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4.  High Power Mid-Infrared Quantum Cascade Lasers Grown on GaAs
Steven Slivken and Manijeh Razeghi
Photonics 2022, 9(4), 231 (COVER ARTICLE) ...[Visit Journal]
The motivation behind this work is to show that InP-based intersubband lasers with high power can be realized on substrates with significant lattice mismatch. This is a primary concern for the integration of mid-infrared active optoelectronic devices on low-cost photonic platforms, such as Si. As evidence, an InP-based mid-infrared quantum cascade laser structure was grown on a GaAs substrate, which has a large (4%) lattice mismatch with respect to InP. Prior to laser core growth, a metamorphic buffer layer of InP was grown directly on a GaAs substrate to adjust the lattice constant. Wafer characterization data are given to establish general material characteristics. A simple fabrication procedure leads to lasers with high peak power (>14 W) at room temperature. These results are extremely promising for direct quantum cascade laser growth on Si substrates. [reprint (PDF)]
 
3.  High Power Mid-Infrared Quantum Cascade Lasers Grown on Si
Steven Slivken, Nirajman Shrestha, and Manijeh Razeghi
Photonics, vol. 9, 626 ...[Visit Journal]
This article details the demonstration of a strain-balanced, InP-based mid-infrared quantum cascade laser structure that is grown directly on a Si substrate. This is facilitated by the creation of a metamorphic buffer layer that is used to convert from the lattice constant of Si (0.543 nm) to that of InP (0.587 nm). The laser geometry utilizes two top contacts in order to be compatible with future large-scale integration. Unlike previous reports, this device is capable of room temperature operation with up to 1.6 W of peak power. The emission wavelength at 293 K is 4.82 um, and the device operates in the fundamental transverse mode. [reprint (PDF)]
 
3.  Continuous wave quantum cascade lasers with 5.6 W output power at room temperature and 41% wall-plug efficiency in cryogenic operation
F. Wang, S. Slivken, D. H. Wu, Q. Y. Lu, and M. Razeghi
AIP Advances 10, 055120-- May 19, 2020 ...[Visit Journal]
In this paper, we report a post-polishing technique to achieve nearly complete surface planarization for the buried ridge regrowth processing of quantum cascade lasers. The planarized device geometry improves the thermal conduction and reliability and, most importantly, enhances the power and efficiency in continuous wave operation. With this technique, we demonstrate a high continuous wave wall-plug efficiency of an InP-based quantum cascade laser reaching ∼41% with an output power of ∼12 W from a single facet operating at liquid nitrogen temperature. At room temperature, the continuous wave output power exceeds the previous record, reaching ∼5.6 W. [reprint (PDF)]
 
3.  High-brightness LWIR quantum cascade lasers
F. Wang, S. Slivken, and M. Razeghi
Optics Letters, vol. 46, No. 20, 5193 ...[Visit Journal]
Long-wave infrared (LWIR, lambda~8-12 um) quantum cascade lasers (QCLs) are drawing increasing interest, as they provide the possibility of long-distance transmission of light through the atmosphere owing to the reduced water absorption. However, their development has been lagging behind the shorter wavelength QCLs due to much bigger technological challenges. In this Letter, through band structure engineering based on a highly localized diagonal laser transition strategy and out-coupler design using an electrically isolated taper structure, we demonstrate high beam quality single-mode LWIR QCLs with high-brightness (2.0 MW cm-2 sr-1 for lambda~10 um, 2.2 MW cm-2 sr-1 for lambda~9 um, 5.0 MW cm-2 sr-1 for lambda~8 um) light extraction from a single facet in continuous-wave operation at 15 oC. These results mark an important milestone in exploring the lighting capability of inter-sub-band semiconductor lasers in the LWIR spectral range. [reprint (PDF)]
 
