Type conversion in irradiated silicon diodes

We have observed conversion from $p$ - to $n$ -type of the base layer of $\mathrm{n+\backslash p\backslash p+}$ silicon diodes irradiated with more than roughly ${\text{5×10}}^{16}\hspace{0.17em}{\mathrm{cm}}^{\text{−2}}$ 1 MeV electrons. Annealing for 15 min at 200 °C results in a recovery of $p$ -type conduction in diodes in which type conversion had been induced. Solar cells which employ the same diode structure are severely degraded by irradiation with more than ${10}^{16}\hspace{0.17em}{\mathrm{cm}}^{\text{−2}}$ 1 MeV electrons and show only a weak infrared response after irradiation with ${10}^{17}\hspace{0.17em}{\mathrm{cm}}^{\text{−2}}$ 1 MeV electrons, consistent with the creation of an $\mathrm{n+\backslash n\backslash p}$ structure due to type conversion.