Measurement of Thermal Release and Transit Time in Case of Multiple Trapping

Abstract

The time-dependent current due to the drift of a small charge is investigated in an insulator with a single trap level. A theoretical study of multiple trapping gives the criteria to determine the transit time from the moment when the current is equal to 0.5 of its equilibrium value. A method to measure the thermal release time from the current relaxation which is due to charge ejection into the collecting electrode is proposed. The theoretical data are verified experimentally in high-polymeric vitreous selenium. om2. Die Ergebnisse bestatigen die Vorstellungen von der strukturellen Natur der Haftstellen, die die Driftbeweglichkeit beeinflussen. In1,roduc tionThe study of time-dependent flow of injected current in high-resistivity semiconductors can give valuable information on trapping centres. Many and Rakavy have numerically calculated trapping effects in case of transient space-chargelimited current and have found the latter useful to evaluate the time of carrier capture and that of thermal release [l]. For this purpose small-signal current transients are even more convenient : Blakney and Grunwald have obtained an explicit expression for the initial stage of current relaxation, limited to the condition that none of the drifting carriers reaches the collecting electrode [a, 31.Tefft has given the distribution functions of free and trapped charge for an arbitrary moment of time, and has derived some analytic approximations of time-dependent xerographic discharge [4].The correct measuring of the initia,l stage being difficult this paper proposes a useful analytic approximation for t'he last stage of current relaxation which is caused by ejecting previously multiple-trapped charge into the collecting electrode. The formulae obtained adequately describe the experimental data of high-polymeric vitreous selenium obtained from melt by rapid cooling. Evaporated amorphous selenium films hzve been repeatedly investigated [5 to 71. physic8 33/2

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

“…The original time-of-flight (TOF) transient photoconductivity measurements on a-Se date back to the sixties and seventies (some selected examples from this era are references [25][26][27][28][29][30][31] during which both hole and electron drift mobilities were carefully measured. A decade later, during the seventies and eighties, xerographic measurements, pioneered by researchers at Xerox, also became popular due essentially to the use of a-Se alloys in xerography.…”

Carrier Transport Processes in Amorphous Solids

“…This process was shown to be equivalent to conventional diffusion along the field direction [12][13][14], with the effective field-associated diffusion coefficient D f being proportional to the squared field strength as, Reasonably, the stronger the external electric field, the larger the typical variation of covered distances, given a fixed variation of trapping and release times.…”

Identifying Defects without a priori Knowledge in a Room-Temperature Semiconductor Detector Using Physics Inspired Machine Learning Model

“…The average trapping and detrapping times for holes were derived [ 11 ] using the average hole trapping time as measured in [ 12 , 13 , 14 , 15 , 16 ] using a statistical charge collection efficiency model based on known electron average trapping time. By direct comparison between measured and simulated signals at the cathode, average hole detrapping time is obtained [ 17 , 18 , 19 , 20 ]. The influence of deposition methods and type of metal contacts on trapping/recombination defects at the metal/semiconductor interfaces is studied in [ 21 ].…”