Center for Quantum Devices - Most Downloaded Journal Articles

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1.	Advanced InAs/GaSb Superlattice Photovoltaic Detectors for Very-Long Wavelength Infrared Applications Y. Wei, A. Gin, M. Razeghi, and G.J. Brown Applied Physics Letters 80 (18)-- May 6, 2002 ...[Visit Journal] We report on the temperature dependence of the photoresponse of very long wavelength infrared type-II InAs/GaSb superlattice based photovoltaic detectors grown by molecular-beam epitaxy. The detectors had a 50% cutoff wavelength of 18.8 μm and a peak current responsivity of 4 A·W^-1 at 80 K. A peak detectivity of 4.5×10¹⁰ cm· Hz^½·W^-1 was achieved at 80 K at a reverse bias of 110 mV. The generation–recombination lifetime was 0.4 ns at 80 K. The cutoff wavelength increased very slowly with increasing temperature with a net shift from 20 to 80 K of only 1.2 μm [reprint (PDF)]
1.	Watt level performance of quantum cascade lasers in room temperature continuous wave operation at λ ∼ 3.76 μm N. Bandyopadhyay, Y. Bai, B. Gokden, A. Myzaferi, S. Tsao, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 97, No. 13-- September 27, 2010 ...[Visit Journal] An InP-based quantum cascade laser heterostructure emitting at 3.76 μm is grown with gas-source molecular beam epitaxy. The laser core is composed of strain balanced In_0.76Ga_0.24As/In_0.26Al_0.74As. Pulsed testing at room temperature exhibits a low threshold current density (1.5 kA/cm²) and high wall plug efficiency (10%). Room temperature continuous wave operation gives 6% wall plug efficiency with a maximum output power of 1.1 W. Continuous wave operation persists up to 95 °C. [reprint (PDF)]
1.	Beam Steering in High-Power CW Quantum Cascade Lasers W.W. Bewley, J.R. Lindle, C.S. Kim, I. Vurgaftman, J.R. Meyer, A.J. Evans, J.S. Yu, S. Slivken, and M. Razeghi IEEE Journal of Quantum Electronics, 41 (6)-- June 1, 2005 ...[Visit Journal] We report the light-current (L-I), spectral, and far-field characteristics of quantum cascade lasers (QCLs) with seven different wavelengths in the λ=4.3 to 6.3 μm range. In continuous-wave (CW) mode, the narrow-stripe (≈13 μm) epitaxial- side-up devices operated at temperatures up to 340 K, while at 295 K the CW output power was as high as 640 mW with a wallplug efficiency of 4.5%. All devices with λ≥4.7 μm achieved room-temperature CW operation, and at T=200 K several produced powers exceeding 1 W with ≈10% wallplug efficiency. The data indicated both spectral and spatial instabilities of the optical modes. For example, minor variations of the current often produced nonmonotonic hopping between spectra with envelopes as narrow as 5-10 nm or as broad as 200-250 nm. Bistable beam steering, by far-field angles of up to ±12° from the facet normal, also occurred, although even in extreme cases the beam quality never became worse than twice the diffraction limit. The observed steering is consistent with a theory for interference and beating between the two lowest order lateral modes. We also describe simulations of a wide-stripe photonic-crystal distributed-feedback QCL, which based on the current material quality is projected to emit multiple watts of CW power into a single-mode beam at T=200 K. [reprint (PDF)]
1.	Intersubband hole absorption in GaAs-GaInP Quantum Wells grown by Gas Source Molecular Beam Epitaxy J. Hoff, C. Jelen, S. Slivken, E. Michel, O. Duchemin, E. Bigan, and M. Razeghi with G. Brown and S.M. Hegde (Wright Laboratory) Applied Physics Letters 65 (9)-- August 29, 1994 ...[Visit Journal] P-doped GaAs‐GaInP quantum wells have been grown on GaAs substrate by gas source molecular beam epitaxy. Structural quality has been evidenced by x-ray diffraction. A narrow low-temperature photoluminescence full width at half‐maximum has been measured. Strong hole intersubband absorption has been observed at 9 μm, and its dependence on light polarization has been investigated. [reprint (PDF)]
