Single-photon-induced random telegraph signal in a two-dimensional multiple-tunnel-junction array

A single-photon detection using a Si-based two-dimensional ͑2D͒ multiple-tunnel-junction field-effect transistor ͑FET͒ is reported. The single photon is detected as a random telegraph signal ͑RTS͒ in the single-hole-tunneling current regime. The frequency of RTS events depends on the light wavelength and intensity, indicating that the RTS occurs due to the single-photon absorption in the Si dots forming the 2D multijunctions. Based on a Monte Carlo simulation using an equivalent circuit representing the 2D multijunction FET, the " on " state of RTS appears when the photogenerated charge in the dot sensitively shifts the current level, while the on state returns to the " off " state when the charged dot is neutralized. The simulation result also shows that the RTS is triggered not only by the charging of a dot near the current percolation path, but also by the charging of a dot distances away from the path due to the nature of the multijunction system, i.e., the long screening length of the charge-induced potential. These results open up the development of single-photon devices with 2D multijunction systems.