Center for Quantum Devices - Most Downloaded Journal Articles

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3.	High-performance short-wavelength infrared photodetectors based on type-II InAs/InAs1-xSbx/AlAs1-xSbx superlattices A. Haddadi, X.V. Suo, S. Adhikary, P. Dianat, R. Chevallier, A.M. Hoang, and M. Razeghi Applied Physics Letters 107 , 141104-- October 5, 2015 ...[Visit Journal] A high-performance short-wavelength infrared n-i-p photodiode based on InAs/InAs1-xSbx/AlAs1-xSbx type-II superlattices on GaSb substrate has been demonstrated. The device is designed to have a 50% cut-off wavelength of ~1.8μm at 300K. The photodetector exhibited a room-temperature (300 K) peak responsivity of 0.47 A/W at 1.6μm, corresponding to a quantum efficiency of 37% at zero bias under front-side illumination, without any anti-reflection coating. With an R×A of 285 Ω·cm² and a dark current density of 9.6×10^-5 A/cm² under −50mV applied bias at 300 K, the photodiode exhibited a specific detectivity of 6.45×10¹⁰ cm·Hz^½/W. At 200 K, the photodiode exhibited a dark current density of 1.3×10^-8 A/cm² and a quantum efficiency of 36%, resulting in a detectivity of 5.66×10¹² cm·Hz^½/W. [reprint (PDF)]
3.	Al_xGa_1−xN-based solar-blind ultraviolet photodetector based on lateral epitaxial overgrowth of AlN on Si substrate E. Cicek, R. McClintock, C. Y. Cho, B. Rahnema, and M. Razeghi Appl. Phys. Lett. 103, 181113 (2013)-- October 30, 2013 ...[Visit Journal] We report on Al_xGa_1−xN-based solar-blind ultraviolet (UV) photodetector (PD) grown on Si(111) substrate. First, Si(111) substrate is patterned, and then metalorganic chemical vapor deposition is implemented for a fully-coalesced ∼8.5 μm AlN template layer via a pulsed atomic layer epitaxial growth technique. A back-illuminated p-i-n PD structure is subsequently grown on the high quality AlN template layer. After processing and implementation of Si(111) substrate removal, the optical and electrical characteristic of PDs are studied. Solar-blind operation is observed throughout the array; at the peak detection wavelength of 290 nm, 625 μm² area PD showed unbiased peak external quantum efficiency and responsivity of ∼7% and 18.3 mA/W, respectively, with a UV and visible rejection ratio of more than three orders of magnitude. Electrical measurements yielded a low-dark current density below 1.6 × 10⁻⁸ A/cm² at 10 V reverse bias. [reprint (PDF)]
3.	High performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices A.M. Hoang, G. Chen, A. Haddadi and M. Razeghi SPIE Proceedings, Vol. 8631, p. 86311K-1, Photonics West, San Francisco, CA-- February 5, 2013 ...[Visit Journal] Active and passive imaging in a single camera based on the combination of short-wavelength and mid-wavelength infrared detection is highly needed in a number of tracking and reconnaissance missions. Due to its versatility in band-gap engineering, Type-II InAs/GaSb/AlSb superlattice has emerged as a candidate highly suitable for this multi-spectral detection. In this paper, we report the demonstration of high performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 μm and 4 μm. Taking advantages of the high performance short-wavelength and mid-wavelength single color photodetectors, back-to-back p-i-n-n-i-p photodiode structures were grown on GaSb substrate by molecular beam epitaxy. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0x10^-9 A/cm² at -50 mV bias voltage, providing an associated shot noise detectivity of 3.0x10¹³ Jones. The mid-wavelength channel exhibited a quantum efficiency of 33% and a dark current density of 2.6x10^-5 A/cm² at 300 mV bias voltage, resulting in a detectivity of 4.0x10¹¹ Jones. The operations of the two absorber channels are selectable by changing the polarity of applied bias voltage. [reprint (PDF)]