3.  Solar-blind photodetectors based on Ga2O3 and III-nitrides
Ryan McClintock; Alexandre Jaud; Lakshay Gautam; Manijeh Razeghi
Proc. SPIE 11288, Quantum Sensing and Nano Electronics and Photonics XVII, 1128803-- January 31, 2020 ...[Visit Journal]
Recently, there has been a surge of interest in the wide bandgap semiconductors for solar blind photo detectors (SBPD). This work presents our recent progress in the growth/doping of AlGaN and Ga2O3 thin films for solar blind detection applications. Both of these thin films grown are grown by metal organic chemical vapor deposition (MOCVD) in the same Aixtron MOCVD system. Solar-blind metal-semiconductor-metal photodetectors were fabricated with Ga2O3. Spectral responsivity studies of the MSM photodetectors revealed a peak at 261 nm and a maximum EQE of 41.7% for a −2.5 V bias. We have also demonstrated AlGaN based solar-blind avalanche photodiodes with a gain in excess of 57,000 at ~100 volts of reverse bias. This gain can be attributed to avalanche multiplication of the photogenerated carriers within the device. Both of these devices show the potential of wide bandgap semiconductors for solar blind photo detectors. [reprint (PDF)]
 
3.  Geiger-Mode Operation of AlGaN Avalanche Photodiodes at 255 nm
Lakshay Gautam, Alexandre Guillaume Jaud, Junhee Lee, Gail J. Brown, Manijeh Razeghi
Published in: IEEE Journal of Quantum Electronics ( Volume: 57, Issue: 2, April 2021) ...[Visit Journal]
We report the Geiger mode operation of back-illuminated AlGaN avalanche photodiodes. The devices were fabricated on transparent AlN templates specifically for back-illumination to leverage hole-initiated multiplication. The spectral response was analyzed with a peak detection wavelength of 255 nm with an external quantum efficiency of ~14% at zero bias. Low-photon detection capabilities were demonstrated in devices with areas 25 μm×25 μm. Single photon detection efficiencies of ~5% were achieved. [reprint (PDF)]
 
3.  Comparison of PLD-Grown p-NiO/n-Ga2O3 Heterojunctions on Bulk Single Crystal β-Ga2O3 and r-plane Sapphire Substrates
D. J. Rogers , V. E. Sandana, F. Hosseini Teherani and M. Razeghi
Proc. of SPIE Vol. 12895, Quantum Sensing and Nano Electronics and Photonics XX, 128870J (28 January - 1 February 2024 San Francisco)doi: 10.1117/12.3012511 ...[Visit Journal]
p-NiO/n-Ga2O3 heterostructures were formed on single crystal (-201) β (monoclinic) Ga2O3 and r-sapphire substrates by Pulsed Laser Deposition. Ring mesa layer stacks were created using a shadow mask during growth. X-Ray diffraction studies were consistent with the formation of (111) oriented fcc NiO on the bulk Ga2O3 and randomly oriented fcc NiO on (102) oriented β-Ga2O3 /r-sapphire. RT optical transmission studies revealed bandgap energy values of ~3.65 eV and ~5.28 eV for the NiO and Ga2O3 on r-sapphire. p-n junction devices were formed by depositing gold contacts on the layer stacks using shadow masks in a thermal evaporator. Both heterojunctions showed rectifying I/V characteristics. On bulk Ga2O, the junction showed a current density over 16mA/cm2 at +20V forward bias and a reverse bias leakage current over 3 orders of magnitude lower at -20V (1 pA). On Ga2O3/r-sapphire the forward bias current density at +15V was about an order of magnitude lower than for the p-NiO/bulk n-Ga2O3 heterojunction while the reverse bias leakage current at -15V (~ 20 pA) was an order of magnitude higher. Hence the NiO/bulk Ga2O3 junction was more rectifying. Upon illumination with a Xenon lamp a distinct increase in current was observed for the IV curves in both devices (four orders of magnitude for -15V reverse bias in the case of the p-NiO/bulk n-Ga2O3 heterojunction). The p-NiO/n-Ga2O3/rsapphire junction gave a spectral responsivity with a FWHM value of 80nm and two distinct response peaks (with maxima at 230 and 270nm) which were attributed to carriers being photogenerated in the Ga2O3 underlayer. For both devices time response studies showed a 10%/90% rise and fall of the photo generated current upon shutter open and closing which was relatively abrupt (millisecond range), and there was no evidence of significant persistent photoconductivity. [reprint (PDF)]
 
