Light-Induced Effects on Photocurrent Transients

The most unique and intriguing features of chalcogenide vitreous semiconductors are the photoinduced changes appearing as a nearly parallel shift of the optical absorption edge to lower energy (so-called photodarkening effect) after irradiation 

Let us first consider the results of TOP measurements on Se-rich amorphous chal-cogenides [8]. 

At room temperature, the amorphous Se (a-Se) films exhibit very slight but definite photodarkening. The effect consists of a decrease of transmission (—2% in magnitude) after illumination, which was spontaneously restored as excitation was switched off It was found that the restoration period increases with the arsenic concentration. In other words, the photoinduced changes are transient (dynamic) and not permanent. 

As alloying results in decreasing both the electron and hole mobility and 

T = 293 K) data 1, dark rested data 2, exposed data 3, 4, 5, and 6, exposed and then dark rested for 5, 10, 50, and 160min, respectively. 

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