1.	Near bulk-limited R0A of long-wavelength infrared type-II InAs/GaSb superlattice photodiodes with polyimide surface passivation Andrew Hood, Pierre-Yves Delaunay, Darin Hoffman, Binh-Minh Nguyen, Yajun Wei, Manijeh Razeghi, and Vaidya Nathan Applied Physics Letters 90, 233513-- June 4, 2007 ...[Visit Journal] Effective surface passivation of Type-II InAs/GaSb superlattice photodiodes with cutoff wavelengths in the long-wavelength infrared is presented. A stable passivation layer, the electrical properties of which do not change as a function of the ambient environment nor time, has been prepared by a solvent-based surface preparation, vacuum desorption, and the application of an insulating polyimide layer. Passivated photodiodes, with dimensions ranging from 400×400 to 25×25 µm², with a cutoff wavelength of ~11 µm, exhibited near bulk-limited R₀A values of ~12 Ω·cm², surface resistivities in excess of 10⁴ Ω·cm, and very uniform current-voltage behavior at 77 K. [reprint (PDF)]
1.	High-power high-wall plug efficiency mid-infrared quantum cascade lasers based on InP/GaInAs/InAlAs material system M. Razeghi SPIE Proceedings, San Jose, CA Volume 7230-11-- January 26, 2009 ...[Visit Journal] The latest result at the Center for Quantum Devices about high power, high wall plug efficiency, mid-infrared quantum cascade lasers (QCLs) is presented. At an emitting wavelength of 4.8 µm, an output power of 3.4 W and a wall plug efficiency of 16.5% are demonstrated from a single device operating in continuous wave at room temperature. At a longer wavelength of 10.2 µm, average power as high as 2.2 W is demonstrated at room temperature. Gas-source molecular beam epitaxy is used to grow the QCL core in an InP/GaInAs/InAlAs material system. Fe-doped semiinsulating regrowth is performed by metal organic chemical vapor deposition for efficient heat removal and low waveguide loss. This accomplishment marks an important milestone in the development of high performance midinfrared QCLs. [reprint (PDF)]
1.	Dark current reduction in microjunction-based double electron barrier type-II InAs/InAsSb superlattice long-wavelength infrared photodetectors Romain Chevallier, Abbas Haddadi, & Manijeh Razeghi Scientific Reports 7, Article number: 12617-- October 3, 2017 ...[Visit Journal] Microjunction InAs/InAsSb type-II superlattice-based long-wavelength infrared photodetectors with reduced dark current density were demonstrated. A double electron barrier design was employed to reduce both bulk and surface dark currents. The photodetectors exhibited low surface leakage after passivation with SiO2, allowing the use of very small size features without degradation of the dark current. Fabricating microjunction photodetectors (25 × 25 µm² diodes with 10 × 10 µm² microjunctions) in combination with the double electron barrier design results in a dark current density of 6.3 × 10⁻⁶ A/cm² at 77 K. The device has an 8 µm cut-off wavelength at 77 K and exhibits a quantum efficiency of 31% for a 2 µm-thick absorption region, which results in a specific detectivity value of 1.2 × 10¹² cm·Hz^½/W. [reprint (PDF)]
1.	Phase-locked, high power, mid-infrared quantum cascade laser array W. Zhou, S. Slivken, and M. Razeghi Applied Physics Letters 112, 181106-- May 4, 2018 ...[Visit Journal] We demonstrate phase-locked, high power quantum cascade laser arrays, which are combined using a monolithic, tree array multimode interferometer, with emission wavelengths around 4.8 μm. A maximum output power of 15 W was achieved from an eight-element laser array, which has only a slightly higher threshold current density and a similar slope efficiency compared to a Fabry-Perot laser of the same length. Calculated multimode interferometer splitting loss is on the order of 0.27 dB for the in-phase supermode. In-phase supermode operation with nearly ideal behavior is demonstrated over the working current range of the array. [reprint (PDF)]
