Tunnel diodes based on $n^{+}$-Ge/$p^{+}$-Si(001) epitaxial structures grown by the hot-wire chemical vapor deposition

$n^{+}$-Ge/$p^{+}$-Si(001) epitaxial structures are grown by hot-wire chemical vapor deposition from GeH$_4$ at a low substrate temperature ($\sim$325$^{\circ}$C). Prototype tunnel diodes allowing for monolithic integration into Si-based integrated circuits are formed based on these structures. Doping of the $n ^+$-Ge layers with a donor impurity (P) to a concentration of $>$ 1 $\times$ 10$^{19}$ cm$^{-3}$ is performed via the thermal decomposition of GaP. Distinct regions of the negative differential resistance are observed in the current–voltage characteristics of tunnel diodes.