Browsing by Subject "Photodetectors"

Now showing 1 - 20 of 69

Open Access
1.3 μm GaAs based resonant cavity enhanced Schottky barrier internal photoemission photodetector
(IEEE, Piscataway, NJ, United States, 2000) Necmi, B.; Kimukin, I.; Özbay, Ekmel; Tuttle, G.
GaAs based photodetectors operating at 1.3 μm that depend on internal photoemission as the absorption mechanism were fabricated. Quantum efficiency (QE) was increased using resonant cavity enhancement (RCE) effect.
Open Access
100-GHz resonant cavity enhanced Schottky photodiodes
(Institute of Electrical and Electronics Engineers, 1998) Onat, B. M.; Gökkavas, M.; Özbay, Ekmel; Ata, E. P.; Towe, E.; Ünlü, M. S.
Resonant cavity enhanced (RCE) photodiodes are promising candidates for applications in optical communications and interconnects where ultrafast high-efficiency detection is desirable. We have designed and fabricated RCE Schottky photodiodes in the (Al, In) GaAs material system for 900-nm wavelength. The observed temporal response with 10-ps pulsewidth was limited by the measurement setup and a conservative estimation of the bandwidth corresponds to more than 100 GHz. A direct comparison of RCE versus conventional detector performance was performed by high speed measurements under optical excitation at resonant wavelength (895 nm) and at 840 nm where the device functions as a single-pass conventional photodiode. A more than two-fold bandwidth enhancement with the RCE detection scheme was demonstrated.
Open Access
45 GHz bandwidth-efficiency resonant cavity enhanced ITO-Schottky photodiodes
(OSA, 2001) Bıyıklı, Necmi; Kimukin, İbrahim; Aytür, Orhan; Özbay, Ekmel; Gökkavas, M.; Ünlü, M. S.
We demonstrated high-performance resonant cavity enhanced ITO-Schottky photodiodes. We achieved a peak efficiency of 75% around 820 nm with a 3-dB bandwidth of 60 GHz resulting in a bandwidth-efficiency product of 45 GHz.
Open Access
45-GHz bandwidth-efficiency resonant-cavity-enhanced ITO-Schottky photodiodes
(IEEE, 2001) Bıyıklı, Necmi; Kimukin, I.; Aytür, O.; Gökkavas, M.; Ünlü, M. S.; Özbay, Ekmel
High-speed Schottky photodiodes suffer from low efficiency mainly due to the thin absorption layers and the semitransparent Schottky-contact metals. We have designed, fabricated and characterized high-speed and high-efficiency AlGaAs-GaAs-based Schottky photodiodes using transparent indium-tin-oxide Schottky contact material and resonant cavity enhanced detector structure. The measured devices displayed resonance peaks around 820 nm with 75% maximum peak efficiency and an experimental setup limited temporal response of 11 ps pulsewidth. The resulting 45-GHz bandwidth-efficiency product obtained from these devices corresponds to the best performance reported to date for vertically illuminated Schottky photodiodes.
Open Access
AlGaN quadruple-band photodetectors
(IEEE, 2009) Gökkavas, Mutlu; Bütün, Serkan; Caban, P.; Strupinski, W.; Özbay, Ekmel
Quadruple back-illuminated ultraviolet metal-semiconductor-metal photodetectors with four different spectral responsivity bands were demonstrated. The average of the full-width at half-maximum (FWHM) of the quantum efficiency peaks was 9.98 nm.
Open Access
AlxGa1-xN-based avalanche photodiodes with high reproducible avalanche gain
(2008) Tut, Turgut; Gökkavas, Mutlu; Özbay, Ekmel
We report high performance solar-blind photodetectors with reproducible avalanche gain as high as 1570 under ultraviolet illumination. The solar-blind photodetectors have a sharp cut-off around 276 nm. The dark currents of the 40 μm diameter devices are measured to be lower than 8 femto-amperes for bias voltages up to 20 V. The responsivity of the photodetectors is 0.13 A/W at 272 nm under 20 V reverse bias. The thermally limited detectivity is calculated as D* = 1.4 × 1014 cm Hz1/2 W-1 for a 40 μm diameter device. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
Open Access
Atomic layer deposited Al 2O 3 passivation of type II InAs/GaSb superlattice photodetectors
(AIP, 2012) Salihoğlu, Ömer; Muti, Abdullah; Kutluer, Kutlu; Tansel, T.; Turan, R.; Kocabaş, Coşkun; Aydınlı, Atilla
Taking advantage of the favorable Gibbs free energies, atomic layer deposited (ALD) aluminum oxide (Al 2O 3) was used as a novel approach for passivation of type II InAs/GaSb superlattice (SL) midwave infrared (MWIR) single pixel photodetectors in a self cleaning process (λ cut-off ∼ 5.1 m). Al 2O 3 passivated and unpassivated diodes were compared for their electrical and optical performances. For passivated diodes, the dark current density was improved by an order of magnitude at 77 K. The zero bias responsivity and detectivity was 1.33 A/W and 1.9 × 10 13 Jones, respectively at 4μm and 77 K. Quantum efficiency (QE) was determined as 41 for these detectors. This conformal passivation technique is promising for focal plane array (FPA) applications. © 2012 American Institute of Physics.