3.  Performance analysis of infrared heterojunction phototransistors based on Type-II superlattices
Jiakai Li, Arash Dehzangi, Manijeh Razeghi
Infrared Physics & Technology Volume 113, March 2021, 103641 ...[Visit Journal]
In this study, a comprehensive analysis of the n-p-n infrared heterojunction phototransistors (HPTs)based on Type-II superlattices has been demonstrated. Different kinds of Type-II superlattices were carefully chosen for the emitter, base, and collector to improve the optical performance. The effects of different device parameters include emitter doping concentration, base doping concentration, base thickness and energy bandgap difference between emitter and base on the optical gain of the HPTs have been investigated. By scaling the base thickness to 20 nm, the HPT exhibits an optical gain of 345.3 at 1.6 μm at room temperature. For a 10 μm diameter HPT device, a −3 dB cut-off frequency of 5.1 GHz was achieved under 20 V at 150 K. [reprint (PDF)]
 
3.  Multi-band SWIR-MWIR-LWIR Type-II superlattice based infrared photodetector
Manijeh Razeghi, Arash Dehzangi, Jiakai Li
Results in Optics Volume 2, January 2021, 100054 https://doi.org/10.1016/j.rio.2021.100054 ...[Visit Journal]
Type-II InAs/GaSb superlattices (T2SLs) has drawn a lot of attention since it was introduced in 1970, especially for infrared detection as a system of multi-interacting quantum wells. In recent years, T2SL material system has experienced incredible improvements in material quality, device structure designs and device fabrication process, which elevated the performances of T2SL-based photo-detectors to a comparable level to the state-of-the-art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). As a pioneer in the field, center for quantum devices (CQD) has been involved in growth, design, characterization, and introduction of T2SL material system for infrared photodetection. In this review paper, we will present the latest development of bias-selectable multi-band infrared photodetectors at the CQD, based on InAs/GaSb/AlSb and InAs/InAs1-xSbx type-II superlattice. [reprint (PDF)]
 
3.  High operating temperature midwave infrared photodiodes and focal plane arrays based on type-II InAs/GaSb superlattices
S. Abdollahi Pour, E.K. Huang, G. Chen, A. Haddadi, B.M. Nguyen and M. Razeghi
Applied Physics Letters, Vol. 98, No. 14, p. 143501-1-- April 4, 2011 ...[Visit Journal]
The dominant dark current mechanisms are identified and suppressed to improve the performance of midwave infrared InAs/GaSb Type-II superlattice photodiodes at high temperatures. The optimized heterojunction photodiode exhibits a quantum efficiency of 50% for 2 μm thick active region without any bias dependence. At 150 K, R0A of 5100 Ω·cm² and specific detectivity of 1.05×1012 cm·Hz0.5·W-1 are demonstrated for a 50% cutoff wavelength of 4.2 μm. Assuming 300 K background temperature and 2π field of view, the performance of the detector is background limited up to 180 K, which is improved by 25 °C compared to the homojunction photodiode. Infrared imaging using f/2.3 optics and an integration time of 10.02 ms demonstrates a noise equivalent temperature difference of 11 mK at operating temperatures below 120 K. [reprint (PDF)]
 
3.  Demonstration of Planar Type-II Superlattice-Based Photodetectors Using Silicon Ion-Implantation
Arash Dehzangi, Donghai Wu, Ryan McClintock, Jiakai Li, Alexander Jaud and Manijeh Razeghi
Photonics 2020, 7(3), 68; https://doi.org/10.3390/photonics7030068-- September 3, 2020 ...[Visit Journal]
In this letter, we report the demonstration of a pBn planar mid-wavelength infrared photodetectors based on type-II InAs/InAs1−xSbx superlattices, using silicon ion-implantation to isolate the devices. At 77 K the photodetectors exhibited peak responsivity of 0.76 A/W at 3.8 µm, corresponding to a quantum efficiency, without anti-reflection coating, of 21.5% under an applied bias of +40 mV with a 100% cut-off wavelength of 4.6 µm. With a dark current density of 5.21 × 10−6 A/cm2, under +40 mV applied bias and at 77 K, the photodetector exhibited a specific detectivity of 4.95 × 1011 cm·Hz1/2/W. [reprint (PDF)]
 
