N-ZnO/p-Si UV photodetectors employing AlO x films for antireflection

Abstract

We report on the antireflection property of AlO x 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 AlO x /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.