Design and Growth of Visible-Blind and Solar-Blind III-N APDs on Sapphire Substrates

Ultraviolet (UV) studies in astronomy, cosmology, planetary studies, biological and medical applications often require precision detection of faint objects and in many cases require photon-counting detection. We present an overview of two approaches for achieving photon counting in the UV. The first approach involves UV enhancement of photon-counting silicon detectors, including electron multiplying charge-coupled devices and avalanche photodiodes. The approach used here employs molecular beam epitaxy for delta doping and superlattice doping for surface passivation and high UV quantum efficiency. Additional UV enhancements include antireflection (AR) and solar-blind UV bandpass coatings prepared by atomic layer deposition. Quantum efficiency (QE) measurements show QE > 50% in the 100–300 nm range for detectors with simple AR coatings, and QE ≅ 80% at ~206 nm has been shown when more complex AR coatings are used. The second approach is based on avalanche photodiodes in III-nitride materials with high QE and intrinsic solar blindness.

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“… Comparison of the spectral response of GaN and Al .4 Ga .6 N APDs. First published in Journal of Electronic Materials [ 52 ]. …”

Section: Figurementioning

confidence: 99%

Single Photon Counting UV Solar-Blind Detectors Using Silicon and III-Nitride Materials

Nikzad

Hoenk

Jewell

et al. 2016

Sensors

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“…Further, the avalanche gain is also estimated using a method described in [17], as follows:

A v a l a n c h e g a i n = \frac{I_{p d} - I_{d a r k}}{I_{p d_n o g a i n} - I_{d a r k_n o g a i n}}

where I pd is the photodiode current, I dark is the dark current and I pd_nogain and I dark_nogain are their average values at the unity-gain point. The avalanche gain achieved was about 10 at lower bias voltages, while increasing to 10 3 at 70 V, shown in Figure 12b.…”

Section: Measurement Resultsmentioning

confidence: 99%

A Hybrid Readout Solution for GaN-Based Detectors Using CMOS Technology

Hancock

Nikzad

Bell

et al. 2018

Sensors

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Gallium nitride (GaN) and its alloys are becoming preferred materials for ultraviolet (UV) detectors due to their wide bandgap and tailorable out-of-band cutoff from 3.4 eV to 6.2 eV. GaN based avalanche photodiodes (APDs) are particularly suitable for their high photon sensitivity and quantum efficiency in the UV region and for their inherent insensitivity to visible wavelengths. Challenges exist however for practical utilization. With growing interests in such photodetectors, hybrid readout solutions are becoming prevalent with CMOS technology being adopted for its maturity, scalability, and reliability. In this paper, we describe our approach to combine GaN APDs with a CMOS readout circuit, comprising of a linear array of 1 × 8 capacitive transimpedance amplifiers (CTIAs), implemented in a 0.35 µm high voltage CMOS technology. Further, we present a simple, yet sustainable circuit technique to allow operation of APDs under high reverse biases, up to ≈80 V with verified measurement results. The readout offers a conversion gain of 0.43 µV/e−, obtaining avalanche gains up to 103. Several parameters of the CTIA are discussed followed by a perspective on possible hybridization, exploiting the advantages of a 3D-stacked technology.

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“…Photoemissive detectors often possess low quantum efficiencies (< 30%) at UV wavelengths, require high-voltage operation, and are not suitable for use in magnetic fields. Wide-bandgap, visible-blind photodiodes have been demonstrated in materials systems like Al 1-x Ga x N and SiC, [1][2][3] with demonstrated QE's greater than 50%. 4 However, these devices are often performance-limited by materials quality issues, and are not commonly available in the large arrays needed for high resolution imaging and spectroscopy applications.…”

Section: Introductionmentioning

confidence: 99%

Materials and process development for the fabrication of far ultraviolet device-integrated filters for visible-blind Si sensors

et al. 2017

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In this work, we show that the direct integration of ultraviolet metal-dielectric filters with Si sensors can improve throughput over external filter approaches, and yield devices with UV quantum efficiencies greater than 50%, with rejection ratios of visible light greater than 10 3 . In order to achieve these efficiencies, two-dimensional doping methods are used to increase the UV sensitivity of back-illuminated Si sensors. Integrated filters are then deposited by a combination of Al evaporation and atomic layer deposition of dielectric spacer layers. At far UV wavelengths these filters require the use of non-absorbing dielectrics, and we have pursued the development of new atomic layer deposition processes for metal fluorides materials of MgF 2 , AlF 3 and LiF. The performance of the complete multilayer filters on Si photodiodes and CCD imaging sensors, and the design and fabrication challenges associated with this development are demonstrated. This includes the continued development of deep diffused silicon avalanche photodiodes designed to detect the fast 220 nm emission component of barium fluoride scintillation crystals, while optically rejecting a slower component at 300 nm.

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Design and Growth of Visible-Blind and Solar-Blind III-N APDs on Sapphire Substrates

Cited by 20 publications

References 13 publications

Single Photon Counting UV Solar-Blind Detectors Using Silicon and III-Nitride Materials

Single Photon Counting UV Solar-Blind Detectors Using Silicon and III-Nitride Materials

A Hybrid Readout Solution for GaN-Based Detectors Using CMOS Technology

Materials and process development for the fabrication of far ultraviolet device-integrated filters for visible-blind Si sensors

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