Browsing by Subject "Photodiode"

Now showing 1 - 9 of 9

Open Access
AlxGa1-xN based solar blind Schottky photodiodes
(2004) Tut, Turgut
Photodetectors are essential components of optoelectronic integrated circuits and fiber optic communication systems. AlxGa1−xN is a promising material for optoelectronics and electronics. Applications include blue and green LEDs, blue laser diodes, high power-high frequency electronics, and UV photodetectors. Photodetectors that operate only in the λ < 280 nm spectrum are called solarblind detectors due to their blindness to solar radiation within the atmosphere. In this thesis, we present our efforts for the design, fabrication and characterization of Al0.38Ga62N/GaN based solar blind Schottky photodiodes. We obtained very low dark current, high quantum efficiency, high detectivity performance. Under 25 V reverse bias, we measured a maximum quantum efficiency of 71 percent at 254 nm and a maximum responsivity of 0.15 A/W at 253 nm for a 150 micron diameter device. To our knowledge, these are the best values reported in the literature. For a 30 micron device, 50 ps FWHM pulse response is observed. When the scope response is deconvoluted, a maximum 3-dB bandwidth of 4.0 GHz is obtained for 30 micron diameter Schottky photodiodes.
Open Access
Design, fabrication and characterization of high performance resonant cavity enhanced photodetectors
(1998) Bıyıklı, Necmi
Photodetectors are essential components of optoelectronic integrated circuits and fiber optic communication systems. For higher system performances, photoreceivers with high bandwidth-efficiency products are needed. A new family of photodetectors introduced in the early 90's offers high performance detection along with wavelength selectivity: resonant cavity enhanced (RCE) photodetectors. In this thesis, we present our efforts for the design, fabrication and characterization of AlGaAs/GaAs-based Schottky and p-i-n type RCE photodiodes operating within the first optical communication window. Epitaxial wafers are designed using scattering matrix method based simulations and grown with molecular beam epitaxy. Schottky photodiode was primarily designed for high-speed operation, where as in p-i-n structure we aim to achieve near unity quantum efficiency. Measurement results show reasonable agreement our theoretical simulations. Fabricated Schottky and p-i-n RCE photodiode samples demonstrated high bandwidth-efficiency products, 36 and 46 GHz respectively. These results indicate the best performances for RCE Schottky and p-i-n photodiodes reported in scientific literature.
Open Access
Fabrication and characterization of high-speed, high quantum efficiency, resonant cavity enhanced Schottky photodiodes
(1998) Ata, Erhan Polatkan
Rapidly developing “photonics” technology promises higher bcindwidths of communiccition than any other techniciue did ever. The increasing rate of communication not only alters science and technology, but brings a global cultural exchange, which seems to be one of the most important revolutions in the history. Photodetectors, as vital corniDonents of optoelectronics, cire still being developed to achieve satisfying performances for the increasing communication demcinds. We have designed and fabricated high-speed, high efficiency resonant Ccivity enhanced (RCE) Schottky photodiodes, suitable for 800-850 mil operation wavelengths. We have used two different GaAs/AlGaAs based epitaxial structures to achieve high performance. From one of these structures, we fabricated photodiodes with 50% quantum efficiency and 80 GHz 3-dB bandwidth. The other structure had a design suitable for préfabrication wavelength tuning and adjustable active layer thickness. On this structure, we achieved 20% quantum efficiency along with, world record for RGB photodiodes, over 110 (Hlz 3-dB estimated bandwidth. We investigated effects of active layer, top Au layer, and silicon nitride coating layer thicknesses on the RCE devices. Discrepancy between theory and experiments were also explained briefly. Methods for improving performances of photodiodes has been proposed ¿is possible future work. Possible appliccitions, which may make use of current knowhow on the subject, have also been mentioned.