3.	Surface leakage current reduction in long wavelength infrared type-II InAs/GaSb superlattice photodiodes S. Bogdanov, B.M. Nguyen, A.M. Hoang, and M. Razeghi Applied Physics Letters, Vol. 98, No. 18, p. 183501-1-- May 2, 2011 ...[Visit Journal] Dielectric passivation of long wavelength infrared Type-II InAs/GaSb superlattice photodetectors with different active region doping profiles has been studied. SiO₂ passivation was shown to be efficient as long as it was not put in direct contact with the highly doped superlattice. A hybrid graded doping profile combined with the shallow etch technique reduced the surface leakage current in SiO₂ passivated devices by up to two orders of magnitude compared to the usual design. As a result, at 77 K the SiO(2) passivated devices with 10.5 μm cutoff wavelength exhibit an R₀A of 120 Ω·cm², R_maxA of 6000 Ω·cm², and a dark current level of 3.5×10⁻⁵ A·cm⁻² at −50 mV bias. [reprint (PDF)]
3.	Room temperature continuous wave operation of quantum cascade lasers with watt-level optical power Y. Bai, S.R. Darvish, S. Slivken, W. Zhang, A. Evans, J. Nguyen and M. Razeghi Applied Physics Letters, Vol. 92, No. 10, p. 101105-1-- March 10, 2008 ...[Visit Journal] We demonstrate quantum cascade lasers at an emitting wavelength of 4.6 µm, which are capable of room temperature, high power continuous wave (cw) operation. Buried ridge geometry with a width of 9.8 µm was utilized. A device with a 3 mm cavity length that was epilayer-down bonded on a diamond submount exhibited a maximum output power of 1.3 W at room temperature in cw operation. The maximum output power at 80 K was measured to be 4 W, with a wall plug efficiency of 27%. [reprint (PDF)]
3.	Polarity inversion of Type-II InAs/GaSb superlattice photodiodes B.M. Nguyen, D. Hoffman, P.Y. Delaunay, M. Razeghi and V. Nathan Applied Physics Letters, Vol. 91, No. 10, p. 103503-1-- September 3, 2007 ...[Visit Journal] The authors demonstrated the realization of p-on-n Type-II InAs/GaSb superlattice photodiodes. Growth condition for high quality InAsSb layer lattice matched to GaSb was established for the use of an effective n-contact layer. By studying the effect of various GaSb capping layer thicknesses on the optical and electrical performances, an optimized thickness of 160 nm was determined. In comparison to as grown n-on-p superlattice photodiodes, this inverted design of p on n has shown similar quality. Finally, by analyzing Fabry-Perot interference fringes in the front side illuminated spectral measurement, the refractive index of the superlattice was determined to be approximately 3.8. [reprint (PDF)]
3.	Demonstration of mid-wavelength infrared nBn photodetectors based on type-II InAs/InAs_1-xSb_x superlattice grown by metal-organic chemical vapor deposition Donghai Wu, Arash Dehzangi, and Manijeh Razeghi Appl. Phys. Lett. 115, 061102-- August 6, 2019 ...[Visit Journal] We report design, growth, and characterization of midwavelength infrared nBn photodetectors based on a type-II InAs/InAs_1-xSb_x superlattice on a GaSb substrate grown by metal-organic chemical vapor deposition. An InAs/AlAs_1-ySb_y/InAs/InAs_1-xSb_x superlattice design was used as the large bandgap electron barrier in the photodetectors. At 150 K, the photodetector exhibits a peak responsivity of 1.23 A/W, corresponding to a quantum efficiency of 41% at an applied bias voltage of −100 mV under front-side illumination, with a 50% cut-off wavelength of 4.6 μm. With an R × A of 356 Ω·cm² and a dark current density of 1.6 × 10⁻⁴ A/cm² under an applied bias of −100 mV at 150 K, the photodetector exhibits a specific detectivity of 1.4 × 10¹¹ cm·Hz^1/2/W. [reprint (PDF)]