Open Access
Au/TiO2 nanorod-based Schottky-type UV photodetectors
(Wiley, 2012-10-12) Karaagac, H.; Aygun, L. E.; Parlak, M.; Ghaffari, M.; Bıyıklı, Necmi; Okyay, Ali Kemal
TiO2 nanorods (NRs) were synthesized on fluorine-doped tin oxide (FTO) pre-coated glass substrates using hydrothermal growth technique. Scanning electron microscopy studies have revealed the formation of vertically-aligned TiO2 NRs with length of similar to 2 mu m and diameter of 110128 nm, homogenously distributed over the substrate surface. 130 nm thick Au contacts using thermal evaporation were deposited on the n-type TiO2 NRs at room temperature for the fabrication of NR-based Schottky-type UV photodetectors. The fabricated Schottky devices functioned as highly sensitive UV photodetectors with a peak responsivity of 134.8 A/W (lambda = 350 nm) measured under 3 V reverse bias. (c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Open Access
CdSe/ZnS core-shell nanocrystal based scintillators for enhanced detection in UV
(IEEE, 2006) Demir, Hilmi Volkan; Soğancı, İbrahim Murat; Mutlugün, Evren
In this work, we present a novel scintillator that incorporates CdSe/ZnS core-shell nanocrystals to utilize both their high quantum fluorescence efficiency in the visible and high optical absorption in the UV for the purpose of facilitating UV imaging on a Si platform. Here we demonstrate enhancement in UV detection up to 800% with respect to the host polymer in the UV.
Open Access
Dark current reduction in ultraviolet metal-semiconductor-metal photodetectors based on wide band-gap semiconductors
(IEEE, 2009-10) Bütün, Serkan; Gökkavas, Mutlu; Yu, HongBo; Strupinski, Vlodek; Özbay, Ekmel
Photodetectors on semi-insulating GaN templates were demonstrated. They exhibit lower dark current compared to photodetectors fabricated on regular GaN templates. Similar behavior observed in photodetectors fabricated on epitaxially thick SiC templates. © 2009 IEEE.
Open Access
Deep-ultraviolet Al0.75Ga0.25N photodiodes with low cutoff wavelength
(AIP Publishing LLC, 2006-03-21) Bütün, S.; Tut, T.; Bütün, B.; Gökkavas, M.; Yu, H.; Özbay, Ekmel
Deep ultraviolet Al0.75Ga0.25N metal-semiconductor-metal photodetectors with high Al concentration have been demonstrated. A metal-organic chemical vapor deposition grown high quality Al0.75Ga0.25N layer was used as a template. Spectral responsivity, current-voltage, optical transmission, and noise measurements were carried out. The photodetectors exhibited a 229 nm cutoff wavelength and a peak responsivity of 0.53 A/W at 222 nm. Some 100x100 mu m(2) devices have shown a dark current density of 5.79x10(-10) A/cm(2) under 50 V bias. An ultraviolet-visible rejection ratio of seven orders of magnitude was obtained from the fabricated devices.
Open Access
Design and optimization of high-speed resonant cavity enhanced Schottky photodiodes
(Institute of Electrical and Electronics Engineers, 1999-02) Gökkavas, M.; Onat, B. M.; Özbay, Ekmel; Ata, E. P.; Xu, J.; Towe, E.; Ünlü, M. S.
Resonant cavity enhanced (RCE) photodiodes (PD's) are promising candidates for applications in optical communications and interconnects where high-speed high-efficiency photodetection is desirable. In RCE structures, the electrical properties of the photodetector remain mostly unchanged; however, the presence of the microcavity causes wavelength selectivity accompanied by a drastic increase of the optical field at the resonant wavelengths. The enhanced optical field allows to maintain a high efficiency for faster transit-time limited PD's with thinner absorption regions. The combination of an RCE detection scheme with Schottky PD's allows for the fabrication of high-performance photodetectors with relatively simple material structures and fabrication processes. In top-illuminated RCE Schottky PD's, a semitransparent Schottky contact can also serve as the top reflector of the resonant cavity. We present theoretical and experimental results on spectral and high-speed properties of GaAs-AlAs-InGaAs RCE Schottky PD's designed for 900-nm wavelength.
