Figure 1: Single-photon sources in fully fabricated p⁺n junction diodes in 4H–SiC.

(a) Schematic of the confocal setup used to characterize the single-photon emitters. It includes a Hanbury Brown and Twiss interferometer with two single-photon avalanche detectors (D1 and D2) connected to a correlation card (CC). The dichroic mirror (DM) was removed when in used in EL mode. A partial schematic of the device consisting of a p⁺ top contact is also shown. Three floating guard rings encircle the central contact to decrease the electric field at the main contacted junction. (b) I–V-curve of the diode. In this device, features due to shunt resistance, tunnelling current, diffusion current and series resistance are indicated by the letters a–d, respectively. (c) EL map of the edge region of a device. Scale bar, 1 μm. (d) Room temperature EL spectrum showing the source of the background (D₁ line) and the single-photon emitter with a ZPL at 745 nm and a broad phonon side-band. (e) Background corrected anti-bunching traces with g⁽²⁾(τ=0)<0.1 indicating excellent single-photon emission characteristics. The detector count rates were N₁≈N₂=160 k.c.p.s. with ρ=0.82, a total integration time of 20 min and a bin width of 64 ps.