$12.$ A silicon p$-$n junction has acceptor concentration Na $=5$x$10\text{'}7$ cm on p$-$side and donor

concentration Na $=5$x$1015$ cm $3$ on n$-$side. Assume the intrinsic carrier concentration ni $=$ pi $=$

$1$x$101$ cm$-3$

$.$ What is the built$-$in contact potential Vo at $300$ K$?$ What is the width W of the

depletion region? What is the width of the depletion region under a reverse bias of $10$ V$?$