Novel Cs-Free GaN Photocathodes

Tripathi, Neeraj; Bell, L. D.; Nikzad, Shouleh; Tungare, Mihir; Suvarna, Puneet; Sandvik, Fatemeh Shahedipour

doi:10.1007/s11664-010-1507-7

Cited by 16 publications

(3 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The bandgaps of the large-diameter nanowires were reduced to 2.40 and 0.74 eV, respectively, after the introduction of the n-type capping layer. Device simulation studies [15] have shown that deposition of an n-type doped layer on a p-GaN template induces downward band bending at the surface, contributing to an efficient negative electron affinity for GaN photocathodes without the use of Cs. Herein, we only analyze the total density of states (DOS) and partial density of states (PDOS) of GaN nanowires after covering with an n-type capping layer.…”

Section: Resultsmentioning

confidence: 99%

“…[ 13 ] These limitations of using cesium diminish the advantages offered by GaN material systems. Recently, work has been reported to achieve high quantum efficiency GaN photocathodes without cesiumization by using the n‐type capping layer, [ 14,15 ] as shown in Figure 1b. The built‐in field in the Ga‐polar (0001) growth direction [ 16 ] allows modification of the band structure inside the GaN material, leading to the design of photocathode devices.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electronic Behavior of GaN Nanowire Photocathode Surface Coated with n‐Type GaN Capping Layer via First Principles

Liu

Zhangyang

et al. 2022

Physica Rapid Research Ltrs

View full text Add to dashboard Cite

Conventional negative electron affinity photocathodes require alternate activation of Cs/O, and the instability of Cs makes the cathode surface easily inactive. A Cs‐free GaN photocathode structure is reported, in which band engineering of the photocathode surface induced by Si doping eliminates the need to use Cs for photocathode activation. This heterojunction structure can obtain a low‐barrier surface without activation. GaN nanowires with n‐type capping layers are established using first principles, and their stability, work function, and optoelectronic structures are analyzed. Si atoms replace Ga atoms more easily, thereby forming an n‐type capping layer. The formation energy of the n‐type capping layer of the nanowires surface is lower than that of the surface capping layer of the thin film. The addition of the n‐type capping layer reduces the work function of the GaN surface, which will help to enhance photoemission capability. The results clearly illustrate the positive effect of the n‐type capping layer on the electronic properties of the device, so this Cs‐free activation structure can be further considered.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electronic Behavior of GaN Nanowire Photocathode Surface Coated with n‐Type GaN Capping Layer via First Principles

Liu

Zhangyang

et al. 2022

Physica Rapid Research Ltrs

View full text Add to dashboard Cite

show abstract

“…The magnitude of polarization charge is dependent on the polar angle, with the largest out of plane polarization charge for c-plane III-nitrides [14]. Ga-polar p-type GaN photocathodes have previously been studied both with the use of a Cs-activation layer [15] and with novel Cs-free architectures employing a Si delta-doped surface layer [16]. The Si delta-doped layer and thin n+GaN cap required to stabilize the surface creates a narrow depletion region and increases downward surface band bending.…”

Section: The N-polar Gan Photocathode Structurementioning

confidence: 99%

Photoemission characterization of N-polar III-Nitride photocathodes as bright electron beam source for accelerator applications

Cultrera,

Rocco,

Shahedipour-Sandvik

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

We report on the growth and characterization of a new class of photocathode structures for application as electron sources to produce high brightness electron beams for accelerator applications. The sources are realized using III-Nitride materials and are designed to leverage the strong polarization field characteristic of this class material while grown in their wurtzite crystal structure to produce a negative electron affinity condition without the use of Cs, possibly allowing these materials to be operated in RF gun. A Quantum Efficiency (QE) of about 1x10 −3 and a Mean Transverse Energy (MTE) of electron of about 100 meV are measured at the operating wavelength of 265 nm. In a vacuum level of 3x10 −10 Torr the QE does not decrease after more than 24 hours of continuous operation. The lowest MTE, about 50 meV, is measured at 300 nm where the measured QE is 1.5x10 −5 . Surface characterizations reveal possible contribution to the MTE due to the surface morphology calling for more detailed studies.

show abstract

Digital Imaging for Planetary Exploration

Nikzad

Jewell

Carver

et al. 2015

Handbook of Digital Imaging

View full text Add to dashboard Cite

This chapter describes the history and current use of digital imaging in planetary remote and in situ exploration. The focus is mainly on visible as well as UV (ultraviolet) and near IR (infrared) imaging. We briefly discuss the operation of digital imagers, followed by the various readout schemes. We outline the requirements specific to planetary missions and review the history of planetary exploration through digital imaging. We examine the present and under‐planning instruments for remote sensing of planets. Finally, we discuss current trends in digital imaging and outline a possible path for future developments.

show abstract

Novel Cs-Free GaN Photocathodes

Cited by 16 publications

References 15 publications

Electronic Behavior of GaN Nanowire Photocathode Surface Coated with n‐Type GaN Capping Layer via First Principles

Electronic Behavior of GaN Nanowire Photocathode Surface Coated with n‐Type GaN Capping Layer via First Principles

Photoemission characterization of N-polar III-Nitride photocathodes as bright electron beam source for accelerator applications

Digital Imaging for Planetary Exploration

Contact Info

Product

Resources

About