Observation of the resonance tunneling in field emission structures

Theoretical and experimental investigations of electron field emission from silicon-based resonance-tunneling layered structures have been performed. Numerical simulation of resonant and nonresonant field emission in Si-SiO2- Si*-SiO2 multilayer cathodes (MLCs) with quantum well (QWs) which takes int o account the tunneling process of electrons from the three-dimensional ele ctron density state of the emitter conductive band has;been carried out. Th e influence of the external electric field, temperature, MLC parameters and emitter doping on the resonant characteristics of the current was analyzed . Computer simulation has shown that the peak current density of MLCs with optimal thin barriers and sufficiently wide QW layers at a resonant value o f the electric field can sometimes exceed the current density of convention al cathodes. If the width of the QW is increased, the number of current res onant maxima (CRM) is multiplied. The CRM is shifted towards the lower elec tric field values and become more narrow if both the QW and the potential b arrier widths are increased. With temperature reduction the CRM becomes con trasted due to an increase in the electron impulse relaxation time and redi stribution of the electron state density in the emitter conduction band. Ex perimental multilayer structures with Si* delta-doped layer Si-SiO2-Si*-SiO 2, have been formed on silicon using low pressure chemical vapor deposition of ultrathin SiO2 and Si* films. In some cases the first ultrathin SiO2 la yer was grown on silicon with thermal oxidation. The multilayer structures were formed both on flat silicon wafers and on silicon tip arrays. Measurem ents of electron field emission into vacuum were performed in a diode (cath ode-anode) system. The resonant peaks of current density from MLCs have bee n observed experimentally for the first time. The value of these peaks is m ore than two times of that of the background curves. A comparison of experi mental and theoretical results has been performed to evaluate the fundament al parameters of the field emission resonance process. (C) 1999 American Va cuum Society. [S0734-211X(99)11302-7].