In forward bias the electrons from n region move to p region after crossing the depletion region and holes from p region move to n region. But shouldn’t they recombine and hence the width of the depletion region width should remain constant? Why is it decreasing? And I read that the electrons that migrated to the p side now move to the positive terminal of the battery and vice versa for the holes on the n side. But how can they do so without recombining with majority carriers en route( since both the n and p sides outside the depletion region will have majority carriers)??
When you apply a forward bias voltage in a pn-junction, the width of the depletion region decreases because the applied voltage decreases the voltage drop corresponding to the built-in voltage of the pn-junction. In forward bias electrons will be injected from the n-region into the p-region and holes will be injected into the n-region, where they will flow as minority carrier diffusion currents. In thick p- and n-regions, they will recombine with the majority carriers there and the currents will continue gradually as majority carrier currents to the contacts. Majority holes reaching the contact recombine with electrons of the contact so that the eeltrical current continues as electron current in the contact. In short regions, the minority diffusion currents flow directly to the contacts. Holes recombine there again with the electrons of the contact. Depending on the semiconductor and recombination centers, recombination of electrons and holes can also occur already to a large part in the depletion region. This happens in typical Si pn-junctions.