GaN-based photocathodes with extremely high quantum efficiency

Uchiyama, Shota; Takagi, Yasufumi; Niigaki, Minoru; Kan, Hirofumi; Kondoh, Haruyasu

doi:10.1063/1.1883707

Cited by 95 publications

(52 citation statements)

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“…This requirement increases the complexity, mass, and volume of the spectrometer in such applications. The recent progress in high-quantum-efficiency GaN photocathodes 7 and systematic study of temporal emission response with hot carrier relaxation mechanisms involved in GaN photocathodes 8 has established IIInitride photocathodes as a promising candidate for UV low signal photodetection. The small electron affinity of GaN allows the development of highquantum-efficiency negative-electron-affinity (NEA) photocathodes with significant advantages such as solar blindness, radiation hardness, and low noise.…”

Section: Introductionmentioning

confidence: 99%

Novel Cs-Free GaN Photocathodes

Tripathi

Bell

Nikzad

et al. 2011

Journal of Elec Materi

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We report on a novel GaN photocathode structure that eliminates the use of Cs for photocathode activation. Development of such a photocathode structure promises reduced cost and complexity of the device, potentially with stable operation for a longer time. Device simulation studies suggest that deposition of Si delta-doped GaN on p-GaN templates induces sharp downward energy band bending at the surface, assisting in achieving effective negative electron affinity for GaN photocathodes without the use of Cs. A series of experiments has been performed to optimize the quality of the Si delta-doped layer to minimize the emission threshold of the device. This report includes significant observations relating the dependence of device properties such as emission threshold, quantum efficiency, and surface morphology on the Si incorporation in the Si delta-doped layer. An optimum Si incorporation has been observed to provide the minimum emission threshold of 4.1 eV for the discussed Cs-free GaN photocathodes. Photoemission (PE), atomic force microscopy (AFM), and secondary-ion mass spectroscopy (SIMS) have been performed to study the effect of growth conditions on device performance.

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Section: Introductionmentioning

confidence: 99%

Novel Cs-Free GaN Photocathodes

Tripathi

Bell

Nikzad

et al. 2011

Journal of Elec Materi

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“…So the excited electrons on the conduction band easily escape to vacuum. The QEs depend on the Mg doping concentration [8]. For the undoped GaN film the QE was only 0.15% at 4.4 eV.…”

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confidence: 98%

“…The bulb window was sapphire, and other fabrication details of the photo-tubes were the same as what we reported previously [8]. The PMTs were side-on type, have 9-stages circular-cage Cu-BeO dynodes, and quartz windows, respectively.…”

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confidence: 99%

“…Recently, we have realized extremely high QE for GaN-based photocathodes [8]. The spectral shapes of the response and the QE strongly depend on the Mg-doping concentration.…”

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confidence: 99%

“…From 200 to 700 nm region, spectral responses of the InGaN-based photocathodes were measured with the JASCO UV-25GD system [8]. Shorter than 200 nm region, we used an another measurement system consisted of a vacuum pump, a metal chamber, a deuterium lump, the monochromator with 1200 groove per mm ruled grating, slits, and shutters.…”

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Wide spectral responses In_xGa_1–xN deep UV photomultiplier tube

Uchiyama

Takagi

Kondoh

et al. 2007

Phys. Status Solidi (c)

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PACS 85.60.HaWe have designed and fabricated new photo-tubes and photomultiplier tubes (PMTs) using In x Ga 1-x N films as photocathodes. Longer spectral cutoffs were controlled with Indium compositions x, from 365 nm to 430 nm. The calibrated maximum quantum efficiency (QE) of 56% at 200 nm was achieved for x = 0.11 Indium composition in the photo-tubes. Sharp cutoffs at around 160 nms were determined by window materials and those at around 400 nms were determined by the band gaps of the photocathodes. Gain and input/output linearity properties were confirmed to be very good for the PMTs. 1 Introduction In these days, photocathode devices detecting in UV and blue spectral region are important for detection of scintillation and Cherenkov radiation in high-energy physics, like Kamiokande, and astrophysics experiments. Besides, researchers in space UV astrophysics and planetary require advanced detectors [1][2][3]. A high quantum efficiency (QE), a sharp cutoff, a low dark current, and large formats are important for these detectors. Because of a wide dynamic range, a low dark current, and being able to operate in single photon counting mode, GaN-based photocathodes are suitable for UV space missions.GaN-based photocathodes are being studied since 70's, some good results have been reported [4][5][6][7]. Recently, we have realized extremely high QE for GaN-based photocathodes [8]. The spectral shapes of the response and the QE strongly depend on the Mg-doping concentration. The calibrated QE of the GaN-based photocathode is maximized to be 71.9% at 230 nm by a Mg-doping concentration of 3.0 x 10 19 cm -3 . Within the frame work of the Spicer's three step model [9], the diffusion length and the escape probability were identified to be 150 nm, and 0.8, respectively.Recently, InGaN photocathodes are reported [1,10,11]. However, the relationship between the In composition of the InGaN films and the sharp cutoff or the QE is not clear. Then, we have designed and fabricated the InGaN photocathodes with high QEs, and have incorporated them into photomultiplier tubes (PMTs) with high gain and wide dynamic ranges.

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Novel Ultrabright and Air‐Stable Photocathodes Discovered from Machine Learning and Density Functional Theory Driven Screening

et al. 2021

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The high brightness, low emittance electron beams achieved in modern X‐ray free‐electron lasers (XFELs) have enabled powerful X‐ray imaging tools, allowing molecular systems to be imaged at picosecond time scales and sub‐nanometer length scales. One of the most promising directions for increasing the brightness of XFELs is through the development of novel photocathode materials. Whereas past efforts aimed at discovering photocathode materials have typically employed trial‐and‐error‐based iterative approaches, this work represents the first data‐driven screening for high brightness photocathode materials. Through screening over 74 000 semiconducting materials, a vast photocathode dataset is generated, resulting in statistically meaningful insights into the nature of high brightness photocathode materials. This screening results in a diverse list of photocathode materials that exhibit intrinsic emittances that are up to 4x lower than currently used photocathodes. In a second effort, multiobjective screening is employed to identify the family of M2O (M = Na, K, Rb) that exhibits photoemission properties that are comparable to the current state‐of‐the‐art photocathode materials, but with superior air stability. This family represents perhaps the first intrinsically bright, visible light photocathode materials that are resistant to reactions with oxygen, allowing for their transport and storage in dry air environments.

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GaN-based photocathodes with extremely high quantum efficiency

Cited by 95 publications

References 15 publications

Novel Cs-Free GaN Photocathodes

Novel Cs-Free GaN Photocathodes

Wide spectral responses In_xGa_1–xN deep UV photomultiplier tube

Novel Ultrabright and Air‐Stable Photocathodes Discovered from Machine Learning and Density Functional Theory Driven Screening

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GaN-based photocathodes with extremely high quantum efficiency

Cited by 95 publications

References 15 publications

Novel Cs-Free GaN Photocathodes

Novel Cs-Free GaN Photocathodes

Wide spectral responses InxGa1–xN deep UV photomultiplier tube

Novel Ultrabright and Air‐Stable Photocathodes Discovered from Machine Learning and Density Functional Theory Driven Screening

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Wide spectral responses In_xGa_1–xN deep UV photomultiplier tube