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Selected Topics in Quantum Electronics, IEEE Journal of

Issue 6 • Date Nov.-Dec. 2014

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  • Front cover

    Article#: 0002101
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  • IEEE Journal of Selected Topics in Quantum Electronics publication information

    Article#: 0002201
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  • Table of Contents

    Article#: 0100604
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  • 2013–2014 List of Reviewers

    Article#: 9900203
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  • Introduction to Issue on Optical Detectors: Technologies and Applications

    Article#: 0200603
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  • Photonic High-Power 160-GHz Signal Generation by Using Ultrafast Photodiode and a High-Repetition-Rate Femtosecond Optical Pulse Train Generator

    Article#: 3803507
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (669 KB) |  | HTML iconHTML  

    We demonstrate photonic high-power MMW generation at subTHz (160 GHz) frequencies by using ultrafast near-ballistic unitraveling carrier photodiodes (NBUTC-PD), which have a miniaturized active area (24 μm2 ) and flip-chip bonding package for good heat-sinking. Under optical sinusoidal signal excitation with a ~85% modulation depth, 165-GHz optical-to-electrical 3-dB bandwidth, 18-mA saturation current, +5.11-dBm maximum output power at 160-GHz operating frequency has been demonstrated. In order to further mitigate device-heating, we developed a high-power pulsed optical signal source with increased optical modulation depth: a femtosecond optical short-pulse generator with extremely high repetition rate (160 GHz) and pulsewidth as short as 285 fs. With this novel source, we generated high MMW power (+7.8 dBm) with an effective 120% optical modulation depth at 160 GHz directly from the NBUTC-PD. View full abstract»

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  • Self-Aligned Microbonded Germanium Metal–Semiconductor–Metal Photodetectors Butt-Coupled to Si Waveguides

    Article#: 3800605
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    We present a butt-coupled Germanium (Ge) metal-semiconductor-metal photodetectors on silicon (Si) waveguides. This device is implemented by a novel process using self-aligned microbonding technique and rapid-melt-growth method for monolithically integrating single-crystal Ge and Si devices on the same plane. Through inserting a thin amorphous Si (a-Si) layer between the Ge and metal contact, the Schottky barrier height is modulated, which effectively reduces the dark current and increases the operation speed. The fabricated device shows a low dark current of 0.24 μA, a 3 dB bandwidth of 15 GHz and a responsivity of 0.25 A/W, at a bias voltage of -2.6 V for wavelength 1310 nm. View full abstract»

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  • Large-Area p-i-n Photodiode With High-Speed and High-Efficiency Across a Wide Optical Operation Window (0.85 to 1.55 μm)

    Article#: 3800807
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    We demonstrate novel InP based photodiodes, which eliminate the degradation in speed and efficiency under short wavelength (0.85 μm) operation and have a enlarged device diameter as compared to that of GaAs based PDs for the same desired speed performance. By inserting a p-type In0.52Al0.32Ga0.16As layer with an intermediary bandgap value (1.2 eV) between In0.52Al0.48As (1.47 eV) window and In0.53Ga0.47As (0.75 eV) absorption layers, the huge surface absorption (recombination), which would lead to efficiency degradation, under short wavelength excitation can be diluted. The slow hole transport in our structure can also be diminished due to the p-type doping in these absorption layers. Furthermore, the trade-offs between RC-limited bandwidth (device size) and carrier transient time in GaAs based PDs can be further released due to the excellent electron transport characteristic in the In0.53Ga0.47As (collector) layer. These devices with a large diameter as 62 μm, which is the usual size of 10 Gbit/s InP based PDs, can achieve wide 3-dB bandwidths; varying from 25 to 17 GHz when the operating wavelengths changes from 0.85 to 1.55 μm. A constant and high external efficiency (~74%) with a clear eye-opening at around 40 Gbit/s has also been achieved over this wide optical window. View full abstract»

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  • Optimized High Speed UTC Photodiode for 100 Gbit/s Applications

