n-ZnO/p-Si UV photodetectors employing AlOx films for antireflection

We report on the antireflection property of AlOx film deposited on n-ZnO/p-Si photodiode and also report on the photoelectric properties of the diode fabricated for detecting both ultraviolet (UV) and visible photons. Optical reflectance spectra obtained from AlOx/ZnO/Si (100) samples exhibited that the reflectance in UV range over the bandgap of ZnO is lower than that in visible range below the bandgap. As characterized by current–voltage (I–V) measurements in the photon range of 310–670 nm, our photodiodes exposed to UV photons show a linear photocurrent increase with reverse bias while under visible photons the photocurrent rapidly rises but saturates from ∼5 V on. Our diodes exhibit 0.48 A/W of strong responsivity at 310 nm and 0.2 A/W at 670 nm under a reverse bias of 30 V but show weak responses near 380 nm which is the wavelength corresponding to the bandgap of ZnO.