Abstract
We report observations of field emission from self-catalyzed GaAs nanowires grown on Si (111). The measurements were taken inside a scanning electron microscope chamber with a nano-controlled tungsten tip functioning as anode. Experimental data were analyzed in the framework of the Fowler-Nordheim theory. We demonstrate stable current up to 10−7 A emitted from the tip of single nanowire, with a field enhancement factor β of up to 112 at anode-cathode distance d = 350 nm. A linear dependence of β on the anode-cathode distance was found. We also show that the presence of a Ga catalyst droplet suppresses the emission of current from the nanowire tip. This allowed for the detection of field emission from the nanowire sidewalls, which occurred with a reduced field enhancement factor and stability. This study further extends GaAs technology to vacuum electronics applications.
Highlights
Field emission (FE), which is the quantum mechanical tunneling of electrons from the material surface through the vacuum energy barrier when a sufficiently high electric field is applied, can be exploited for several applications in vacuum electronics, such as flat panel displays [1,2], electron [3] and X-ray sources [4], and microwave devices [5]
Several one-dimensional (1D) and two-dimensional (2D) carbon-based nanostructures have been characterized as field emitters: Aligned carbon nanotube (CNT) films [6,7,8], single CNT [9,10], CNT networks [11,12,13], graphene [14,15,16], and graphene oxide nanosheets [17]
A interesting III–V nanomaterial system is comprised of self-catalyzed GaAs NWs grown by the vapor-liquid-solid method [29,30], allowing the direct integration of high quality GaAs structures on Si without the use of Au or other foreign catalyst metals, which would introduce deep level traps in Si [31]
Summary
Field emission (FE), which is the quantum mechanical tunneling of electrons from the material surface through the vacuum energy barrier when a sufficiently high electric field is applied, can be exploited for several applications in vacuum electronics, such as flat panel displays [1,2], electron [3] and X-ray sources [4], and microwave devices [5]. One-dimensional semiconductor nanostructures, such as nanowires (NWs), nanorods, nanoparticles, etc., have attracted considerable attention due to wide applicability for functional devices in the field of optoelectronics [18,19], photovoltaics [20,21], as well as vacuum electronics [22]. GaAs, which is one of the most popular III–V compound semiconductors with high electron mobility and direct band gap, in the form of nanowires (NWs) can have interesting properties for FE applications. A similar turn-on field (EON ≈2 V/μm) was measured in a parallel plate configuration (sample area 40 mm2) for aligned GaAs NWs fabricated via direct etching by an H plasma of the GaAs wafer covered with an Au film [36]. We report a stable emitted current from GaAs nanowires, with a field enhancement factor of up to β = 112 at anode-cathode separation of 350 nm for highly n-doped samples. Taking advantage of the suppression of field emission by Ga droplets on the NW tips, we report emission from the NW sidewalls, albeit with a lower field enhancement factor and with limited current stability
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