3.  Demonstration of type-II superlattice MWIR minority carrier unipolar imager for high operation temperature application
Guanxi Chen, Abbas Haddadi, Anh-Minh Hoang, Romain Chevallier, and Manijeh Razeghi
Optics Letters Vol. 40, Iss. 1, pp. 29–32-- December 18, 2014 ...[Visit Journal]
An InAs/GaSb type-II superlattice-based mid-wavelength infrared (MWIR) 320×256 unipolar focal plane array (FPA) using pMp architecture exhibited excellent infrared image from 81 to 150 K and ∼98% operability, which illustrated the possibility for high operation temperature application. At 150 K and −50  mV operation bias, the 27 μm pixels exhibited dark current density to be 1.2×10−5  A/cm², with 50% cutoff wavelength of 4.9 μm, quantum efficiency of 67% at peak responsivity (4.6 μm), and specific detectivity of 1.2×1012 Jones. At 90 K and below, the 27 μm pixels exhibited system limited dark current density, which is below 1×10−9  A/cm², and specific detectivity of 1.5×1014 Jones. From 81 to 100 K, the FPA showed ∼11  mK NEDT by using F/2.3 optics and a 9.69 ms integration time. [reprint (PDF)]
 
3.  Fabrication of 12 µm pixel-pitch 1280 × 1024 extended short wavelength infrared focal plane array using heterojunction type-II superlattice-based photodetector
Arash Dehzangi , Abbas Haddadi, Romain Chevallier, Yiyun Zhang and Manijeh Razegh
Semicond. Sci. Technol. 34, 03LT01-- February 4, 2019 ...[Visit Journal]
We present an initial demonstration of a 1280 × 1024 extended short-wavelength infrared focal plane array (FPA) imager with 12μm pixel-pitch based on type–II InAs/AlSb/GaSb superlattice heterojunction photodetectors, with a novel bandstructure-engineered photo-generated carrier extractor as the window layer in the hetero structure to efficiently extract the photo-generated carriers. This heterostructure with a larger bandgap top window/contact layer leads to the device having lower dark current density compared to conventional pn junction devices. The large format FPA was fabricated with 12 μm pixel-pitch using a developed fabrication process. Test pixels fabricated separately exhibit 100% cut–off wavelengths of ∼2.22, ∼2.34μm, and ∼2.45μm at 150, 200K, and 300K. The test devices achieve saturated quantum efficiency values under zero bias of 54.3% and 68.4% at 150 and 300K, under back-side illumination and without any anti-reflection coating. At 150K, these photodetectors exhibit dark current density of 1.63 × 10−7 A·cm−2 under −20mV applied bias providing a specific detectivity of 1.01 × 1011 cm ·Hz½/W at 1.9μm. [reprint (PDF)]
 
3.  High operability 1024 x 1024 long wavelength Type-II superlattice focal plane array
A. Haddadi, S.R. Darvish, G. Chen, A.M. Hoang, B.M. Nguyen and M. Razeghi
IEEE Journal of Quantum Electronics (JQE), Vol. 48, No. 2, p. 221-228-- February 10, 2012 ...[Visit Journal]
Electrical and radiometric characterization results of a high-operability 1024 x 1024 long wavelength infrared type-II superlattice focal plane array are described. It demonstrates excellent quantum efficiency operability of 95.8% and 97.4% at operating temperatures of 81 K and 68 K, respectively. The external quantum efficiency is 81% without any antireflective coating. The dynamic range is 37 dB at 81 K and increases to 39 dB at 68 K operating temperature. The focal plane array has noise equivalent temperature difference as low as 27 mK and 19 mK at operating temperatures of 81 K and 68 K, respectively, using f/2 optics and an integration time of 0.13 ms. [reprint (PDF)]
 
