Impact of In Situ Annealing on the Deep Levels in Ni‐Au/AlN/Si Metal–Insulator–Semiconductor Capacitors

Abstract

The impact of in situ annealing on the electrical properties of AlN/(111) p‐type silicon metal–insulator–semiconductor (MIS) capacitors is studied by capacitance–voltage (C–V) and deep‐level transient spectroscopy (DLTS). It is demonstrated that the in‐diffusion of Al leads to an enhanced free hole concentration close to the interface, which becomes more pronounced for the in situ annealed capacitors. This excess doping in the near‐surface region yields a strong capacitance freeze‐out above 200 K. At the same time, a higher density of near mid‐gap hole traps is found in the p‐type Si substrate. The fact that the deep‐level parameters (activation energy ET and hole capture cross section σp) change after annealing indicates that different types of Al‐related complexes or clusters are formed before and after in situ annealing. This is supported by the different trap filling kinetics observed in both cases: while for the as‐deposited samples exponential filling is found, typical for point defects, there is a tendency for logarithmic slow filling for the deep hole traps in the annealed capacitor.