Reverse Biased P-N Junction:
When battery connections to the semiconductor are made as p type is connected with negative battery terminal and n type is connected with positive terminal the junction is said to be reverse biased. In this case holes are attracted by the negative battery terminal and electrons by the positive terminal so that both holes and electrons move away feom the junction and away from each other. Since there is no electron-hole combination, no current flows and the junction offers a high resistance.
Another way of looking at the process is that, in this case, the applied voltage increases the barrier potential thereby blocking the flow of majority carrier.
Incidentally, it may be noted that under reverse bias conditions, width of depletion layer is increased because majority charge carriers are pulled away from the junction.It also increases the potential barrier.