    Article#: 3801107
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    In this paper we present an optimized high-speed uni-traveling carrier photo-diode (UTC PD) for 100 Gbit/s applications. The designed photodiode operates at 1.55 μm wavelength with a 3 dB bandwidth exceeding 110 GHz, a dark current of 1 nA at -2 V and a peak saturation current of about 30 mA at -2 V. A 40% bandwidth improvement is achieved by employing new optimized transmission lines (TMLs) to equalize the intrinsic response of the detector. In addition, results of the tested UTC, using 100 Gbit/s NRZ modulation format show considerably improved eye quality. View full abstract»

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  • High-Speed InGaAs Photodetectors by Selective-Area MOCVD Toward Optoelectronic Integrated Circuits

    Article#: 3801807
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    We report selective-area growth of high-crystalline-quality InGaAs-based photodetectors with optimized InP/GaAs buffers on patterned (100)-oriented silicon-on-insulator (SOI) substrates by metal-organic chemical vapor deposition. The composite GaAs and InP buffer was grown using a two-temperature method. The island morphology of the low-temperature GaAs nucleation layer inside the growth well of the SOI substrate was optimized. A medium temperature GaAs layer was inserted prior to the typical high-temperature GaAs to further decrease the dislocation densities and antiphase boundaries. Both normal-incidence photodetectors and butt-coupled waveguide photodetectors were fabricated on the same substrate and showed a low dark current and high-speed performance. This result demonstrates a good potential of integrating photonic and electronic devices on the same Si substrate by direct epitaxial growth. View full abstract»

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  • Monolithic Germanium/Silicon Photodetectors With Decoupled Structures: Resonant APDs and UTC Photodiodes

    Article#: 3802214
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    The Ge/Si system is useful to realize avalanche photodetectors (APDs) operating at 1310~1550 nm because of the intrinsic advantages of complementary metal-oxide-semiconductor (CMOS) compatibility, high light-absorption of Ge, low ionization rate ratio of silicon, and high thermal conductivities of Si and Ge. With the Ge/Si system, it is convenient to realize photodetectors with decoupled structures including resonant Ge/Si APDs as well as uni-traveling carrier (UTC) photodiodes. The resonant Ge/Si APD with a separated absorption-charge-multiplication (SACM) structure, which decouples the light absorption and avalanche process, has high speed, high gain, and high gain-bandwidth product. The UTC photodiode, which decouples the light absorption and the carrier collection, is useful for high-power applications. This paper first reviews the structure and model of decoupled Ge/Si (A)PDs, particularly, the equivalent circuit models for explaining the peak enhancement of the frequency response in resonant SACM APDs. This model is also applied to UTC Ge/Si PDs developed recently for the high-power applications. View full abstract»

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  • High-Speed Photodiodes

    Article#: 3804507
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    To meet the challenge of broad bandwidth and high-responsivity numerous photodetector approaches have been investigated. Normal-incidence photodiodes have the advantages of relatively simple structures, high responsivity, and relaxed packaging constraints for bandwidths of a few gigahertz. Achieving acceptable responsivity at higher speed necessitates the use of waveguide structures. The emergence of Si photonics has also relied on developing suitable waveguide photodiodes. This paper reviews the technologies employed for high-speed photodiodes and state-of-the-art performance. View full abstract»

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  • Isolated Electron Injection Detectors With High Gain and Record Low Dark Current at Telecom Wavelength

    Article#: 3805106
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    We report on recent performance breakthroughs in a novel short-wave infrared linear-mode electron-injection-based detector. Detectors consist of InP material system with a type-II band alignment and provide high internal avalanche-free amplification mechanism. Measurements on devices with 10-μm injector diameter and 30-μm absorber diameter show internal dark current density of about 0.1 nA/cm2 at 160 K. Compared with our previous reported results, dark current is reduced by two orders of magnitude with no sign of surface leakage limitation down to the lowest measured temperature. Compared with the best-reported linear-mode avalanche photodetector, which is based on HgCdTe, the electron-injection detector shows over three orders of magnitude lower internal dark current density at all measured temperatures. Using a detailed simulation with experimentally measured parameters, dark count rate of 1 Hz at 90% photon detection efficiency at 210 K is anticipated. This is a significantly higher operating temperature compared with superconducting detectors with a similar performance. View full abstract»

