Pn接合
これと電荷中性条件 N A x p = N D x n {\displaystyle N_{A}x_{p}=N_{D}x_{n}} より、空乏層の幅 W {\displaystyle W} は次のように得られる。
x p = 2 ε s q ( N A ′ N D ′ ( N A ′ + N D ′ ) ) V b i {\displaystyle x_{p}={\sqrt {{\frac {2\epsilon _{s}}{q}}\left({\frac {N'_{A}}{N'_{D}(N'_{A}+N'_{D})}}\right)V_{bi}}}}
x n = 2 ε s q ( N D ′ N A ′ ( N A ′ + N D ′ ) ) V b i {\displaystyle x_{n}={\sqrt {{\frac {2\epsilon _{s}}{q}}\left({\frac {N'_{D}}{N'_{A}(N'_{A}+N'_{D})}}\right)V_{bi}}}}
W = x p + x n = 2 ε s q ( N A ′ + N D ′ N A ′ N D ′ ) V b i {\displaystyle W=x_{p}+x_{n}={\sqrt {{\frac {2\epsilon _{s}}{q}}\left({\frac {N'_{A}+N'_{D}}{N'_{A}N'_{D}}}\right)V_{bi}}}}