3.	High Performance Solar-Blind Ultraviolet Focal Plane Arrays Based on AlGaN Erdem Cicek, Ryan McClintock, Abbas Haddadi, William A. Gaviria Rojas, and Manijeh Razeghi IEEE Journal of Quantum Electronics, Vol. 50, Issue 8, p 591-595-- August 1, 2014 ...[Visit Journal] We report on solar-blind ultraviolet, AlxGa1-x N- based,p-i-n,focal plane array (FPA) with 92% operability. At the peak detection wavelength of 278 nm, 320×256-FP A-pixel showed unbiased peak external quantum efficiency (EQE) and responsivity of 49% and 109 mA/W, respectively, increasing to 66% under 5 volts of reverse bias. Electrical measurements yielded a low-dark current density: <7×10^-9A/cm², at FPA operating voltage of 2 volts of reverse bias. [reprint (PDF)]
3.	Crack-free AlGaN for solar-blind focal plane arrays through reduced area expitaxy E. Cicek, R. McClintock, Z. Vashaei, Y. Zhang, S. Gautier, C.Y. Cho and M. Razeghi Applied Physics Letters, Vol. 102, No. 05, p. 051102-1-- February 4, 2013 ...[Visit Journal] We report on crack reduction for solar-blind ultraviolet detectors via the use of a reduced area epitaxy (RAE) method to regrow on patterned AlN templates. With the RAE method, a pre-deposited AlN template is patterned into isolated mesas in order to reduce the formation of cracks in the subsequently grown high Al-content Al_xGa_1−xN structure. By restricting the lateral dimensions of the epitaxial growth area, the biaxial strain is relaxed by the edges of the patterned squares, which resulted in ∼97% of the pixels being crack-free. After successful implementation of RAE method, we studied the optical characteristics, the external quantum efficiency, and responsivity of average pixel-sized detectors of the patterned sample increased from 38% and 86.2 mA/W to 57% and 129.4 mA/W, respectively, as the reverse bias is increased from 0 V to 5 V. Finally, we discussed the possibility of extending this approach for focal plane array, where crack-free large area material is necessary for high quality imaging. [reprint (PDF)]
3.	Thermal Conductivity of InAs/GaSb Type II Superlattice C. Zhou, B.M. Nguyen, M. Razeghi and M. Grayson Journal of Electronic Materials, Vol. 41, No. 9, p. 2322-2325-- August 1, 2012 ...[Visit Journal] The cross-plane thermal conductivity of a type II InAs/GaSb superlattice(T2SL) is measured from 13 K to 300 K using the 3x method. Thermal conductivity is reduced by up to two orders of magnitude relative to the GaSb bulk substrate. The low thermal conductivity of around 1 W/m K to 8 W/m K may serve as an advantage for thermoelectric applications at low temperatures, while presenting a challenge for T2SL interband cascade lasers and highpower photodiodes. We describe a power-law approximation to model nonlinearities in the thermal conductivity, resulting in increased or decreased peak temperature for negative or positive exponents, respectively. [reprint (PDF)]
3.	Demonstration of high performance long wavelength infrared Type-II InAs/GaSb superlattice photodidoe grown on GaAs substrate S. Abdollahi Pour, B.M. Nguyen, S. Bogdanov, E.K. Huang, and M. Razeghi Applied Physics Letters, Vol. 95, No. 17, p. 173505-- October 26, 2009 ...[Visit Journal] We report the growth and characterization of long wavelength infrared type-II InAs/GaSb superlattice photodiodes with a 50% cut-off wavelength at 11 µm, on GaAs substrate. Despite a 7.3% lattice mismatch to the substrate, photodiodes passivated with polyimide exhibit an R₀A value of 35 Ω·cm² at 77 K, which is in the same order of magnitude as reference devices grown on native GaSb substrate. With a reverse applied bias less than 500 mV, the dark current density and differential resistance-area product are close to that of devices on GaSb substrate, within the tolerance of the processing and measurement. The quantum efficiency attains the expected value of 20% at zero bias, resulting in a Johnson limited detectivity of 1.1×10¹¹ Jones. Although some difference in performances is observed, devices grown on GaAs substrate already attained the background limit performance at 77 K with a 300 K background and a 2-π field of view. [reprint (PDF)]
