In the case of diodes, the reverse recovery time
(trr) is the time required for a diode to switch from the forward direction to the reverse direction. During this time, the diode reaches the negatively biased operating conditions. Switching from the ON state to the OFF state takes a certain amount of time because the free charge carriers migrate to the corresponding region via the PN junction, electrons migrate towards the n-doped material, holes towards the p-region and recombine there. Since the charge carriers flow against the usual bias direction, the charge balance is called reverse recovery charge and the time is called reverse recovery time.