1.	Short Wavelength (λ~ 4.3 μm) High-Performance Continuous-Wave Quantum-Cascade Lasers J.S. Yu, A. Evans, S. Slivken, S.R. Darvish, and M. Razeghi IEEE Photonics Technology Letters, 17 (6)-- June 1, 2005 ...[Visit Journal] We report continuous-wave (CW) operation of a 4.3-μm quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-μm-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm² is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 μm at 80 K to 4.34 μm at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26° and 49° in CW mode, respectively. [reprint (PDF)]
1.	QEPAS based ppb-level detection of CO and N₂O using a high power CW DFB-QCL Y. Ma, R. Lewicki, M. Razeghi and F. Tittel Optics Express, Vol. 21, No. 1, p. 1008-- January 14, 2013 ...[Visit Journal] An ultra-sensitive and selective quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor platform was demonstrated for detection of carbon monoxide (CO) and nitrous oxide (N₂O). This sensor used a stateof-the art 4.61 μm high power, continuous wave (CW), distributed feedback quantum cascade laser (DFB-QCL) operating at 10°C as the excitation source. For the R(6) CO absorption line, located at 2169.2 cm⁻¹, a minimum detection limit (MDL) of 1.5 parts per billion by volume (ppbv) at atmospheric pressure was achieved with a 1 sec acquisition time and the addition of 2.6% water vapor concentration in the analyzed gas mixture. For the N₂O detection, a MDL of 23 ppbv was obtained at an optimum gas pressure of 100 Torr and with the same water vapor content of 2.6%. In both cases the presence of water vapor increases the detected CO and N₂O QEPAS signal levels as a result of enhancing the vibrational-translational relaxation rate of both target gases. Allan deviation analyses were performed to investigate the long term performance of the CO and N2O QEPAS sensor systems. For the optimum data acquisition time of 500 sec a MDL of 340 pptv and 4 ppbv was obtained for CO and N₂O detection,respectively. To demonstrate reliable and robust operation of the QEPAS sensor a continuous monitoring of atmospheric CO and N₂O concentration levels for a period of 5 hours were performed. [reprint (PDF)]
1.	Sb-based third generation at Center for Quantum Devices Razeghi, Manijeh SPIE Proceedings Volume 11407, Infrared Technology and Applications XLVI; 114070T-- April 23, 2020 ...[Visit Journal] Sb-based III-V semiconductors are a promising alternative to HgCdTe. They can be produced with a similar bandgap to HgCdTe, but take advantage of the strong bonding between group III and group V elements which leads to very stable materials, good radiation hardness, and high uniformity. In this paper, we will discuss the recent progress of our research and present the main contributions of the Center for Quantum Devices to the Sb-based 3th generation imagers. [reprint (PDF)]
1.	Capacitance-voltage investigation of high purity InAs/GaSb superlattice photodiodes A. Hood, D. Hoffman, Y. Wei, F. Fuchs, and M. Razeghi Applied Physics Letters 88 (6)-- February 6, 2006 ...[Visit Journal] The residual carrier backgrounds of binary type-II InAs/GaSb superlattice photodiodes with cutoff wavelengths around 5 μm have been studied in the temperature range between 20 and 200 K. By applying a capacitance-voltage measurement technique, a residual background concentration below 10¹⁵ cm^–3 has been found. [reprint (PDF)]
1.	Influence of Residual Impurity Background on the Non-radiative Recombination Processes in High Purity InAs/GaSb superlattice Photodiodes E.C.F. da Silva, D. Hoffman, A. Hood, B. Nguyen, P.Y. Delaunay and M. Razeghi Applied Physics Letters, 89 (24)-- December 11, 2006 ...[Visit Journal] The influence of the impurity background on the recombination processes in type-II InAs/GaSb superlattice photodiodes with a cutoff wavelength of approximately 4.8 μm was investigated by electroluminescence measurements. Using an iterative fitting procedure based on the dependence of the quantum efficiency of the electroluminescence on the injection current, the Auger and Shockley-Read-Hall lifetimes were determined [reprint (PDF)]
