The sign of photocarriers and thermal quenching of photoconductivity in a-SiH

Recombination mechanisms in hydrogenated silicon nanocrystalline thin films

“…For a given light intensity, the photocurrent appears to decrease with increasing temperature and follows the relation I ph ∝ e Ea/kT , where E a is the photoconductivity activation energy [4,5]. This result is commonly observed in amorphous silicon films at temperatures above 100 K and has been explained in terms of a thermal-quenching effect in which valence band tail traps are converted to dangling bond recombination centers induced by temperature or light [6,7].…”

“…While the photocurrent generally increases with increasing temperature over a wide temperature range, a photocurrent decrease with increasing temperature is reported for some temperature regions. These results were explained in terms of a thermal quenching effect, in which valence band traps are converted to recombination centers under light illumination at some temperatures [4][5][6][7]. Metal contacts and the formation of metal silicide regions at the contact interfaces play an important role in determining these properties.…”

Simulation of hydrogenated amorphous silicon: temperature dependence of nonequilibrium distribution functions for trap states

“…That is extremely important for the argument of the temperature dependence of some physical phenomenon concerned with the electron density in the conduction band tail for a-Si:H. We study the temperature dependence of the NDF under photo illumination and zero bias voltage rigorously and find a new characteristic. Furthermore, we try to show that the new physical characteristic is applicable to the explanation of the temperature characteristic of the photoconductivity caused by the electron hopping [6][7][8][9] in the conduction band tail for a-Si:H. Figure 1 is the typical measured photoconductivity of a-Si:H for p-type, i-type, and n-type as a function of temperature [10,11]. In the area surrounded by broken line, the photoconductivity turns over from the increase to the decrease with increasing temperature: the temperature coefficient of the photoconductivity turns over from the positive to the negative.…”

“…This temperature characteristic of the photoconductivity is called the thermal quenching (TQ). Physical explanations of the TQ in a-Si:H have been reported by many researches [10][11][12][13][14][15][16][17][18][19][20][21]. Tran assumed that the recombination center changed from the VB tail to the dangling bond (DB) with increasing temperature, and the capture rate of the DB was larger than that of the VB tail.…”

“…Fig. 1 The typical measured photoconductivity in a-Si:H for p-type, i-type and n-type as a function of temperature [10,11]. In the area surrounded by broken line, the photoconductivity turns over from the increase to the decrease with increasing temperature.…”