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  • High Performance Room Temperature Rectenna IR Detectors Using Graphene Geometric Diodes

    Article#: 3801409
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    High performance rectenna detectors that operate at room temperature have been developed for the frequency range of terahertz to infrared (IR). We formed IR rectennas by coupling bowtie antennas to ultrafast diodes, called geometric diodes. Geometric diodes rely on geometric asymmetry and the long charge carrier mean-free path length of graphene to provide asymmetric current-voltage characteristics. The planar structure of the geometric diode provides the femtosecond RC time constant necessary for detection of IR frequencies. Fabricated IR rectennas using graphene geometric diodes have shown strong optical response to 28 THz CO2 laser illumination at room temperature. The detectivity (D*) and the noise equivalent power (NEP) of the IR rectennas are calculated to be on the order of 108 cm Hz1/2W-1 and 10-9 W Hz-1/2, respectively. Simulations show that with some improvement room temperature rectennas using graphene geometric diodes are able to achieve an NEP value as low as 10-11 W Hz-1/2. View full abstract»

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  • Unitraveling-Carrier Photodiodes for Terahertz Applications

    Article#: 3804210
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    Device design for unitraveling-carrier photodiodes (UTC-PDs) and their derivative structures is reconsidered from the point of view of terahertz (THz) applications. A key design procedure for maximizing their bandwidth is optimization by incorporating hybrid absorbers. The effect of quasi-field in p-type absorber is carefully examined. It has been shown that the initial velocity transient must be taken into account to evaluate the effective average velocity. Photomixers integrating a hybrid-absorber UTC-PD and a bow-tie antenna were fabricated and characterized. THz-wave generation by the photomixers in a frequency range of up to around 2.5 THz was confirmed. The observed THz-wave output exhibits significant changes with bias voltage, where the decrease in the output with increasing negative bias voltage is more pronounced at higher frequencies. This output behavior is due to the change in electron velocity in the diode depletion layer associated with the overshoot effect. From the dependence of the output power on frequency, effective electron velocity is found to be as high as $6 times 10^{7}$ cm/s at optimum bias voltage of -0.4 V. View full abstract»

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  • Noise Properties of Low-Temperature-Grown Co-Doped ZnO Nanorods as Ultraviolet Photodetectors

    Article#: 3800707
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    The growth of vertically aligned cobalt-doped ZnO (Co-ZnO) nanorods on a glass substrate using a low-temperature hydrothermal method is reported. A Co-ZnO nanorod metal-semiconductor-metal ultraviolet photodetector (PD) was also fabricated. The ratio of UV-to-visible rejection of the fabricated PD was approximately 11700 when biased at 1 V with a sharp cutoff at 380 nm. With an incident light wavelength of 380 nm and an applied bias of 1 V, the measured responsivity of the PD was found to be 19.8 A/W. Furthermore, the dark noise equivalent power (NEP) and photo NEP of the fabricated Co-ZnO nanorod MSM PD were 1.3 × 10-13 and 1.8 × 10-11 W at the corresponding dark detectivities (D*) and photo D* of 1.1 × 1014 and 7.3 × 1011 cm · Hz 0.5 · W -1, respectively. View full abstract»

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  • Photoconductive Gain and Noise Properties of ZnO Nanorods Schottky Barrier Photodiodes

    Article#: 3801204
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    In this investigation, ZnO nanorods Schottky barrier photodiodes were fabricated for UV detection. The Schottky barrier photodiodes had a rectifying current flow. Under 370 nm illumination, it was found that the ZnO nanorods Schottky barrier photodiodes showed high responsivity of 104.14 A/W at -1 V. The high responsivity can be attributed to large surface-to-volume ratio and oxygen adsorption and desorption at the ZnO surfaces. It was also found that the photocurrent linear increased with incident power density increased. The photocurrents have no obvious saturation at large bias, indicating the sample is very ideal for practice use. Further, under a -1 V applied bias, noise equivalent power and normalized detectivity (D*) were 8.01 × 10-13 Wand 2.77 × 1011 cm Hz0.5 W-1, respectively. View full abstract»