3.	Room-temperature, high-power and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ ~ 9.6 µm S.R. Darvish, S. Slivken, A. Evans, J.S. Yu, and M. Razeghi Applied Physics Letters, 88 (20)-- May 15, 2006 ...[Visit Journal] High-power continuous-wave (cw) operation of distributed-feedback quantum-cascade lasers is reported. Continuous-wave output powers of 100 mW at 25 °C and 20 mW at 50 °C are obtained. The device exhibits a cw threshold current density of 1.34 kA/cm², a maximum cw wall-plug efficiency of 1% at 25 °C, and a characteristic temperature of ~190 K in pulsed mode. Single-mode emission near 9.6 μm with a side-mode suppression ratio of ≥ 30 dB and a tuning range of 2.89 cm^–1 from 15 to 50 °C is obtained. [reprint (PDF)]
3.	Suppressing Spectral Crosstalk in Dual-Band LongWavelength Infrared Photodetectors With Monolithically Integrated Air-Gapped Distributed Bragg Reﬂectors Yiyun Zhang, Abbas Haddadi, Arash Dehzangi , Romain Chevallier, Manijeh Razeghi IEEE Journal of Quantum Electronics Volume: 55, Issue:1-- November 22, 2018 ...[Visit Journal] Antimonide-based type-II superlattices (T2SLs) have made possible the development of high-performance infrared cameras for use in a wide variety of thermal imaging applications, many of which could beneﬁt from dual-band imaging. The performance of this material system has not reached its limits. One of the key issues in dual-band infrared photodetection is spectral crosstalk. In this paper, air-gapped distributed Bragg reﬂectors (DBRs) have been monolithically integrated between the two channels in long-/very long-wavelength dualband InAs/InAs_1−xSb_x/AlAs_1−xSb_x-based T2SLs photodetectors to suppress the spectral crosstalk. This air-gapped DBR has achieved a signiﬁcant spectral suppression in the 4.5–7.5-µm photonic stopband while transmitting the optical wavelengths beyond 7.5 µm, which is conﬁrmed by theoretical calculations, numerical simulation, and experimental results. [reprint (PDF)]
3.	Direct growth of thick AlN layers on nanopatterned Si substrates by cantilever epitaxy Ilkay Demir, Yoann Robin, Ryan McClintock, Sezai Elagoz, Konstantinos Zekentes, and Manijeh Razeghi Phys. Status Solidi A, pp. 1–6-- September 30, 2016 ...[Visit Journal] AlN layers have been grown on 200 nm period of nanopatterned Si (111) substrates by cantilever epitaxy and compared with AlN layers grown by maskless lateral epitaxial overgrowth (LEO) on micropatterned Si (111) substrates. The material quality of 5–10 µm thick AlN grown by LEO is comparable to that of much thinner layers (2 µm) grown by cantilever epitaxy on the nanopatterned substrates. Indeed, the latter exhibited root mean square (RMS) roughness of 0.65 nm and X-ray diffraction full width at half-maximum (FWHM) of 710 arcsec along the (0002) reflection and 930 arcsec along the (10̅15) reflection. The corresponding room temperature photoluminescence spectra was dominated by a sharp band edge peak. Back emission ultra violet light emitting diodes (UV LEDs) were fabricated by flip chip bonding to patterned AlN heat sinks followed by complete Si (111) substrate removal demonstrating a peak pulsed power of ∼0.7 mW at 344 nm peak emission wavelength. The demonstrated UV LEDs were fabricated on a cost effective epitaxial structure grown on the nanopatterned Si substrate with a total thickness of 3.3 µm [reprint (PDF)]
3.	High operability 1024 x 1024 long wavelength infrared focal plane array base on Type-II InAs/GaSb superlattice A. Haddadi, S.R. Darvish, G. Chen, A.M. Hoang, B.M. Nguyen and M. Razeghi AIP Conference Proceedings, Vol. 1416, p. 56-58_NGS15 Conf_Blacksburg, VA_Aug 1-5, 2011-- December 31, 2011 ...[Visit Journal] Fabrication and characterization of a high performance 1024×1024 long wavelength infrared type‐II superlattice focal plane array are described. The FPA performs imaging at a continous rate of 15.00 frames/sec. Each pixel has pitch of 18μm with a fill factor of 71.31%. It demonstrates excellent operability of 95.8% and 97.4% at 81 and 68K operation temperature. The external quantum efficiency is ∼81% without any antireflective coating. Using F∕2 optics and an integration time of 0.13ms, the FPA exhibits an NEDT as low as 27 and 19mK at operating temperatures of 81 and 68K respectively. [reprint (PDF)]