1.	Surface Emitting, Tunable, Mid-Infrared Laser with High Output Power and Stable Output Beam Steven Slivken, Donghai Wu & Manijeh Razeghi Scientific Reports volume 9, Article number: 549-- January 24, 2019 ...[Visit Journal] A reflective outcoupler is demonstrated which can allow for stable surface emission from a quantum cascade laser and has potential for cost-effective wafer-scale manufacturing. This outcoupler is integrated with an amplified, electrically tunable laser architecture to demonstrate high power surface emission at a wavelength near 4.9 μm. Single mode peak power up to 6.7 W is demonstrated with >6 W available over a 90 cm⁻¹ (215 nm) spectral range. A high quality output beam is realized with a simple, single-layer, anti-reflective coating. The beam shape and profile are shown to be independent of wavelength. [reprint (PDF)]
1.	High power photonic crystal distributed feedback quantum cascade lasers emitting at 4.5 micron B. Gokden, S. Slivken and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7608, p. 760806-1-- January 22, 2010 ...[Visit Journal] Quantum cascade lasers possess very small linewidth enhancement factor, which makes them very prominent candidates for realization of high power, nearly diffraction limited and single mode photonic crystal distributed feedback broad area lasers in the mid-infrared frequencies. In this paper, we present room temperature operation of a two dimensional photonic crystal distributed feedback quantum cascade laser emitting at 4.5 µm. peak power up to ~0.9 W per facet is obtained from a 2 mm long laser with 100 µm cavity width at room temperature. The observed spectrum is single mode with a very narrow linewidth. Far-field profile has nearly diffraction limited single lobe with full width at half maximum of 3.5 degree normal to the facet. The mode selection and power output relationships are experimentally established with respect to different cavity lengths for photonic crystal distributed feedback quantum cascade lasers. [reprint (PDF)]
1.	High-power, room-temperature and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ = 4.8 µm J.S. Yu, S. Slivken, S.R. Darvish, A. Evans, B. Gokden and M. Razeghi Applied Physics Letters, 87 (4)-- July 25, 2005 ...[Visit Journal] The authors present high-power continuous-wave (cw) operation of distributed-feedback quantum-cascade lasers. Continuous-wave output powers of 56 mW at 25 °C and 15 mW at 40 °C are obtained. Single-mode emission near 7.8 µm with a side-mode suppression ratio of >=30 dB and a tuning range of 2.83 cm⁻¹ was obtained between 15 and 40 °C. The device exhibits no beam steering with a full width at half maximum of 27.4° at 25 °C in cw mode. [reprint (PDF)]
1.	High performance terahertz quantum cascade laser sources based on intracavity difference frequency generation Q.Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai and M. Razeghi Optics Express, Vol. 21, No. 1, p. 968-- January 14, 2013 ...[Visit Journal] We demonstrate high power, room temperature, single-mode THz emissions based on intracavity difference frequency generation from mid-infrared quantum cascade lasers. Dual active regions both featuring giant nonlinear susceptibilities are used to enhance the THz power and conversion efficiency. The THz frequency is lithographically tuned by integrated dual-period distributed feedback gratings with different grating periods. Single mode emissions from 3.3 to 4.6 THz with side-mode suppression ratio and output power up to 40 dB and 65 µW are obtained, with a narrow linewidth of 5 GHz. [reprint (PDF)]
1.	Electroluminescence of InAs/GaSb heterodiodes D. Hoffman, A. Hood, E. Michel, F. Fuchs, and M. Razeghi IEEE Journal of Quantum Electronics, 42 (2)-- February 1, 2006 ...[Visit Journal] The electroluminescence of a Type-II InAs-GaSb superlattice heterodiode has been studied as a function of injection current and temperature in the spectral range between 3 and 13 μm. The heterodiode comprises a Be-doped midwavelength infrared (MWIR) superlattice with an effective bandgap around 270 meV and an undoped long wavelength infrared (LWIR) superlattice with an effective bandgap of 115 meV. [reprint (PDF)]
