Resonant electron tunneling in single quantum well heterostructure junction of electrodeposited metal semiconductor nanostructures using nuclear track filters

Abstract

We report on resonant electron tunneling through a Cu–Se heterostructure junction grown electrochemically in the submicron size pores (0.8 μm) of a nuclear track filter (Polycarbonate). The prominent feature of negative differential resistance (NDR) has been observed in the current–voltage (I–V) characteristic of the so-fabricated array of resonant tunneling diodes (RTDs) even at room temperature, along with a significant peak to valley current ratio (2.5) of the resonance. Tunneling structures of the nanofabricated RTDs around zero bias are also observed at room temperature. Our results show that the low cost and relatively easy electrodeposition method can be a very effective way to prepare resonant quantum tunneling devices, using the pores of nuclear track filters.

Introduction

The technological importance of Nuclear Track Filters (NTFs) is very large due to the various potential applications particularly in the field of micro/nanostructure electronic device fabrication. In recent years, there has been tremendous interest in nanopores and micropores in polymers, generated by swift heavy ions (SHI) due to a vast variety of applications [1], [2]. These pores are created by controlled chemical etching of ion-irradiated thin polymer foils, so as to produce NTFs. Physical properties of a material can change significantly in the transition between the macroscopic scale and the nanoscale. Therefore, nanophysics fabrication is very important both for its technological application and fundamental interest. The possibility of resonant tunneling in a zero-dimensional quantum well has been the subject of intense research over the years, since the first work by Reed et al. [3]. Functional devices based on resonant tunneling through double barrier heterostructures are of much promise in a variety of applications such as digital and analog circuits. However, a single barrier structure being easy to fabricate and of better high-frequency response is also of much interest. To date, most of the research on small area resonant tunneling devices has employed AlGaAs–GaAs heterostructure semiconducting material systems, which have been grown by Molecular Beam Epitaxy (MBE) technique followed by reactive ion etching [4], [5], [6]. Fabrication of resonant tunnel devices using the MBE technique has certain limitations as reactive ion etching can introduce damage at the device side wall surface [7]. However, recent advances in electrodeposition technique make possible the growth of well-defined periodic structures, such as magnetic multilayers with layer thicknesses as small as few nanometers [8]. Chakarvarti et al. [9], [10] recently employed this relatively easy and versatile electrodeposition technique to grow microstructure metal-semiconductor heterostructure junctions using the novel material system Cu–Se in the chemically etched pores of polycarbonate foils. The first and preliminary investigation on this entirely new and until now unpublished material system demonstrated characteristic feature for the formation of a microstructure resonant tunneling diode [10]. In this paper, we present results of our detailed investigation on the array of low-dimensional resonant tunneling diodes (RTD), fabricated by controlled electrodeposition of Cu–Se in the nanopores of a swift heavy ion-irradiated polycarbonate foil. We also demonstrate a low-cost resonant tunneling device as a result of a metal semiconductor (Cu–Se) single barrier heterostructure, which provides negative differential resistance (NDR) characteristic with high peak to valley current ratio (PVR) even at room temperature.