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  • Monolithic Multichannel Ultraviolet Photodiodes Based on (Mg,Zn)O Thin Films With Continuous Composition Spreads

    Article#: 3801606
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    We report on the fabrication of monolithic multichannel metal-semiconductor-metal photodiode arrays based on ternary (Mg,Zn)O thin films in wurtzite modification. The narrow bandwidth and the wavelength-selectivity of the device operating in visible-blind spectral range have been realized by employing a novel continuous composition spread approach relying on a single segmented target of pulsed-laser deposition. The Mg-content and subsequently the bandgap of thin films vary linearly along the compositional gradient across the wafer allowing the tuning of cutoff energies of the photodiode. In our device, the Mg-composition gradient of the active and optical filter layer (resulting in the narrow bandwidth of the photodiode) are designedly deposited with an angle of 72 ° with respect to each other. Here the onset of absorption is tuned over 430 meV and the bandwidth of the photodiodes is controlled from 270 meV down to 29 meV. View full abstract»

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  • See-Through $hbox{Ga}_{2}hbox{O}_{3}$ Solar-Blind Photodetectors for Use in Harsh Environments

    Article#: 3802006
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    This paper demonstrates the high-temperature operation of fully transparent solar-blind deep ultraviolet (DUV) metal-semiconductor-metal (MSM) photodetectors (PDs) employing β-Ga2O3 thin films with transmittance up to 80% from 400 to 900 nm without image blurring. Even at a bias up to 200 V, the β-Ga2O3 MSM PDs show dark current as low as ~1 nA. The dark current of β-Ga2O3 MSM PDs under significantly different oxygen concentration in the ambiences are similar, indicating that the high inertness to surface effect. Moreover, the responsivity and the working temperature of β-Ga2O3 MSM PDs at 10 V bias are 0.32 mA/W and as high as 700 K, respectively. Full recovery after 700-K operation demonstrates reliability and robustness of β-Ga2O3 PDs. The superior see-through features, electrical tolerance, inertness to surface effect, thermal stability, and solar-blind DUV photoresponse of β-Ga2O3 MSM PDs support the use in next-generation DUV PDs applications under harsh environments. View full abstract»

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  • Pd/ZnO Nanoparticles Based Schottky Ultraviolet Photodiodes Grown on Sn-Coated n-Si Substrates by Thermal Evaporation Method

    Article#: 3803106
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    This paper reports the ultraviolet (UV) detection characteristics of Pd/ZnO nanoparticles (NPs) based Schottky diodes grown on Sn coated n-Si substrates by thermal evaporation method. The measured current-voltage characteristics of the Pd/ZnO NPs/Sn/n-Si diodes under both the dark and UV illumination at wavelength of 365 nm have been presented for the applied bias voltage varying from -3 to 3 V. The as-fabricated photodiodes show a high-contrast ratio (i.e., the photocurrent to dark current ratio) of ~541.34, an excellent quantum efficiency of ~68%, a reasonably good responsivity of ~0.20 A/W at 365 nm, and -3 V reverse bias voltage at room temperature. View full abstract»

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  • Low-Frequency Noise Spectra of Laterally Bridged ZnO Microrod-Based Photodetectors

    Article#: 3802407
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    The laterally bridged ZnO microrods grown from an Au electrode applied to metal-semiconductor-metal photodetector was fabricated. Interlaced ZnO microrods with approximate single-crystalline structure can be grown from Au electrode fingers. The dark-current was 5.00 × 10-5 A with an applied voltage of 1 V. Highly dense lateral ZnO microrod-based photodetectors produce remarkable responsivity of 1.93 × 105 A/W. Moreover, an extremely high internal photoconductive gain of 6.28 × 105 exists in the fabricated photodetectors. For a given bandwidth of 10 kHz and 1 V applied bias, the noise equivalent power of photodetectors were estimated to be 1.86 × 10-13 W, and correspond to normalized detectivity of 1.12 × 1012 cm·Hz0.5 W-1. This result may be attributed to an internal photoconductive gain mechanism and high-density bridged ZnO microrods. Our approach provides a simple and seed-layer-free method to fabricate high-performance ultraviolet photodetectors. View full abstract»