Open Access
Design, fabrication and characterization of high-performance solarblind AlGaN photodetectors
(SPIE, 2005) Özbay, Ekmel
Design, fabrication, and characterization of high-performance AlxGal-xN-based photodetectors for solar-blind applications are reported. AlxGal-xN heterostructures were designed for Schottky, p-i-n, and metal-semiconductor-metal (MSM) photodiodes. The resulting solar-blind AlGaN detectors exhibited low dark current, high detectivity, and high bandwidth.
Open Access
Dual-color ultraviolet metal-semiconductor-metal AlGaN photodetectors
(AIP Publishing LLC, 2006) Gökkavas, M.; Bütün, S.; Yu, H.; Tut, T.; Bütün, B.; Özbay, Ekmel
Backilluminated ultraviolet metal-semiconductor-metal photodetectors with different spectral responsivity bands were demonstrated on a single Alx Ga1-x N heterostructure. This was accomplished by the incorporation of an epitaxial filter layer and the recess etching of the surface. The 11 nm full width at half maximum (FWHM) responsivity peak of the detector that was fabricated on the as-grown surface was 0.12 AW at 310 nm with 10 V bias, whereas the 22 nm FWHM responsivity peak of the detector fabricated on the recess-etched surface was 0.1 AW at 254 nm with 25 V bias. Both detectors exhibited excellent dark current characteristics with less than 10 fA leakage current. © 2006 American Institute of Physics.
Open Access
Electrical performance of InAs/AlSb/GaSb superlattice photodetectors
(Academic Press, 2016) Tansel, T.; Hostut M.; Elagoz, S.; Kilic A.; Ergun, Y.; Aydınlı, Atilla
Temperature dependence of dark current measurements is an efficient way to verify the quality of an infrared detector. Low dark current density values are needed for high performance detector applications. Identification of dominant current mechanisms in each operating temperature can be used to extract minority carrier lifetimes which are highly important for understanding carrier transport and improving the detector performance. InAs/AlSb/GaSb based T2SL N-structures with AlSb unipolar barriers are designed for low dark current with high resistance and detectivity. Here we present electrical and optical performance of such N-structure photodetectors.
Open Access
Electronic and optical properties of 4.2 μm"N" structured superlattice MWIR photodetectors
(Elsevier, 2013) Salihoglu, O.; Hostut M.; Tansel, T.; Kutluer, K.; Kilic A.; Alyoruk, M.; Sevik, C.; Turan, R.; Ergun, Y.; Aydınlı, Atilla
We report on the development of a new structure for type II superlattice photodiodes that we call the "N" design. In this new design, we insert an electron barrier between InAs and GaSb in the growth direction. The barrier pushes the electron and hole wavefunctions towards the layer edges and under bias, increases the overlap integral by about 25% leading to higher detectivity. InAs/AlSb/GaSb superlattices were studied with density functional theory. Both AlAs and InSb interfaces were taken into account by calculating the heavy hole-light hole (HH-LH) splittings. Experiments were carried out on single pixel photodiodes by measuring electrical and optical performance. With cut-off wavelength of 4.2 μm at 120 K, temperature dependent dark current and detectivity measurements show that the dark current is 2.5 × 10 -9 A under zero bias with corresponding R0A resistance of 1.5 × 104 Ω cm2 for the 500 × 500 μm2 single pixel square photodetectors. Photodetector reaches BLIP condition at 125 K with the BLIP detectivity (DBLIP) of 2.6 × 10 10 Jones under 300 K background and -0.3 V bias voltage. © 2012 Elsevier B.V. All rights reserved.
Open Access
Fabrication of high-speed resonant cavity enhanced schottky photodiodes
(Institute of Electrical and Electronics Engineers, 1997-05) Özbay, Ekmel; Islam, M. S.; Onat, B.; Gökkavas, M.; Aytür, O.; Tuttle, G.; Towe, E.; Henderson, R. H.; Ünlü, M. S.
We report the fabrication and testing of a GaAs-based high-speed resonant cavity enhanced (RCE) Schottky photodiode. The top-illuminated RCE detector is constructed by integrating a Schottky contact, a thin absorption region (In0.8Ga0.92As) and a distributed AlAs-GaAs Bragg mirror. The Schottky contact metal serves as a high-reflectivity top mirror in the RCE detector structure. The devices were fabricated by using a microwave-compatible fabrication process. The resulting spectral photo response had a resonance around 895 nm, in good agreement with our simulations. The full-width-at-half-maximum (FWHM) was 15 nm, and the enhancement factor was in excess of 6. The photodiode had an experimental setup limited temporal response of 18 ps FWHM, corresponding to a 3-dB bandwidth of 20 GHz.