3.	High operating temperature MWIR photon detectors based on Type II InAs/GaSb superlattice M. Razeghi, S. Abdollahi Pour, E.K. Huang, G. Chen, A. Haddadi and B.M. Nguyen SPIE Proceedings, Infrared Technology and Applications XXXVII, Orlando, FL, Vol. 8012, p. 80122Q-1-- April 26, 2011 ...[Visit Journal] Recent efforts have been paid to elevate the operating temperature of Type II superlattice Mid Infrared photon detectors. Using M-structure superlattice, novel device architectures have been developed, resulting in significant improvement of the device performances. In this paper, we will compare different photodetector architectures and discuss the optimization scheme which leads to almost one order of magnitude of improvement to the electrical performance. At 150K, single element detectors exhibit a quantum efficiency above 50%, and a specific detectivity of 1.05x10(12) cm.Hz(1/2)/W. BLIP operation with a 300K background and 2π FOV can be reached with an operating temperature up to 180K. High quality focal plane arrays were demonstrated with a noise equivalent temperature difference (NEDT) of 11mK up to 120K. Human body imaging is achieved at 150K with NEDT of 150mK. [reprint (PDF)]
3.	Quantum cascade lasers that emit more light than heat Y. Bai, S. Slivken, S. Kuboya, S.R. Darvish and M. Razeghi Nature Photonics, February 2010, Vol. 4, p. 99-102-- February 1, 2010 ...[Visit Journal] For any semiconductor lasers, the wall plug efficiency, that is, the portion of the injected electrical energy that can be converted into output optical energy, is one of the most important figures of merit. A device with a higher wall plug efficiency has a lower power demand and prolonged device lifetime due to its reduced self-heating. Since its invention, the power performance of the quantum cascade laser has improved tremendously. However, although the internal quantum efficiency can be engineered to be greater than 80% at low temperatures, the wall plug efficiency of a quantum cascade laser has never been demonstrated above 50% at any temperature. The best wall plug efficiency reported to date is 36% at 120 K. Here, we overcome the limiting factors using a single-well injector design and demonstrate 53% wall plug efficiency at 40 K with an emitting wavelength of 5 µm. In other words, we demonstrate a quantum cascade laser that produces more light than heat. [reprint (PDF)]
3.	A hybrid green light-emitting diode comprised of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN C. Bayram, F. Hosseini Teherani, D.J. Rogers and M. Razeghi Applied Physics Letters, Vol. 93, No. 8, p. 081111-1-- August 25, 2008 ...[Visit Journal] Hybrid green light-emitting diodes (LEDs) comprised of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN were grown on semi-insulating AlN/sapphire using pulsed laser deposition for the n-ZnO and metal organic chemical vapor deposition for the other layers. X-ray diffraction revealed that high crystallographic quality was preserved after the n-ZnO growth. LEDs showed a turn-on voltage of 2.5 V and a room temperature electroluminescence (EL) centered at 510 nm. A blueshift and narrowing of the EL peak with increasing current was attributed to bandgap renormalization. The results indicate that hybrid LED structures could hold the prospect for the development of green LEDs with superior performance. [reprint (PDF)]
