A PN junction is in series with 100 ohms resistor PN junction is basically a diode. The circuit is shown below
Forward current through diode is 100 mA.
When the voltage is reversed the PN junction is switched from conduction state. It needs same time to return to non- conduction state, so the PN junction behaves as a short circuit for the little time even in reverse direction.
This is due to accumulation of stored access minority charge when diode is forward biased so, the current will be –100 mA.