Dielectric properties of AlN film on Si substrate

AlN films were deposited on p-Si(1 1 1) substrates by a low-pressure metal–organic chemical vapor deposition (MOCVD) system and an Al–AlN–Si (MIS) capacitor was then prepared with the AlN layer as the insulator. With the capacitance–voltage (C–V) curves of Al–AlN–Si capacitors measured at 50 Hz–10 MHz, we found the frequency dependence of the capacitance of the accumulation region, that is, the capacitance of the AlN layer. It is observed that the relative dielectric constant (er) of AlN declined from 20.7 to 1.2 with increasing frequency. The peak of dielectric loss tangent (tan δ) was observed at a frequency of 1.5 MHz. With the Debye equation and the Cole–Cole empirical formula, the relaxation time (τ) was fitted to be about 10−7 s. From these results and works of others, it was concluded that this dielectric behavior was caused by dipolar relaxation relating to N vacancies in the AlN layer.