Features of carrier tunneling between the silicon valence band and metal in devices based on the Al/high-$K$-oxide/SiO$_{2}$/Si structure

The features of electron tunneling from or into the silicon valence band in a metal–insulator–semiconductor system with the HfO$_{2}$(ZrO$_{2}$)/SiO$_{2}$ double-layer insulator are theoretically analyzed for different modes. It is demonstrated that the valence-band current plays a less important role in structures with HfO$_{2}$(ZrO$_{2}$)/SiO$_{2}$ than in structures containing only silicon dioxide. In the case of a very wide-gap high-$K$ oxide ZrO$_2$, nonmonotonic behavior related to tunneling through the upper barrier is predicted for the valence–band–metal current component. The use of an insulator stack can offer certain advantages for some devices, including diodes, bipolar tunnel-emitter transistors, and resonant-tunneling diodes, along with the traditional use of high-$K$ insulators in a field-effect transistor.