Enhanced recombination tunneling in GaAs pn junctions containing low-temperature-grown-GaAs and ErAs layers

We report electrical conductivity studies of highly-doped GaAs $\mathrm{pn}$ diodes containing a strongly $n$ -doped low-temperature-grown (LT)–GaAs layer and $\mathrm{pn}$ junctions containing an approximately one monolayer thick ErAs layer. At room temperature, current densities of 1 ${\mathrm{kA/cm}}^2$ for the $n$ -LT–GaAs samples and ${\mathrm{6\hspace{0.5em}kA/cm}}^2$ for the ErAs samples at 1 V forward bias have been measured. The $\mathrm{I–V}$ characteristics under forward bias for the $n$ -LT–GaAs and ErAs samples exhibit significantly different behavior. At low temperatures, the $n$ -LT–GaAs samples reveal a shoulder in the $\mathrm{I–V}$ characteristics, which can be explained by a model taking into account tunneling of carriers into LT midgap states. A similar model was able to explain the current transport in the ErAs diodes as tunneling of carriers into metallic regions inside the $\mathrm{pn}$ junction.