1.	The importance of band alignment in VLWIR type-II InAs/GaSb heterodiodes containing the M-structure barrier D. Hoffman, B.M. Nguyen, E.K. Huang, P.Y. Delaunay, S. Bogdanov, P. Manukar, M. Razeghi, and V. Nathan SPIE Proceedings, San Jose, CA Volume 7222-15-- January 26, 2009 ...[Visit Journal] The Type-II InAs/GaSb superlattice photon detector is an attractive alternative to HgCdTe photodiodes and QWIPS. The use of p+ - pi - M - N+ heterodiode allows for greater flexibility in enhancing the device performance. The utilization of the Empirical Tight Binding method gives the band structure of the InAs/GaSb superlattice and the new M- structure (InAs/GaSb/AlSb/GaSb) superlattice allowing for the band alignment between the binary superlattice and the M- superlattice to be determined and see how it affects the optical performance. Then by modifying the doping level of the M- superlattice an optimal level can be determined to achieve high detectivity, by simultaneously improving both photo-response and reducing dark current for devices with cutoffs greater than 14.5 µm. [reprint (PDF)]
1.	High Frequency Extended Short-Wavelength Infrared Heterojunction Photodetectors Based on InAs/GaSb/AlSb Type-II Superlattices Romain Chevallier, Abbas Haddadi, Ryan McClintock, Arash Dehzangi , Victor Lopez-Dominguez, Pedram Khalili Amiri, Manijeh Razeghi IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 54, NO. 6-- December 1, 2018 ...[Visit Journal] InAs/GaSb/AlSb type-II superlattice-based photodetectors, with 50% cut-off wavelength of 2.1 µm and a −3 dB cut-off frequency of 4.8 GHz, are demonstrated, for 10 µm diameter circular mesas under 15 V applied reverse bias. A study of the cut-off frequency with applied bias and mesa size was performed to evaluate some of the limiting factors of photodetectors high frequency performance. [reprint (PDF)]
1.	High-Average-Power, High-Duty-Cycle (~6 μm) Quantum Cascade Lasers S. Slivken, A. Evans, J. David, and M. Razeghi Applied Physics Letters, 81 (23)-- December 2, 2002 ...[Visit Journal] High-power quantum cascade lasers emitting at λ = 6.1 μm are demonstrated. Accurate control of growth parameters and strain balancing results in a near-perfect lattice match, which leads to excellent material quality. Excellent peak power for uncoated lasers, up to 1.5 W per facet for a 21 μm emitter width, is obtained at 300 K for 30 period structures. The threshold current density at 300 K is only 2.4 kA/cm². From 300 to 425 K, the laser exhibits a characteristic temperature T₀ of 167 K. Next, Y₂O₃/Ti/Au mirror coatings were deposited on 1.5 mm cavities and mounted epilayer down. These lasers show an average output power of up to 225 mW at 17% duty cycle, and still show 8 mW average power at 45% duty cycle. [reprint (PDF)]
1.	AlGaN/AlN MOVPE heteroepitaxy: pulsed co-doping SiH4 and TMIn Ilkay Demir, Yusuf Koçak, A. Emre Kasapoğlu, Manijeh Razeghi, Emre Gür and Sezai Elagoz Semicond. Sci. Technol. 34 075028-- June 24, 2019 ...[Visit Journal] We report a new growth approach pulsed co-doping growth of Al_xGa_1−xN (x > 0.5) epilayers on AlN/Al₂O₃ templates by metal organic vapor phase epitaxy (MOVPE). Using this approach SiH₄ (silane) and TMIn (trimethylindium) supplied to the growth chamber alternately and pulsed during the growth of AlGaN epilayers. Structural and morphological quality of AlGaN epilayers were investigated by high resolution x-ray diffraction (HR-XRD), atomic force microscopy (AFM), Raman spectroscopy, and scanning electron microscopy (SEM) techniques. It has shown that higher crystalline quality with low full width at half maximum (FWHM) and smoother surface morphology with reduced hexagonal hillock density has been obtained by the pulsed co-doping growth approach. Volcano like hillock structures has been confirmed by Raman mapping. [reprint (PDF)]
