Photocurrent relaxation in pure and Pr-doped a-As₂S₃films

Abstract

Photocurrent relaxation was investigated in pure and Pr-doped amorphous As 2 S 3 films after constant illumination had been switched off. It is shown that, in the temperature range from 290 to 370 K and for the time interval 0.5-150 s, the photocurrent relaxation might be approximated as an algebraic function. An analytic model of the recombination-controlled photocurrent decay in amorphous semiconductors is formulated. For the As 2 S 3 samples with Pr impurity, the relaxation rate is lower and the form of the decay profile varies only lightly in comparison with non-doped samples. The results are discussed in terms of the band tails and deep acceptor-like centres present in a-As 2 S 3 films.

Optical absorption and photoconductivity of As 2 Se 3 :Sn AND Sb 2 Se 3 :Sn thin film structures

“…In "time-of-flight" experiments in amorphous As 2 Se 3 :Sn films it was also shown that the "optical bias" increase the drift mobility and decrease the recombination time [9]. In our case for explanation of the experimental results we have proposed an analytical model of the recombination-controlled photocurrent decay in amorphous semiconductors in terms of the band tails and deep acceptor-like centers [10]. Fig.3a shows the photoconductivity spectra measured on an alternating current for the amorphous films Sb 2 Se 3 and Sb 2 Se 3 : Sn x (x=0.01 and 0.5 at.…”

Effect of phase separation on the kinetics of photocurrent relaxation in Sn–Sb–Se glassy films

“…In these materials, the recombination time of carriers is the same as the carrier lifetime, when the free carrier density is more than the trapped carriers. Otherwise, the recombination process is dominated by the rate of trap emptying and is much larger than the carrier lifetime, resulting in the slow decay [9]. Persistent photocurrent increases with the increase in bias voltage and is found to be largest for the x = 10 film samples.…”

“…The increase in dark conductivity may also be the reason for the observed decrease in photosensitivity with composition and bias voltage conditions. Photocurrent relaxation in amorphous chalcogenides has gained a satisfactory interpretation in the framework of the model of multiple trapping in gap states, quasi-continuously distributed in the mobility gap of an amorphous semiconductor as proposed by Iovu et al [8,9]. The study of decay rates upon switching off the light source is more informative and revealing, especially in terms of relaxation processes prevailing in the system.…”

“…The study of decay rates upon switching off the light source is more informative and revealing, especially in terms of relaxation processes prevailing in the system. Non-exponential relaxation of photoconductivity is typical for the majority of amorphous semiconductors and is usually attributed to a wide spectrum of localized states in the gap [8][9][10][11][12]16]. It is generally assumed that, after light cessation, photocurrent decays due to the capture of non-equilibrium charge carriers (holes) by band tail localized states and, later on, due to recombination.…”

“…The effect of structural disorder is more on the conduction band as compared to the valence band; therefore, a larger number of electrons are trapped in localized states near to the conduction band [7]. Measurement of photoconductivity is an important tool for knowing the nature of recombination and defect states in the mobility gap of these semiconducting materials [8][9][10][11][12]. Importantly, photocurrent decay exhibits a stretched exponential function giving two important parameters, namely characteristic decay constant (τ ) and dispersion parameter (α), along with photosensitivity (S) and recombination parameter (γ ) which are useful in discussing the recombination processes in these materials.…”