3.	Broadband monolithically-tunable quantum cascade lasers Wenjia Zhou, Ryan McClintock, Donghai Wu, Steven Slivken, Manijeh Razeghi Proc. SPIE 10540, Quantum Sensing and Nano Electronics and Photonics XV, 105400A-- January 26, 2018 ...[Visit Journal] Mid-infrared lasers, emitting in the spectral region of 3-12 μm that contain strong characteristic vibrational transitions of many important molecules, are highly desirable for spectroscopy sensing applications. High efficiency quantum cascade lasers have been demonstrated with up to watt-level output power in the mid-infrared region. However, the wide wavelength tuning, which is critical for spectroscopy applications, is still largely relying on incorporating external gratings, which have stability issues. Here, we demonstrate the development a monolithic, widely tunable quantum cascade laser source emitting between 6.1 and 9.2 μm through an on-chip integration of a sampled grating distributed feedback tunable laser array with a beam combiner. A compact tunable laser system was built to drive the individual lasers within the array and coordinate the driving of the laser array to produce desired wavelength. A broadband spectral measurement (520cm^-1) of methane shows excellent agreement with Fourier transform infrared spectrometer measurement. Further optimizations have led to high performance monolithic tunable QCLs with up to 65 mW output while delivering fundamental mode outputs. [reprint (PDF)]
3.	Radiometric characterization of long-wavelength infrared type II strained layer superlattice focal plane array under low-photon irradiance conditions J. Hubbs, V. Nathan, M. Tidrow, and M. Razeghi Optical Engineering, Vol. 51, No. 6, p. 064002-1-- June 15, 2012 ...[Visit Journal] We present the results of the radiometric characterization of an “M” structure long wavelength infrared Type-II strained layer superlattice(SLS) infrared focal plane array (IRFPA) developed by Northwestern University (NWU). The performance of the M-structure SLS IRFPA was radiometrically characterized as a function of photon irradiance, integration time, operating temperature, and detector bias. Its performance is described using standard figures of merit: responsivity, noise, and noise equivalent irradiance. Assuming background limited performance operation at higher irradiances, the detector quantum efficiency for the SLS detector array is approximately 57%. The detector dark density at 80 K is 142 μA∕cm², which represents a factor of seven reduction from previously measured devices. [reprint (PDF)]
3.	Reliability in room-temperature negative differential resistance characteristics of low-aluminum contact AlGaN/GaN double-barrier resonant tunneling diodes C. Bayram, Z. Vashaei, and M. Razeghi Applied Physics Letters, Vol. 97, No. 18, p. 181109-1-- November 1, 2010 ...[Visit Journal] AlGaN/GaN resonant tunneling diodes (RTDs), consisting of 20% (10%) aluminum-content in double-barrier (DB) active layer, were grown by metal-organic chemical vapor deposition on freestanding polar (c-plane) and nonpolar (m-plane) GaN substrates. RTDs were fabricated into 35-μm-diameter devices for electrical characterization. Lower aluminum content in the DB active layer and minimization of dislocations and polarization fields increased the reliability and reproducibility of room-temperature negative differential resistance (NDR). Polar RTDs showed decaying NDR behavior, whereas nonpolar ones did not significantly. Averaging over 50 measurements, nonpolar RTDs demonstrated a NDR of 67 Ω, a current-peak-to-valley ratio of 1.08, and an average oscillator output power of 0.52 mW. [reprint (PDF)]
