AlGaN metal–semiconductor–metal photodiodes

Abstract

We report on the fabrication and characterization of AlGaN metal–semiconductor–metal photodiodes with sharp cutoff wavelengths from 365 to 310 nm. The detectors are visible blind, with an ultraviolet/visible contrast of about 4 orders of magnitude. The photocurrent scales linearly with optical power for photon energies both over and below the band gap, supporting the absence of photoconductive gain related to space-charge regions. No persistent photoconductivity effects have been detected. Time response is limited by the RC product of the measurement system, the transit time of the device being far below 10 ns. The normalized noise equivalent power at 28 V bias is lower than 17 pW/Hz1/2 in GaN detectors, and about 24 pW/Hz1/2 in Al0.25Ga0.75N photodiodes.

Effects of Bias on the Responsivity of GaN Metal–Semiconductor–Metal Photodiodes

“…2 shows the spectral response of GaN MSM photodiodes at 1 V and 5 V bias. The responsivity is quite flat over the bandgap, with a sharp cutoff wavelength that shifts to shorter wavelengths with increasing Al content [7]. A visible rejection of four to five orders of magnitude is obtained at 5 V, and the same behavior is observed for higher bias.…”

“…The recent demonstration of Al x Ga 1± ±x N photoconductors [1,2], p±i±n photodiodes [3], Schottky barrier photodetectors [4,5], and metal±semiconductor±metal (MSM) photodiodes [6,7] has confirmed that Al x Ga 1± ±x N alloy is the most promising semiconductor for visible-blind ultraviolet (UV) detection, in the range from 365 to 200 nm. MSM photodiodes present some advantages over other photovoltaic detectors, like their fabrication simplicity, low dark current, high bandwidth capability, and suitability for integration with field effect transistors.…”

Schottky Barrier Ultraviolet Photodetectors on Epitaxial Lateral Overgrown GaN

“…The cutoff wavelength of Al x Ga 1Àx N detectors can be tuned from 365 to 200 nm by changing the Al mole fraction of the alloy. AlGaN photoconductors [1,2], p±i±n photodiodes [3], Schottky barrier detectors [4,5] and metal±semiconductor±metal photodiodes [6] have recently been reported.…”

Interplay between GaN and AlN sublattices in wurtzite AlxGa1−xN alloys revealed by Raman spectroscopy

“…Good quality metal-semiconductormetal photodiodes were successfully fabricated on these samples. 6 Micro-Raman measurements have been performed in backscattering configuration at room temperature. An incident beam at 514.5 nm, well below the fundamental band gap of the material, was focused onto a region of ϳ1 m diameter, and the scattered light was analyzed through a Dilor triple spectrometer provided with a charge coupled device detector.…”