Junction Potential Studies in Tunnel Diodes

A unique model is proposed for the potential distribution in the junction region of a tunnel diode. The essential feature of this model, in addition to band tailing, is a discontinuity in the band edges at the $n-p$ interface arising from a difference in the electron affinities of degenerate $n$- and $p$-type semiconductors. In connection with the proposed description of a tunnel diode junction, precise capacitance measurements have been carried out on a series of germanium units at 78°K. The experimentally determined values of the capacitance built-in voltage are in substantial agreement with the theoretical prediction, $e{V}_b=E_{g0\mathrm{}}+\frac{1}{5}({\xi }_n+{\xi }_p)$, and thus lend strong support to the validity of the discontinuity model. The temperature dependence of the built-in voltage is also discussed.