SPECIAL FEATURES OF CURRENT - VOLTAGE CHARACTERISTICS OF DIODES MADE OF OVERCOMPENSATED SEMICONDUCTORS.

Study is made of the behavior of the current in diodes with thin and long bases made of semiconductors overcompensated with deep acceptors. Analytic expressions for the current - voltage characteristics of such diodes are obtained. It is found that, if the number of electrons occupying a recombination level is much smaller than unity, then the negative resistance region in the current - voltage characteristic of a long diode is followed by a region in which the voltage is practically independent of the current for a very wide range of currents. The mechanism which gives rise to the current - voltage characteristics of this type is explained. If deep acceptors are the only type of impurity in the base, the current - voltage characteristic of a long diode exhibits a vertical region of constant voltage and the negative-resistance region disappears. A study is also made of the mechanism which leads to a decrease in the differential photosensitivity of a phototransistor made of an overcompensated semiconductor, which occurs when the illumination level is increased. This is shown to be due to a decrease in the effective diffusion coefficient of nonequilibrium carriers, which is caused by an increase in the injection level. A comparison is made of the theoretical results with available experimental data.