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Cadmium selenide TFT's operated at fixed gate and drain bias show a slow decay of the drain current. The time dependence of this decay was found to be logarithmic. Below room temperature the rate of decrease of the number of charge carriers in the surface-channel depends only weakly on both temperature and gate bias. These results can be described with a model in which tunnelling of electrons from the channel to traps in the oxide forming the gate insulation is assumed. As time proceeds the traps are filled by this process to an ever-increasing depth. Somewhat above room temperature a strong drift of a different nature occurs. In contrast to the low temperature drift, which can be suppressed by suitable treatment, this type of drift could not be removed. It presents a serious drawback to practical applications of the CdSe TFT. In several respects the TFT's used in this investigation differ from the conventional type. Their construction is briefly discussed.

The p-n-junction photovoltaic effect in Zn-doped GaP was studied as a function of various parameters. The spectral sensitivity, the temperature dependence of the short-circuit current and the open-circuit voltage are discussed. In addition to the intrinsic effect an extrinsic photovoltaic effect was found. Arguments are given to show that the extrinsic response is not an electrode effect, but is clearly correlated with the specific dope introduced into the GaP bulk.