Metal-Polymer-Metal System in the High Static Electric Field

Abstract

Probably the first structure in which the negative differential resistance (NDR) effect has been observed was a tunnel diode [1]. The similar characteristic has been observed later in a metal-oxide--semiconductor tunnel junction [2] and then in the most artificial structures — multilayers [3]. The negative resistance phenomenon in multilayer stuctures can be easily understood in terms of the resonant tunneling [4]. In the case of a double barrier heterostructure (Fig. 1a) an electron tunneling transmission coefficient is enhanced when the energy of the tunneling electrons coincide with the bound state energy 1evel (Eb ) within the well (region II). While increasing the bias voltage, the bound' state energy level drops below the conduction band edge of region I. The electron must tunnel through the entire barrier structure to get the free states of region III in Fig. 1a giving rise to the drop in the current, so that I-V characteristic would show the negative resistance. The origin of the NDR effect in the tunneling diode and metal-oxide--semiconductor junction seems to be quite different. According to Zener's idea of the interband tunneling [5] the tunneling process in these junctions can occur between a filled band on the metal side to a next higher energy band on the semiconductor side by the application of the electric field (metal-oxide-semiconductor junction