3.  Ultrafast Pulse Generation from Quantum Cascade Lasers
Feihu Wang, Xiaoqiong Qi, Zhichao Chen, Manijeh Razeghi, and Sukhdeep Dhillon
Wang, F.; Qi, X.; Chen, Z.; Razeghi, M.; Dhillon, S. Ultrafast Pulse Generation from Quantum Cascade Lasers. Micromachines 2022, 13, 2063. https://doi.org/10.3390/ mi13122063 ...[Visit Journal]
Quantum cascade lasers (QCLs) have broken the spectral barriers of semiconductor lasers and enabled a range of applications in the mid-infrared (MIR) and terahertz (THz) regimes. However, until recently, generating ultrashort and intense pulses from QCLs has been difficult. This would be useful to study ultrafast processes in MIR and THz using the targeted wavelength-by-design properties of QCLs. Since the first demonstration in 2009, mode-locking of QCLs has undergone considerable development in the past decade, which includes revealing the underlying mechanism of pulse formation, the development of an ultrafast THz detection technique, and the invention of novel pulse compression technology, etc. Here, we review the history and recent progress of ultrafast pulse generation from QCLs in both the THz and MIR regimes. [reprint (PDF)]
 
3.  Quantum cascade lasers: from tool to product
M. Razeghi, Q. Y. Lu, N. Bandyopadhyay, W. Zhou, D. Heydari, Y. Bai, and S. Slivken
Optics Express Vol. 23, Issue 7, pp. 8462-8475-- March 25, 2015 ...[Visit Journal]
The quantum cascade laser (QCL) is an important laser source in the mid-infrared and terahertz frequency range. The past twenty years have witnessed its tremendous development in power, wall plug efficiency, frequency coverage and tunability, beam quality, as well as various applications based on QCL technology. Nowadays, QCLs can deliver high continuous wave power output up to 5.1 W at room temperature, and cover a wide frequency range from 3 to 300 μm by simply varying the material components. Broadband heterogeneous QCLs with a broad spectral range from 3 to 12 μm, wavelength agile QCLs based on monolithic sampled grating design, and on-chip beam QCL combiner are being developed for the next generation tunable mid-infrared source for spectroscopy and sensing. Terahertz sources based on nonlinear generation in QCLs further extend the accessible wavelength into the terahertz range. Room temperature continuous wave operation, high terahertz power up to 1.9 mW, and wide frequency tunability form 1 to 5 THz makes this type of device suitable for many applications in terahertz spectroscopy, imaging, and communication. [reprint (PDF)]
 
3.  Microstrip Array Ring FETs with 2D p-Ga2O3 Channels Grown by MOCVD
Manijeh Razeghi, Junhee Lee, Lakshay Gautam, Jean-Pierre Leburton, Ferechteh H. Teherani, Pedram Khalili Amiri, Vinayak P. Dravid and Dimitris Pavlidis
Photonics 2021, 8(12), 578; ...[Visit Journal]
Gallium oxide (Ga2O3) thin films of various thicknesses were grown on sapphire (0001) substrates by metal organic chemical vapor deposition (MOCVD) using trimethylgallium (TMGa), high purity deionized water, and silane (SiH4) as gallium, oxygen, and silicon precursors, respectively. N2 was used as carrier gas. Hall measurements revealed that films grown with a lower VI/III ratio had a dominant p-type conduction with room temperature mobilities up to 7 cm2/Vs and carrier concentrations up to ~1020 cm−3 for thinner layers. High resolution transmission electron microscopy suggested that the layers were mainly κ phase. Microstrip field-effect transistors (FETs) were fabricated using 2D p-type Ga2O3:Si, channels. They achieved a maximum drain current of 2.19 mA and an on/off ratio as high as ~108. A phenomenological model for the p-type conduction was also presented. As the first demonstration of a p-type Ga2O3, this work represents a significant advance which is state of the art, which would allow the fabrication of p-n junction based devices which could be smaller/thinner and bring both cost (more devices/wafer and less growth time) and operating speed (due to miniaturization) advantages. Moreover, the first scaling down to 2D device channels opens the prospect of faster devices and improved heat evacuation [reprint (PDF)]
 
