Steady-state photoconductivity in amorphous selenium glasses

Qamhieh, Naser; Benkhedir, M. L.; Brinza, Monica; Willekens, J; Adriaenssens, Guy

doi:10.1088/0953-8984/16/23/003

Cited by 15 publications

(18 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The two recombination regimes discussed in Section 3.2 are effectively observed in the data, with activation energies of DE m = (0.35 ± 0.06) eV and DE b = (0.19 ± 0.03) eV. These energy values agree with the ones extracted earlier from a similar a-Se sandwich cell that was illuminated with a near-infrared lightemitting diode at 890 nm [14]. Error estimates are based on the combined results of three different samples, and not just the data of Fig.…”

Section: Steady-state Photocurrentssupporting

confidence: 87%

“…The thermally accessible levels of the negative-U defects are also instrumental in carrier recombination in chalcogenide semiconductors [10], such that their energy positions in the gap can be derived from the temperature dependence of steady-state photocurrent measurements [11,12]. Following the successful use of this method for several arsenic chalcogenides [13], Qamhieh et al [14] made use of it to pin down the corresponding energy levels in a-Se. An expected change-over from bimolecular to monomolecular recombination was seen with rising temperatures, and acceptable values for the energy levels were obtained, but large uncertainties persist on the values of deduced current activation energies and, hence, on the positions of localized states.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Defect levels in the band gap of amorphous selenium

Benkhedir

Aida

Adriaenssens

2004

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

Section: Steady-state Photocurrentssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Defect levels in the band gap of amorphous selenium

Benkhedir

Aida

Adriaenssens

2004

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

“…The break in the 67 ppm TPC traces to a steeper decay around t ≈ 10 −5 s signals carrier trapping into a further set of defects states. In fact, the presence of an important set of deep traps in a-Se has been demonstrated by early xerographic residual potential measurements [21], as well as more recent photocurrent simulations [20] and measurements [8].…”

Section: Ppm-doped Samplesmentioning

confidence: 94%

“…Given that measurements of a-Se photoconductivity in both steadystate and transient modes have been able to clarify the DOS structure of the undoped compound [7][8][9][10] Fig. 1.…”

mentioning

confidence: 99%

Photocurrent measurements in chlorine‐doped amorphous selenium

Benkhedir

Mansour

Djefaflia

et al. 2009

Physica Status Solidi (b)

View full text Add to dashboard Cite

Transient photocurrent (TPC) measurements have been carried out on evaporated a‐Se films doped with either 12.5 or 67 ppm of Cl and compared with analogous measurements on undoped a‐Se samples. The two doping levels lead to strikingly different resulting current traces. While the 12.5 ppm doping level weakens, but does not eliminate the signature of the two hole traps that are observed in the TPC signals of undoped a‐Se, no indication for those levels remains in the 67 ppm Cl‐doped samples. It is argued that suppression of the trap generated by the negative‐U D− centre agrees with the notion that they are being supplanted by doping‐induced Cl− centres. The enhanced density of D+ centres and accompanying cross‐linking of Se chains by those three‐fold coordinated sites leads in turn to the weakening and disappearance of the shallower hole trap ascribed to dihydral angle variations. Results from constant‐photocurrent and time‐of‐flight (TOF) experiments support this interpretation of the TPC observations.

show abstract

“…8b. There have also been steady state photoconductivity measurements on a-Se in the coplanar electroded structure [79], which have been interpreted in terms of recombination centers arising from defects placed at 0.36 eV above E v . In our view, both coplanar steady state and transient photoconductivity measurements on a-Se can easily be dominated by holes diffusing to the surface of a-Se, which is well known to trap holes [80].…”

Section: Dos In the Vicinity Of Valence-band: Tof And Modelingmentioning

confidence: 99%

Charge transport in pure and stabilized amorphous selenium: re-examination of the density of states distribution in the mobility gap and the role of defects

Kasap

Koughia

Berashevich

et al. 2015

J Mater Sci: Mater Electron

View full text Add to dashboard Cite

We re-examine electron and hole transport in pure and stabilized amorphous selenium (a-Se) and attempt to construct a DOS distribution in the mobility gap below E c and above E v based on time-of-flight (TOF) transient photoconductivity measurements. First, we review the current status of a-Se, its recent use in commercial X-ray detectors, and the scientific information that is available in terms of its density of states (DOS). We review and describe a convenient multiple trapping transport mechanism to calculate the TOF transient photocurrents in a system with a distributed DOS in the mobility gap and invoke a number of assumptions that allow the photocurrent to be calculated as an inverse Laplace transform. The assumptions behind the model are critically examined. Then, by comparing the calculated TOF photocurrent shapes directly with experimental waveforms, the DOS distribution has been extracted in a-Se in the vicinity of conduction and valence bands (below E c and above E v ). Below the conduction band, the DOS distribution seems to demonstrate three peaks at around E c -0.30 eV, E c -0.45 eV and below E c -0.55 eV. First principles atomistic modeling provided insight into the origins of these peaks and the peaks have been assigned to certain valence-alteration pairs (VAPs) appearing in different configurations. In contrast to the conduction band vicinity, the DOS distribution above the valence band seems to be almost totally featureless. Within the range of experimental uncertainties, a featureless DOS below E v down to 0.55 eV seems to be able to explain a vast range of data, that is, it can explain hole transport not only as a function of the electric field and temperature down to 123 K, but also the thickness dependence of the mobility over two orders of magnitude. At room temperature, the hole transport is nondispersive but at temperatures below *200 K, it becomes dispersive exactly along the lines argued by Pfister and Scher (Adv Phys 27:747, 1978), and the mobility evinces a clear thickness dependence. The first principles calculations yield two defect levels related to VAP type defects in this region of the mobility gap but the valence band tail is so broad that it masks these peaks. This seeming asymmetry between the conduction and valence bands may be related to their physical origins: the conduction band arises from antibonding states and valence band is due to interacting lone pairs.

show abstract

Steady-state photoconductivity in amorphous selenium glasses

Cited by 15 publications

References 26 publications

Defect levels in the band gap of amorphous selenium

Defect levels in the band gap of amorphous selenium

Photocurrent measurements in chlorine‐doped amorphous selenium

Charge transport in pure and stabilized amorphous selenium: re-examination of the density of states distribution in the mobility gap and the role of defects

Contact Info

Product

Resources

About