Open Access
The growth, fabrication and characterization of high performance AI(formula)Ga(formula)N metal-semiconductor-metal photodiodes
(2006) Bütün, Serkan
High performance UV photodetectors have attracted unwarranted attention for various applications, such as in military, telecommunication, and biological imaging, as an AlxGa1-xN material system is also rather suitable for such applications. Its direct band gap covers the spectrum from 200 nm to 360 nm by way of changing the Al concentration in the compound. In this present thesis, the design and growth of an Al0.75Ga0.25N template on sapphire substrate and a deep-UV photodiode with a cut off wavelength of 229 nm that was fabricated on the Al0.75Ga0.25N template is presented. A responsivity of 0.53 A/W was attained corresponding to a detectivity of 1.64 × 1012 cmHz 1/2/W at a 50 V bias and 222 nm UV light illumination. The UV/VIS rejection ratio of seven orders of magnitude was achieved from the fabricated devices. The second work that was conducted in this thesis was the growth of a semiinsulating (SI-) GaN template. We also fabricated visible-blind photodetectors on this semi-insulating (SI-) GaN template. Furthermore, we fabricated identical samples on a regular GaN template in order to investigate any possible i improvement. The improvement found was obvious in terms of dark current. A dark current density of 1.96 × 10-10 A/cm2 at a 50 V bias voltage for an SI-GaN photodetector was obtained, which is four orders of magnitude lower than devices on a regular GaN template. Devices on an SI-GaN had very high detectivity, and therefore, SI-GaN was used for low level power detection. The photogenerated current was well above the dark current that was under the illumination of just a few picowatts of UV light.
Open Access
High-efficiency p-i-n photodetectors on selective-area-grown Ge for monolithic integration
(Institute of Electrical and Electronics Engineers, 2009) Yu, H.-Y.; Ren, S.; Jung, W. S.; Okyay, Ali Kemal; Miller, D. A. B.; Saraswat, K. C.
We demonstrate normal incidence p-i-n photodiodes on selective-area-grown Ge using multiple hydrogen annealing for heteroepitaxy for the purpose of monolithic integration. An enhanced efficiency in the near-infrared regime and the absorption edge shifting to longer wavelength is achieved due to 0.14% residual tensile strain in the selective-area-grown Ge. The responsivities at 1.48, 1.525, and 1.55 μ are 0.8, 0.7, and 0.64 A/W, respectively, without an optimal antireflection coating. These results are promising toward monolithically integrated on-chip optical links and in telecommunications. © 2009 IEEE.
Open Access
High-performance AlxGA1-xN-Based UV photodetectors for visible/solar-blind applications
(2004) Bıyıklı, Necmi
High-performance detection of ultraviolet (UV) radiation is of great importance for a wide range of applications including flame sensing, environmental (ozone layer) monitoring, detection of biological/chemical agents, missile early warning systems, and secure intersatellite communication systems. These applications require high-performance UV photodetectors with low dark current, high responsivity, high detectivity, and fast time response. The widebandgap AlxGa1−xN ternary alloy is well-suited as a photodetector material for operation in the wavelength range of 200 nm to 365 nm. Its outstanding material properties (direct bandgap, tunable cut-off, allows heterostructures, intrinsically solar-blind) make AlxGa1−xN suitable for a variety of harsh environments. If properly constructed, AlxGa1−xN-based photodetectors could offer significant advantages over the older photomultiplier tube (PMT) technology in terms of size, cost, robustness, complexity, dark current, bandwidth, and solar-blind operation. The motivation behind this work is the need for high-performance, solid-state UV photodetectors that can be cost-effectively manufactured into high-density arrays. We have designed, fabricated, and characterized several visible/solar-blind AlxGa1−xN photodiode samples. With solar-blind AlxGa1−xN photodiode samples, we achieved excellent device performance in almost all aspects. Very low dark currents were measured with heterostructure AlxGa1−xN Schottky and p-i-n samples. The extremely low leakage characteristics resulted in record detectivity and noise performance. Detectivity performance comparable to PMT detectivity was achieved. True solar-blind operation (sub-280 nm cut-off) with high visible rejection was demonstrated. In addition, we improved the bandwidth performance of AlxGa1−xN-based solar-blind photodetectors by over an order of magnitude. Solar-blind Schottky, p-i-n, and metal-semiconductor-metal photodiode samples exhibited very fast pulse response with multi-GHz bandwidths.