Open Access
GaN/AlGaN-based UV photodetectors with performances exceeding the PMTS
(2008) Tut, Turgut
The recent developments in high Al-content AlxGa1−xN material growth technology made it possible to fabricate high performance solar-blind photodetectors operating in the ultraviolet (UV) spectral region with improved receiver sensitivity, low noise, low dark current density, and high speed. AlGaN-based Schottky, p-i-n, and metal-semiconductor-metal photodetectors (MSM) with very high performances have already been demonstrated. The UVfiltering nature of the atmospheric ozone molecules blocks the solar radiation to reach the earth’s surface for wavelengths shorter than 280 nm. In this case, UV photodetectors with cutoff wavelengths around 280 nm, which are also called solarblind detectors, can detect very weak UV signals under intense background radiation. These devices have important applications including missile plume detection, chemical/biological agent sensing, flame alarms, covert space-tospace and submarine communications, ozone-layer monitoring, and gas detection. Due to their high responsivity (600 A/W), high speed, high cathode gain (on the order of a million), and low dark current properties, photomultiplier tubes (PMTs) are frequently used in such applications. However, PMTs are very expensive and bulky. Besides, they require a cooling system, and they have high operation voltages in excess of 1000 V. To achieve solar-blind detection, PMTs should also be integrated with complex and expensive filters. In order to avoid these disadvantages, high performance solid-state UV photodetectors with high internal gain are needed. Wide band-gap semiconductor photodetectors, such as AlxGa1−xN with x=0.4, are ideal candidates for this purpose. These devices are intrinsically solar blind, in which no additional filters are needed, they have low noise, and fast response times. The lack of high internal gain has been the major limitation for the usage of AlGaN photodetectors for applications that require high sensitivity detectors. There have been several theoretical research works that examined the avalanche effect in GaN and AlGaN-based structures. However, reproducible high gain in AlGaN-based APDs is still a major limitation. We have designed, fabricated, GaN/AlGaN based photodetectors, and according to characterization measurements, the Schottky, p-i-n, and avalanche detectors have high performance in terms of quantum efficiency, dark current, detectivity, high speed response, and high reproducible avalanche gain.
Open Access
High efficiency monolithic photodetectors for integrated optoelectronics in the near infrared
(IEEE, 2009) Okyay, Ali Kemal; Onbaşlı, M. Cengiz; Ercan, Burcu; Yu H.-Y.; Ren, S.; Miller, D.A.B.; Saraswat, K.C.; Nayfeh, A.M.
Monolithic Germanium photodetectors integrated on Si with external efficiency up to 68% at 1550nm and low dark current density 3.2mA/cm2 are demonstrated. The absorption edge red shifted by 47nm corresponding to bandgap energy reduced by 24meV. © 2009 IEEE.
Open Access
High performance infrared photodetectors up to 2.8 μm wavelength based on lead selenide colloidal quantum dots
(OSA - The Optical Society, 2017) Thambidurai, M.; Jang, Y.; Shapiro, A.; Yuan, G.; Xiaonan, H.; Xuechao, Y.; Wang, Q. J.; Lifshitz, E.; Demir, Hilmi Volkan; Dang C.
The strong quantum confinement effect in lead selenide (PbSe) colloidal quantum dots (CQDs) allows to tune the bandgap of the material, covering a large spectral range from mid- to near infrared (NIR). Together with the advantages of low-cost solution processability, flexibility and easy scale-up production in comparison to conventional semiconductors especially in the mid- to near infrared range, PbSe CQDs have been a promising material for infrared optoelectronic applications. In this study, we synthesized monodisperse and high purity PbSe CQDs and then demonstrated the photodetectors working at different wavelengths up to 2.8 μm. Our high quality PbSe CQDs show clear multiple excitonic absorption peaks. PbSe CQD films of different thicknesses were deposited on interdigitated platinum electrodes by a simple drop casting technique to make the infrared photodetectors. At room temperature, the high performances of our PbSe CQD photodetectors were achieved with maximum responsivity, detectivity and external quantum efficiency of 0.96 A/W, 8.13 × 109 Jones and 78% at 5V bias. Furthermore, a series of infrared LEDs with a broad wavelength range from 1.5 μm to 3.4 μm was utilized to demonstrate the performance of our fabricated photodetectors with various PbSe CQD film thicknesses.