Wide spectral responses In_xGa_1–xN deep UV photomultiplier tube

Abstract

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.

Characterization of an InGaN-based photo-emissive device

“…Previous work on InGaN photocathodes has demonstrated promising photocathode behavior [3][4][5][6] in reflection mode measurements. Reflection mode measurements refer to the fact that the incident light illuminates the same surface from which electrons are emitted.…”

Improvement of Cutoff Characteristics for In0.11Ga0.89N-Based Photocathodes Using Light-Emitting Diode Real Time Spectral Sensitivity Monitoring System

“…[6][7][8] Furthermore, GaN and In x Ga 1Àx Nbased photocathodes with high sensitivities have been investigated. 9,10) Photomultiplier tubes (PMTs) with GaN or In x Ga 1Àx Nbased photocathodes are very useful detectors for sensing only weak UV lights under visible light environments. To detect only UV light, it is necessary for GaN or In x Ga 1Àx Nbased photocathodes to have two important properties; high QEs in the UV region and sharp cutoff characteristics between the UV and the visible region.…”

“…The In composition x ¼ 0:11 was selected to realize the photoemission cutoff wavelength at around 400 nm as same as our former report. 10) The In 0:11 Ga 0:89 N films were incorporated in cylindershaped photo-tubes to operate in reflection-mode. The bulb tube windows were quartz, and other fabrication and surface treatment details of the PMTs were the same as what we reported previously.…”

“…The bulb tube windows were quartz, and other fabrication and surface treatment details of the PMTs were the same as what we reported previously. 9,10) The monitoring system consists of the LEDs as light sources, and electric meters with amplifiers. The LED's peak wavelength were 285 nm (UVTOP UVTOP280TO39HS), 375 nm (Nitride Semiconductors, NS375L-ERLM), and 470 nm (Nichia NSPB500S), respectively.…”

Algorithm for in vitro Sun Protection Factor Based on Transmission Spectrum Measurement with Concomitant Evaluation of Photostability

“…1). The quantum efficiency of the new UV photomultiplier tube (PMT) was calculated according to the reported method (12,13). A xenon lamp equipped with WG 320 (thickness 1 mm, Schott) and UG 11 (thickness 1 mm, Schott) filters was used as a UV light source for the solar simulator.…”