Question

why is the width of depletion region in reverse is more than that of forward biasing

Answer 1

Forward Biasing:

When P type of semiconductor is connected to positive pole of battery and N type to negative pole, free electron from N region are attracted by holes of P region. This results in the flow of current through the diode. Due to the flow of current the width of depletion layer is small.

Reverse Biasing:

When P type of semiconductor is connected to negative pole of battery and N type to positive pole, free electron from N region are not attracted by holes of P region. Due to this diode doesn't conduct and barrier potential is developed across the junction. This increases width of depletion layer across the junction.