2.  Buried heterostructure quantum cascade lasers with high continuous-wave wall plug efficiency
A. Evans, S.R. Darvish, S. Slivken, J. Nguyen, Y. Bai and M. Razeghi
Applied Physics Letters, Vol. 91, No. 7, p. 071101-1-- August 13, 2007 ...[Visit Journal]
The authors report on the development of ~4.7 µm strain-balanced InP-based quantum cascade lasers with high wall plug efficiency and room temperature continuous-wave operation. The use of narrow-ridge buried heterostructure waveguides and thermally optimized packaging is presented. Over 9.3% wall plug efficiency is reported at room temperature from a single device producing over 0.675 W of continuous-wave output power. Wall plug efficiencies greater than 18% are also reported for devices at a temperature of 150 K, with continuous-wave output powers of more than 1 W. [reprint (PDF)]
 
2.  Highly Conductive Co-Doped Ga2O3Si-In Grown by MOCVD
Junhee Lee, Honghyuk Kim, Lakshay Gautam and Manijeh Razeghi
Coatings 2021, 11(3), 287; https://doi.org/10.3390/coatings11030287 ...[Visit Journal]
We report a highly conductive gallium oxide doped with both silicon and indium grown on c-plane sapphire substrate by MOCVD. From a superlattice structure of indium oxide and gallium oxide doped with silicon, we obtained a highly conductive material with an electron hall mobility up to 150 cm2/V·s with the carrier concentration near 2 × 1017 cm−3. However, if not doped with silicon, both Ga2O3:In and Ga2O3 are highly resistive. Optical and structural characterization techniques such as X-ray, transmission electron microscope, and photoluminescence, reveal no significant incorporation of indium into the superlattice materials, which suggests the indium plays a role of a surfactant passivating electron trapping defect levels. [reprint (PDF)]
 
2.  Gain-length scaling in quantum dot/quantum well infrared photodetectors
T. Yamanaka, B. Movaghar, S. Tsao, S. Kuboya, A. Myzaferi and M. Razeghi
Virtual Journal of Nanoscale Science & Technology-- September 14, 2009 ...[Visit Journal][reprint (PDF)]
 
2.  Avalanche Photodetector Based on InAs/InSb Superlattice
Arash Dehzangi, Jiakai Li, Lakshay Gautam and Manijeh Razeghi
Quantum rep. 2020, 2(4), 591-599; https://doi.org/10.3390/quantum2040041 (registering DOI)-- December 4, 2020 ...[Visit Journal]
This work demonstrates a mid-wavelength infrared InAs/InSb superlattice avalanche photodiode (APD). The superlattice APD structure was grown by molecular beam epitaxy on GaSb substrate. The device exhibits a 100 % cut-off wavelength of 4.6 µm at 150 K and 4.30 µm at 77 K. At 150 and 77 K, the device responsivity reaches peak values of 2.49 and 2.32 A/W at 3.75 µm under −1.0 V applied bias, respectively. The device reveals an electron dominated avalanching mechanism with a gain value of 6 at 150 K and 7.4 at 77 K which was observed under −6.5 V bias voltage. The gain value was measured at different temperatures and different diode sizes. The electron and hole impact ionization coefficients were calculated and compared to give a better prospect of the performance of the device. [reprint (PDF)]
 