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  • Amorphous InGaZnO Ultraviolet Phototransistors With a Thin Ga2O3 Layer

    Article#: 3803605
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    The authors report the fabrication of amorphous IGZO (a-IGZO) phototransistors with a thin Ga2O3 layer. It was found that the performances of the phototransistors depend strongly on the oxygen partial pressure during the deposition of the Ga2O3 layer. It was also found that the fabricated devices exhibited good electrical properties with electron mobility (μFE) of 13.2 cm2/V·s, subthreshold swing (SS) of 0.13 V/decade, and ON/OFF current ratio> 5 × 105. Furthermore, it was found that two cutoffs exist in the devices prepared with 25% oxygen partial pressure. The deep-ultraviolet (UV)-to-visible rejection ratio and near-UV-to-visible rejection ratio of the fabricated phototransistors were 104 and 20, respectively. View full abstract»

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  • Inverted Organic Photodetectors With ZnO Electron-Collecting Buffer Layers and Polymer Bulk Heterojunction Active Layers

    Article#: 3805207
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    We report inverted-type organic photodetectors with zinc oxide (ZnO) electron-collecting buffer layers and polymer:fullerene bulk heterojunction active layers. A visible light was detected by the inverted organic photodetectors when a background UV light was ON, whereas no photocurrent signal was measured for visible lights without the background UV light. Interestingly, UV lights solely were successfully detected without any surrounding UV light. The present devices exhibited fast and stable photo-responses under modulated or continuous UV-visible lights. View full abstract»

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  • Surface Plasmon-Enhanced GaN Metal–Insulator–Semiconductor Ultraviolet Detectors With Ag Nanoislands Embedded in a Silicon Dioxide Gate Layer

    Article#: 3801005
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    GaN metal-insulator-semiconductor ultraviolet (UV) photodetectors (PDs) with silver (Ag) nanoislands on a silicon dioxide (SiO2) gate layer were fabricated and characterized. Samples with different Ag mass thickness values were prepared on SiO2/sapphire template substrates and characterized by transmission spectral to confirm the surface plasmon resonance (SPR) effect. By examining the transmission spectra of Ag nanoislands on the SiO2/sapphire substrates, two transmission dips were observed in each spectrum. The transmission dip in the blue region was more significant than that in the UV region, but visible light with photon energy less than the bandgap of GaN was not absorbed to generate significant response. By introducing the Ag nanoislands, the UV-to-visible rejection ratio (RUV/vis) of spectral responsivity was at least ten times higher than those of PDs without Ag nanoislands. The RUV/vis enhancement was mainly due to the increase in UV response caused by SPR at approximately 360 nm induced by Ag nanoislands to enhance UV-light absorption. View full abstract»

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  • Al$_{bf 0.52}$In$_{bf 0.48}$P SAM-APD as a Blue-Green Detector

    Article#: 3801305
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    We demonstrate an Al0.52In0.48 P homo-junction Separate Absorption Multiplication Avalanche Photodiode as a detector with narrow spectral response in the blue-green part of the optical spectrum. Due to its wide band-gap, this device has a dark current density of <; 8 nA cm-2 at 99.9% of the breakdown voltage at room temperature. This device has a peak responsivity at 483 nm of 0.15 A/W when punched-through and is capable of an avalanche gain higher than 100. View full abstract»

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Aims & Scope

Papers published in the IEEE Journal of Selected Topics in Quantum Electronics fall within the broad field of science and technology of quantum electronics of a device, subsystem, or system-oriented nature.

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Meet Our Editors

Editor-in-Chief
John Cartledge
Queen's University