Differential capacitance of a $p^+$–$p$ junction

The differential capacitance of a $p^+$–$p$ junction formed by charge redistribution near the junction, has been investigated taking into account the electric field in the quasi-neutral $p$ region. The dependence of the capacitance and current of the $p^+$–$p$ junction on its voltage is obtained. It is shown that a change in the sign of the $p^+$–$p$-junction capacitance with an increase in the injection level is caused by a decrease in the bipolar drift mobility in the $p$-type region. It is also demonstrated that a change in the sign of the $p^+$–$p$-junction capacitance with an increase in the reverse voltage determines the charge reduction near the junction, as the increase in the negative charge of acceptor ions predominates over the increase in the positive charge of holes.