3.	Material and design engineering of (Al)GaN for high-performance avalanche photodiodes and intersubband applications M. Razeghi and C. Bayram SPIE Proceedings, Dresden, Germany (May 4-6, 2009), Vol. 7366, p. 73661F-1-- May 20, 2009 ...[Visit Journal] Numerous applications in scientific, medical, and military areas demand robust, compact, sensitive, and fast ultraviolet (UV) detection. Our (Al)GaN photodiodes pose high avalanche gain and single-photon detection efficiency that can measure up to these requirements. Inherit advantage of back-illumination in our devices offers an easier integration and layout packaging via flip-chip hybridization for UV focal plane arrays that may find uses from space applications to hostile-agent detection. Thanks to the recent (Al)GaN material optimization, III-Nitrides, known to have fast carrier dynamics and short relaxation times, are employed in (Al)GaN based superlattices that absorb in near-infrared regime. In this work, we explain the origins of our high performance UV APDs, and employ our (Al)GaN material knowledge for intersubband applications. We also discuss the extension of this material engineering into the far infrared, and even the terahertz (THz) region. [reprint (PDF)]
3.	Type-II Superlattices and Quantum Cascade Lasers for MWIR and LWIR Free-Space Communications A. Hood, A. Evans and M. Razeghi SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 690005-1-9.-- February 1, 2008 ...[Visit Journal] Free-space optical communications has recently been touted as a solution to the "last mile" bottleneck of high-speed data networks providing highly secure, short to long range, and high-bandwidth connections. However, commercial near infrared systems experience atmospheric scattering losses and scintillation effects which can adversely affect a link's operating budget. By moving the operating wavelength into the mid- or long-wavelength infrared enhanced link uptimes and increased operating range can be achieved due to less susceptibility to atmospheric affects. The combination of room-temperature, continuous-wave, high-power quantum cascade lasers and high operating temperature type-II superlattice photodetectors offers the benefits of mid- and long-wavelength infrared systems as well as practical operating conditions for next generation free-space communications systems. [reprint (PDF)]
3.	High Power, Continuous-Wave, Quantum Cascade Lasers for MWIR and LWIR Applications S. Slivken, A. Evans, J.S. Yu, S.R. Darvish and M. Razeghi SPIE Conference, San Jose, CA, Vol. 6127, pp. 612703-- January 23, 2006 ...[Visit Journal] Over the past several years, our group has endeavored to develop high power quantum cascade lasers for a variety of remote and high sensitivity infrared applications. The systematic optimization of laser performance has allowed for demonstration of high power, continuous-wave quantum cascade lasers operating above room temperature. Since 2002, the power levels for individual devices have jumped from 20 mW to 600 mW. Expanding on this development, we have able to demonstrate continuous wave operation at many wavelengths throughout the mid- and far-infrared spectral range, and have now achieved >100 mW output in the 4.0 to 9.5 µm range. [reprint (PDF)]
3.	Negative and positive luminescence in mid-wavelength infrared InAs/GaSb superlattice photodiodes D. Hoffman, A. Gin, Y. Wei, A. Hood, F. Fuchs, and M. Razeghi IEEE Journal of Quantum Electronics, 41 (12)-- December 1, 2005 ...[Visit Journal] The quantum efficiency of negative and positive luminescence in binary type-II InAs-GaSb superlattice photodiodes has been investigated in the midinfrared spectral range around the 5-μm wavelength. The negative luminescence efficiency is nearly independent on temperature in the entire range from 220 to 325 K. For infrared diodes with a 2-μm absorbing layer, processed without anti-reflection coating, a negative luminescence efficiency of 45% is found, indicating very efficient minority carrier extraction. The temperature dependent measurements of the quantum efficiency of the positive luminescence enables for the determination of the capture cross section of the Shockley-Read-Hall centers involved in the competing nonradiative recombination. [reprint (PDF)]

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