Electroluminescence of diamond NV centers at temperatures 450$^\circ$C–680$^\circ$C

The electroluminescence spectra are investigated of a diamond light-emitting $p$–$i$–$n$ diode based on a nitrogen-doped synthetic diamond single crystal ($n$-type of conductivity) grown at high pressure and temperature, and thin diamond $i$-layer grown by homoepitaxial growth from a gas phase with a nitrogen concentration of 10$^{14}$–10$^{15}$ cm$^{-3}$ with nitrogen-vacancy and silicon vacancy optically active centers, and a layer highly doped with boron ($p$-type of conductivity). To increase the concentration of luminescence centers, the diode was irradiated with an electron beam with energy 3 MeV at a dose of 5 $\cdot$ 10$^{17}$ cm$^{-2}$, followed by annealing at $T$ = 800$^\circ$C in vacuum for 2 hours. The electroluminescence spectra were measured at temperatures in the range 450$^\circ$C–680$^\circ$C both before and after electron irradiation. Before electron irradiation, the maximum of the electroluminescence band was observed in the wavelength range of 610–680 nm, depending on the temperature, bias, and current of the diode; and after electron irradiation and annealing, at a wavelength of 680 nm at $T$ = 575$^\circ$C–600$^\circ$C. The maximum integral brightness of the radiation from nitrogen vacancy centers $\sim$ 10$^{12}$ photon/s was observed at $T$ = 575$^\circ$C after electron irradiation and annealing.