High performance Schottky UV detectors (265–100 nm) using n-Al0.5Ga0.5N on AlN epitaxial layer

Won

et al. 2017

Sensors

The UV-to-visible rejection ratio is one of the important figure of merits of GaN-based UV photodetectors. For cost-effectiveness and large-scale fabrication of GaN devices, we tried to grow a GaN epitaxial layer on silicon substrate with complicated buffer layers for a stress-release. It is known that the structure of the buffer layers affects the performance of devices fabricated on the GaN epitaxial layers. In this study, we show that the design of a buffer layer structure can make effect on the UV-to-visible rejection ratio of GaN UV photodetectors. The GaN photodetector fabricated on GaN-on-silicon substrate with a step-graded AlxGa−xN buffer layer has a highly-selective photoresponse at 365-nm wavelength. The UV-to-visible rejection ratio of the GaN UV photodetector with the step-graded AlxGa1−xN buffer layer was an order-of-magnitude higher than that of a photodetector with a conventional GaN/AlN multi buffer layer. The maximum photoresponsivity was as high as 5 × 10−2 A/W. This result implies that the design of buffer layer is important for photoresponse characteristics of GaN UV photodetectors as well as the crystal quality of the GaN epitaxial layers.

Section: Introductionmentioning

confidence: 99%

Selectively Enhanced UV-A Photoresponsivity of a GaN MSM UV Photodetector with a Step-Graded AlxGa1−xN Buffer Layer

Won

et al. 2017

Sensors

Applied Physics Letters

“…[6][7][8][9][10][11][12][13][14][15][16][17][18] In contrast to Al-rich AlGaN based p-i-n photodetectors, AlGaN Schottky barrier detectors are majority carrier devices, which do not face the challenging requirement of high quality p-type AlGaN layer for low resistance Ohmic contact formation. [6][7][8][9][10][11][12][13][14][15][16][17][18] In contrast to Al-rich AlGaN based p-i-n photodetectors, AlGaN Schottky barrier detectors are majority carrier devices, which do not face the challenging requirement of high quality p-type AlGaN layer for low resistance Ohmic contact formation.…”

mentioning

confidence: 99%

Hybrid AlN–SiC deep ultraviolet Schottky barrier photodetectors

Dahal

Tahtamouni

Fan

et al. 2007

Deep ultraviolet (DUV) Schottky barrier photodetectors have been demonstrated by exploiting the epitaxial growth of high quality AlN epilayer on n-type SiC substrate. The fabricated AlN∕n-SiC hybrid Schottky barrier detectors exhibited a peak responsivity at 200nm with very sharp cutoff wavelength at 210nm, very high reverse breakdown voltages (>200V), very low dark currents (about 10fA at a reverse bias of 50V), and high responsivity and DUV to UV/visible rejection ratio. These outstanding features are direct attributes of the fundamental material properties and high quality of AlN epilayers. The fabricated photodetectors also have a thermal energy limited detectivity at zero bias of about 1.0×1015cmHz1∕2W−1. These results demonstrated that AlN epilayers are an excellent candidate as an active material for DUV optoelectronic device applications.

“…Using a 50 Å Pd layer as a Schottky barrier on n-type GaN, Chen et al reported a responsivity of 0.18 A/W [3]. Our group has studied and characterized of GaN and AlGaN UV detectors on a sapphire substrate between the near VU and the SX region [5][6][7][8]. Our group has studied and characterized of GaN and AlGaN UV detectors on a sapphire substrate between the near VU and the SX region [5][6][7][8].…”

Section: Introductionmentioning

confidence: 97%

“…To overcome this problem, several groups have studied on GaN-and AlGaN-based UV detectors such as a photoconductor type [1], Schottky type [2][3][4][5][6][7][8], Schottky-based metal-semiconductor-metal type [9], and both p-n and p-i-n types [10]. For example, they are used in flame sensors and will be used in the future photolithography system, which will be available to a stepper with an excimer laser.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and characterization of UV Schottky detectors by using a freestanding GaN substrate

et al. 2004

GaN ultraviolet (UV) detectors were fabricated on a freestanding GaN substrate with low dislocation density. The resulting dark current density was below 1 nA/cm-2 at -8 V reverse bias, which was about 3 orders of magnitude lower than that of a similar detector made on a sapphire substrate. Moreover, the ideality factor was nearer to unity than the device on a sapphire substrate. In addition, by comparing the GaN-based device to a commonly used Si photodetector, we found that the GaN device had a lower signal-to-noise ratio and greater temperature stability. Therefore, we found a drastic reduction of dark current by using GaN freestanding substrates and so the GaN substrate produced a more effective detector than the sapphire substrate.