Ultraviolet-enhanced photodiode employing n-ZnO/p-Si structure

We report on the photoelectric properties of $\mathrm{n-}\mathrm{ZnO}\mathrm{/p-}\mathrm{Si}$ photodiodes which detect UV photons in the depleted $\mathrm{n-}\mathrm{ZnO}$ and simultaneously detect visible photons in the depleted $\mathrm{p-}\mathrm{Si}.$ As characterized by $\mathrm{I–V}$ measurements in the photon range of 310 to 650 nm our photodiodes exposed to UV photons show a linear increase in photocurrent with reverse bias. In the visible range, the photocurrent rises rapidly with bias but saturates beyond a critical voltage. Our diodes exhibit strong responsivities of 0.5 and 0.3 A/W for UV (310-nm) and red (650-nm) photons, respectively, under a 30-V bias with a weak minimum near 380 nm, the wavelength corresponding to the band gap of ZnO. It is concluded that our $\mathrm{n-}\mathrm{ZnO}\mathrm{/p-}\mathrm{Si}$ diode can be a UV-enhanced photodiode that simultaneously detects UV and visible photons by employing two related photoelectric mechanisms in parallel.