Open Access
High-speed visible-blind GaN-based ITO-Schottky photodiodes
(SPIE, 2002) Bıyıklı, Necmi; Kimukin, İbrahim; Kartaloğlu, Tolga; Aytür, Orhan; Özbay, Ekmel
In this paper we present our efforts on the design, fabrication and characterization of high-speed, visible-blind, GaN-based ultra-violet (UV) photodiodes using indium-tin-oxide (ITO) Schottky contacts. ITO is known as a transparent conducting material for the visible and near infrared part of the electromagnetic spectrum. We have investigated the optical properties of thin ITO films in the ultraviolet spectrum The transmission and reflection measurements showed that thin ITO films had better transparencies than thin Au films for wavelengths greater than 280 mn. Using a microwave compatible fabrication process, we have fabricated Au and ITO based Schottky photediodes on n-/n+ GaN epitaxial layers. We have made current-voltage (I-V), spectral quantum efficiency, and high-speed characterization of the fabricated devices. I-V characterization showed us that the Au-Schottky samples had better electrical characteristics mainly due to the larger Schottky barrier. However, due to the better optical transparency, ITO-Schottky devices exhibited higher quantum efficiencies compared to Au-Schottky devices. ITO-Schottky photodiodes with ∼80 nm thick ITO films resulted in a maximum quantum efficiency of 47%, whereas Au-Schottky photodiode samples with ∼10 nm thick Au films displayed a maximum efficiency of 27% in the visible-blind spectrum. UV/visible rejection ratios over three orders of magnitude were obtained for both samples. High-frequency characterization of the devices was performed via pulse-response measurements at 360 nm. ITO-Schottky photodiodes showed excellent high-speed characteristics with rise times as small as 12 psec and RC-time constant limited pulse-widths of 60 psec.
Open Access
ITO-schottky photodiodes for high-performance detection in the UV-IR spectrum
(IEEE, 2004) Bıyıklı, Necmi; Kimukin, I.; Butun, B.; Aytür, O.; Özbay, Ekmel
High-performance vertically illuminated Schottky photodiodes with indium-tin-oxide (ITO) Schottky layers were designed, fabricated, and tested. Ternary and quarternary III-V material systems (AlGaN-GaN, AlGaAs-GaAs, InAlGaAs-InP, and InGaAsP-InP) were utilized for detection in the ultraviolet (UV) (λ < 400 nm), near-IR (λ ∼ 850 nm), and IR (λ ∼ 1550 nm) spectrum. The material properties of thin ITO films were characterized. Using resonant-cavity-enhanced (RCE) detector structures, improved efficiency performance was achieved. Current-voltage, spectral responsivity, and high-speed measurements were carried out on the fabricated ITO-Schottky devices. The device performances obtained with different material systems are compared.
Open Access
Ultraviolet-visible nanophotonic devices
(2010) Bütün, Bayram
Recently in semiconductor market, III-Nitride materials and devices are of much interest due to their mechanical strength, radiation resistance, working in the spectrum from visible down to the deep ultraviolet region and solar-blind device applications. These properties made them strongest candidates for space telecommunication, white light generation, high power lasers and laser pumping light emitting diodes. Since, like other semiconductors, there have been material quality related issues, ongoing research efforts are concentrated on growing high quality crystals and making low p-type ohmic contact. Also, in light emitting device applications, similar to the visible and infrared spectrum components, there are challenging issues like high extraction efficiency and controlled radiation. In this thesis, we worked on growth and characterizations of high quality (In,Al)GaN based semiconductors, fabricating high performance photodiodes and light emitting diodes. We studied different surface modifications and possibilities of obtaining light emitting diode pumped organic/inorganic hybrid laser sources