Employing a multiband scattering formalism for ballistic tunneling currents, a systematic theoretical study of the current-voltage characteristics of metal-insulator and insulator-based resonant-tunneling diodes is presented. We predict ultrathin $\mathrm{metal}\left({\mathrm{CoSi}}_2\right)/\mathrm{insulator}\left({\mathrm{CaF}}_2\right)$ and $\mathrm{insulator}\left({\mathrm{CdF}}_2\right)/\mathrm{insulator}\left({\mathrm{CaF}}_2\right)$ heterostructures on silicon substrates to be excellent candidates for room-temperature quantum-effect devices. The scattering formalism in the framework of tight-binding theory is cast in a particularly compact and transparent form that is applicable to long-range tight-binding interactions and complex unit cells. The results are in good agreement with experimental data. The physical origin of the distinct current resonances, particularly in the metal/insulator structures, is explained in detail and found to originate in the localized character of the transition-metal d states. Furthermore, the stability of the resonance characteristics with regard to layer thickness variations, substrate orientations, and interface roughness is predicted.

• Received 16 February 2000

DOI:https://doi.org/10.1103/PhysRevB.62.7289