Polycrystalline AlN films deposited at low temperature for selective UV detectors

Abstract

Polycrystalline aluminum nitride (AlN) thin films were fabricated at 300°C by two different operating modes of magnetron reactive sputtering (RMS) method: radio-frequency (rf) and direct current (dc) RMS. The films obtained by the rf RMS are highly textured with (0 0 0 1) orientation and have columnar structure, and the films fabricated by the dc RMS have fibrous structure with crystallites oriented in ( 1 0 1 ̄ 0 ) and ( 1 1 2 ̄ 0 ) plans. Both types of AlN films are sensitive to UV radiation and the photo-conductivity decreases rapidly with increasing wavelength (by more than four orders of magnitude from 200 to 400 nm). The optical and electrical properties of both types of films are comparable, but the columnar grain structure of the first type may lead to enhanced dark currents in sandwich structure devices, so that the second type of films seems to be more appropriate for this kind of devices.