2.  Single-mode, high-power, midinfrared, quantum cascade laser phased arrays
Wenjia Zhou , Donghai Wu , Quan-Yong Lu, Steven Slivken & Manijeh Razeghi
Scientific Reports 8:14866-- October 5, 2018 ...[Visit Journal]
We demonstrate single-mode, 16-channel, optical phased arrays based on quantum cascade laser technology, with emission wavelengths around 4.8 μm. The integrated device consists of a distributed feedback seed section, a highly-efficient tree array multi-mode interferometer power splitter, and a 16-channel amplifier array with a 4° angled facet termination. With a single layer Y2O3 coating, the angled facet reflectivity is estimated to be less than 0.1% for suppressing amplifier self-lasing. A peak output power of 30 W is achieved with an emission spectrum narrower than 11 nm and a side mode suppression ratio over 25 dB. Far field distribution measurement result indicates a uniform phase distribution across the array output. Using the same phased array architecture, we also demonstrate single-mode 3.8 μm QCL amplifier arrays with up to 20 W output power. [reprint (PDF)]
 
2.  Photovoltaic MWIR type-II superlattice focal plane array on GaAs substrate
E.K. Huang, P.Y. Delaunay, B.M. Nguyen, S. Abdoullahi-Pour, and M. Razeghi
IEEE Journal of Quantum Electronics (JQE), Vol. 46, No. 12, p. 1704-1708-- December 1, 2010 ...[Visit Journal]
Recent improvements in the performance of Type-II superlattice (T2SL) photodetectors has spurred interest in developing low cost and large format focal plane arrays (FPA) on this material system. Due to the limitations of size and cost of native GaSb substrates, GaAs is an attractive alternative with 8” wafers commercially available, but is 7.8% lattice mismatched to T2SL. In this paper, we present a photovoltaic T2SL 320 x 256 focal plane array (FPA) in the MWIR on GaAs substrate. The FPA attained a median noise equivalent temperature difference (NEDT) of 13 mK and 10mK (F#=2.3) with integration times of 10.02 ms and 19.06 ms respectively at 67 K. [reprint (PDF)]
 
2.  Type-II ‘M’ Structure Photodiodes: An Alternative Material Design for Mid-Wave to Long Wavelength Infrared Regimes
B-M. Nguyen, M. Razeghi, V. Nathan, and G.J. Brown
SPIE Conference, January 25-29, 2007, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices IV, Vol. 6479, p. 64790S-1-10-- January 29, 2007 ...[Visit Journal]
In this work, an AlSb-containing Type-II InAs/GaSb superlattice, the so-called M-structure, is presented as a candidate for mid and long wavelength infrared detection devices. The effect of inserting an AlSb barrier in the GaSb layer is discussed and predicts many promising properties relevant to practical use. A good agreement between the theoretical calculation based on Empirical Tight Binding Method framework and experimental results is observed, showing the feasibility of the structure and its properties. A band gap engineering method without material stress constraint is proposed. [reprint (PDF)]
 
2.  Comparison of chemical and laser lift-off for the transfer of InGaN-based p-i-n junctions from sapphire to glass substrates
D. J. Rogers ; P. Bove ; F. Hosseini Teherani ; K. Pantzas ; T. Moudakir ; G. Orsal ; G. Patriarche ; S. Gautier ; A. Ougazzaden ; V. E. Sandana ; R. McClintock ; M. Razeghi
Proc. SPIE 8626, Oxide-based Materials and Devices IV, 862611 (March 18, 2013)-- March 18, 2013 ...[Visit Journal]
InGaN-based p-i-n structures were transferred from sapphire to soda-lime glass substrates using two approaches: (1) laser-lift-off (LLO) and thermo-metallic bonding and (2) chemical lift-off (LLO) by means sacrificial ZnO templates and direct wafer bonding. Both processes were found to function at RT and allow reclaim of the expensive single crystal substrate. Both approaches have also already been demonstrated to work for the wafer-scale transfer of III/V semiconductors. Compared with the industry-standard LLO, the CLO offers the added advantages of a lattice match to InGaN with higher indium contents, no need for an interfacial adhesive layer (which facilitates electrical, optical and thermal coupling), no damaged/contaminated GaN surface layer, simplified sapphire reclaim (GaN residue after LLO may complicate reclaim) and cost savings linked to elimination of the expensive LLO process. [reprint (PDF)]
 

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