Electrical characteristics of insulating aluminum nitride MIS nanostructures

Capacitance–voltage measurements of high quality PECVD and MBE grown aluminum nitride (AlN) thin films have been performed. The prepared films have shown polycrystalline (0 0 2)-preferential orientation, and were deposited on p-type Si (1 0 0) substrates with Pt forming the metal gate in a metal–insulator–semiconductor (MIS) configuration. The structure, crystallinity, texture and insulating properties have been found to depend on film thickness and were substantially influenced by the increase of the thickness. C–V measurements of the epitaxial and PECVD films were carried out and their insulating characteristics with increasing thickness (200–1000 nm) were investigated. The epitaxial films exhibited no hysteresis in capacitance behaviour, owing to better crystalline quality over the PECVD grown ones. Capacitance curves versus bias voltage have also been acquired at different temperatures; 10 K, 30 K and 50 K for deposited polycrystalline AlN films of (0 0 2) orientation. We have found that the defects trapped in the Pt/AlN/Si structure played a key role in dominating the overall behaviour of the C–V measurement curves. The trapped charges at the interface between the AlN insulating film and Si substrate caused the capacitance characteristics to shift to negative voltages, and the estimated charge density was of the order of 1010 and 108 cm−2 eV−1 for the PECVD and epitaxial samples respectively. The I–V measurements referred to space-charge conduction mechanism, and the deduced leakage current was found to be of the order of 10−9 A at 200 nm film thickness.