Q: How does the width of depletion region vary with change in doping of two regions?
Ans: As we have already discussed how depletion region is formed and now we know that depletion region is formed when recombining of electrons and holes occur. We discuss different cases as follow:
Doping of only p-type is greater: As doping of p type is greater and hence there would be more number of holes per unit area in p-type region and to recombine with electrons of n-type region we need the same number of holes. As we have the more density of holes and hence lesser region would provide enough number of holes and hence depletion width in the p-type would be lesser as shown below:
Doping of only n-type is greater: As doping of n type is greater and hence there would be more number of electrons per unit area in n-type region and to recombine with holes of p-type region we need the same number of electrons. As we have the more density of electrons and hence lesser region would provide enough number of electrons and hence depletion width in the n-type would be lesser as shown below:
Doping of both p-type & n-type is increased: As doping of both p-type & n-typeis greater and hence there would be more number of electrons per unit area in both regions and to develop same level of barrier we need the same number of electrons and holes. As we have the more density of electrons and holes hence lesser region would provide enough number of charge carriers and hence depletion width in the both p-type & n-typewould be lesser as shown below:
