrical measurements, which reveals a large drop in the conductivity and mobility at lower temperatures and a transition to a regime that follows a exp( T −1/4 ) behaviour 24 25 26 27 28 . Hall measurements are often difficult to perform on p -type poly-CdTe films because of their low free-carrier concentrations and mobility.…”

Section: Resultsmentioning

confidence: 99%

Measuring long-range carrier diffusion across multiple grains in polycrystalline semiconductors by photoluminescence imaging

et al. 2013

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Thin-film polycrystalline semiconductors are currently at the forefront of inexpensive large-area solar cell and integrated circuit technologies because of their reduced processing and substrate selection constraints. Understanding the extent to which structural and electronic defects influence carrier transport in these materials is critical to controlling the optoelectronic properties, yet many measurement techniques are only capable of indirectly probing their effects. Here we apply a novel photoluminescence imaging technique to directly observe the low temperature diffusion of photocarriers through and across defect states in polycrystalline CdTe thin films. Our measurements show that an inhomogeneous distribution of localized defect states mediates long-range hole transport across multiple grain boundaries to locations exceeding 10 μm from the point of photogeneration. These results provide new insight into the key role deep trap states have in low temperature carrier transport in polycrystalline CdTe by revealing their propensity to act as networks for hopping conduction.

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“…Then a possibility for conduction is by the hopping of charge carriers from filled trap states to the empty trap states. The filled states may subsequently release the electrons and thus hop in conduction [21].…”

Section: Low Field Conductionmentioning

confidence: 99%

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

Thamilselvan

Premnazeer

Mangalaraj

et al. 2004

Cryst. Res. Technol.

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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.

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Hopping conduction in polycrystalline semiconductors

Cited by 27 publications

References 19 publications

On the sub-band gap optical absorption in heat treated cadmium sulphide thin film deposited on glass by chemical bath deposition technique

On the sub-band gap optical absorption in heat treated cadmium sulphide thin film deposited on glass by chemical bath deposition technique

Measuring long-range carrier diffusion across multiple grains in polycrystalline semiconductors by photoluminescence imaging

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

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