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Low-cost digital system for photoinduced transient spectroscopy

A low-cost, easy to construct, digital system for measurement of photocurrent transients in semi-insulating materials is described. The hardware and software involved are detailed. In order to improve the signal-to-noise ratio, an automatic dark current cancellation circuit was introduced using a D/A converter and the software controlled the change of amplifier gain. Typical photocurrent transient data obtained with this system for semi-insulating GaAs samples are presented.