1.	First Demonstration of ~ 10 microns FPAs in InAs/GaSb SLS M. Razeghi, P.Y. Delaunay, B.M. Nguyen, A. Hood, D. Hoffman, R. McClintock, Y. Wei, E. Michel, V. Nathan and M. Tidrow IEEE LEOS Newsletter 20 (5)-- October 1, 2006 ...[Visit Journal] The concept of Type-II InAs/GaSb superlattice was first brought by Nobel Laureate L. Esaki, et al. in the 1970s. There had been few studies on this material system until two decades later when reasonable quality material growth was made possible using molecular beam epitaxy. With the addition of cracker cells for the group V sources and optimizations of material growth conditions, the superlattice quality become significantly improved and the detectors made of these superlattice materials can meet the demand in some practical field applications. Especially in the LWIR regime, it provides a very promising alternative to HgCdTe for better material stability and uniformity, etc. We have developed the empirical tight binding model (ETBM) for precise determination of the superlattice bandgap. [reprint (PDF)]
1.	Widely tuned room temperature terahertz quantum cascade laser sources based on difference-frequency generation Q.Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai and M. Razeghi Applied Physics Letters, Vol. 101, No. 25, p. 251121-1-- December 17, 2012 ...[Visit Journal] We demonstrate room temperature THz quantum cascade laser sources with a broad spectral coverage based on intracavity difference-frequency generation. Two mid-infrared active cores based on the single-phonon resonance scheme are designed with a THz nonlinearity specially optimized at the high operating fields that correspond to the highest mid-infrared output powers. A Čerenkov phase-matching scheme along with integrated dual-period distributed feedback gratings are used for efficient THz extraction and spectral purification. Single mode emissions from 1.0 to 4.6 THz with a side-mode suppression ratio and output power up to 40 dB and 32 μW are obtained, respectively. [reprint (PDF)]
1.	Structural, Optical, Electrical and Morphological Study of Transparent p-NiO/n-ZnO Heterojunctions Grown by PLD V. E. Sandana, D. J. Rogers, F. Hosseini Teherani, P. Bove, N. Ben Sedrine, M. R. Correia, T. Monteiro, R. McClintock, and M. Razeghi Proc. SPIE 9364, Oxide-based Materials and Devices VI, 93641O-- March 24, 2015 ...[Visit Journal] NiO/ZnO heterostructures were fabricated on FTO/glass and bulk hydrothermal ZnO substrates by pulsed laser deposition. X-Ray diffraction and Room Temperature (RT) Raman studies were consistent with the formation of (0002) oriented wurtzite ZnO and (111) oriented fcc NiO. RT optical transmission studies revealed bandgap energy values of ~3.70 eV and ~3.30 eV for NiO and ZnO, respectively and more than 80% transmission for the whole ZnO/NiO/FTO/glass stack over the majority of the visible spectrum. Lateral p-n heterojunction mesas (~6mm x 6mm) were fabricated using a shadow mask during PLD growth. n-n and p-p measurements showed that Ti/Au contacting gave an Ohmic reponse for the NiO, ZnO and FTO. Both heterojunctions had rectifying I/V characteristics. The junction on FTO/glass gave forward bias currents (243mA at +10V) that were over 5 orders of magnitude higher than those for the junction formed on bulk ZnO. At ~ 10^-7 A (for 10V of reverse bias) the heterojunction leakage current was approximately two orders of magnitude lower on the bulk ZnO substrate than on FTO. Overall, the lateral p-NiO/n-ZnO/FTO/glass device proved far superior to that formed by growing p-NiO directly on the bulk n-ZnO substrate and gave a combination of electrical performance and visible wavelength transparency that could predispose it for use in various third generation transparent electronics applications. [reprint (PDF)]

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