2 ∕ 3 in. ultrahigh-sensitivity image sensor with active-matrix high-efficiency electron emission device

Abstract

A 640×480pixel image sensor has been developed for low light imaging with a practical resolution. This image sensor combined an active-matrix high-efficiency electron emission device (HEED) with a high-gain avalanche rushing amorphous photoconductor (HARP) target. To meet the requirement for a scaling of the imaging size, we developed a 2∕3in. image sensor based on an active-matrix HEED with 13.75×13.75μm2pixels. The highly emissive property of 3.8μA∕pixel was comparable to that obtained previously from a 1in. device. The possible effect of the pixel size scaling on the image-pickup sensitivity was compensated by a significant increase in the emission current density. The technological potential of the HEED-HARP image sensing has been further enhanced toward practical use.

Highly Monochromatic Electron Emission from Graphene/Hexagonal Boron Nitride/Si Heterostructure

“…Planar metal-oxide-semiconductor (MOS) electron emission devices − have excellent attributes, such as a low driving voltage, they function at low , and atmospheric pressures , and in liquids, − and have a low divergence angle for the electron beam . Several practical applications have been proposed, including in field emission displays, , in highly sensitive image sensors, − and for electron beam lithography systems. − The electron emission source plays a critical role in the performance of electron microscopy setups, such as scanning electron microscopes (SEM), transmission electron microscopes (TEM), and electron beam lithography. Compared with Schottky-type electron sources and tungsten field emitters, MOS-type electron emission devices are disadvantaged by their broad emitted electron energy spread.…”

High quantum efficiency UV detection using a‐Se based photodetector

“…It should be noted that no blocking layer is deposited on or beneath the a‐Se film in this study: these blocking layers are reported to prevent carrier injection into the a‐Se film, which prevents dark current and enables one to apply a high voltage across the film 7–9. The carrier multiplication without blocking layers may be explained by the diode‐structured device using a cold cathode: since the present device is driven by a cold cathode, the emission current is negligibly small unless the potential difference between the anode and the cathode is smaller than the extraction voltage of the cold cathode.…”

“…This thermal treatment helps the a‐Se structure shift into a quasi‐stable state: such samples typically have stable current−voltage characteristics and are generally more resilient to thermal degradation. It should be noted that no blocking layers are deposited on or beneath the a‐Se film, despite the previous reports on carrier multiplication 7–9.…”

“…Amorphous selenium (a‐Se) is a promising material for a high‐sensitivity photodetector that has low thermal noise and wide detectable wavelength range that covers the visible to UV 5, as well as X‐ray 6 regions. The high sensitivity of an a‐Se‐based photodetector is explained by signal enhancement due to an internal carrier multiplication: this effect leads to a quantum efficiency of greater than 100% 7–9, meaning that more than one carrier is generated per incident photon. Although this carrier multiplication has long been treated as a mystery in solid‐state physics, we have recently demonstrated this phenomenon in detecting visible light, and proposed a way to evaluate its quantum efficiency 10.…”

Electron Optical Properties of Microcolumn with Field Emitter

“…Field emitter arrays (FEAs) with focusing electrodes are promising devices for applications such as electron beam lithography, [1][2][3][4][5] high-definition field emission displays, [6][7][8][9][10][11] and image sensors. [12][13][14][15][16] Our group has previously investigated the fabrication processes and focusing characteristics of four-and five-gated FEAs. 17,18) Crossover of an electron beam was realized using a multi-gated FEA without any external optical system.…”