Center for Quantum Devices - Most Downloaded Journal Articles

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23.	High Power, Room Temperature InP-Based Quantum Cascade Laser Grown on Si Steven Slivken and Manijeh Razeghi Journal of Quantum Electronics, Vol. 58, No. 6, 2300206 ...[Visit Journal] We report on the realization of an InP-based long wavelength quantum cascade laser grown on top of a silicon substrate. This demonstration first required the development of an epitaxial template with a smooth surface, which combines two methods of dislocation filtering. Once wafer growth was complete, a lateral injection buried heterostructure laser geometry was employed for efficient current injection and low loss. The laser emits at a wavelength of 10.8 μm and is capable of operation above 373 K, with a high peak power (>4 W) at room temperature. Laser threshold behavior with temperature is characterized by a T0 of 178 K. The far field beam shape is single lobed, showing fundamental transverse mode operation. [reprint (PDF)]
23.	Extended short-wavelength infrared nBn photodetectors based on type-II InAs/AlSb/GaSb superlattices with an AlAsSb/GaSb superlattice barrier A. Haddadi, R. Chevallier, A. Dehzangi, and M. Razeghi Applied Physics Letters 110, 101104-- March 8, 2017 ...[Visit Journal] Extended short-wavelength infrared nBn photodetectors based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate have been demonstrated. An AlAsSb/GaSb H-structure superlattice design was used as the large-bandgap electron-barrier in these photodetectors. The photodetector is designed to have a 100% cut-off wavelength of ∼2.8 μm at 300 K. The photodetector exhibited a room-temperature (300 K) peak responsivity of 0.65 A/W at 1.9 μm, corresponding to a quantum efficiency of 41% at zero bias under front-side illumination, without any anti-reflection coating. With an R × A of 78 Ω·cm² and a dark current density of 8 × 10⁻³ A/cm² under −400 mV applied bias at 300 K, the nBn photodetector exhibited a specific detectivity of 1.51 × 10¹⁰ Jones. At 150 K, the photodetector exhibited a dark current density of 9.5 × 10⁻⁹ A/cm² and a quantum efficiency of 50%, resulting in a detectivity of 1.12 × 10¹³ Jones. [reprint (PDF)]
23.	Anomalous Hall Effect in InSb Layers Grown by MOCVD on GaAs Substrates C. Besikci, Y.H. Choi, R. Sudharsanan, and M. Razeghi Journal of Applied Physics 73 (10)-- May 15, 1993 ...[Visit Journal] InSb epitaxial layers have been grown on GaAs substrates by low‐pressure metalorganic chemical vapor deposition. A 3.15 μm thick film yielded an x‐ray full width at half maximum of 171 arcsec. A Hall mobility of 76 200 cm²/V· s at 240 K and a full width at half maximum of 174 arcsec have been measured for a 4.85 μm thick epilayer. Measured Hall data have shown anomalous behavior. A decrease in Hall mobility with decreasing temperature has been observed and room‐temperature Hall mobility has increased with thickness. In order to explain the anomalous Hall data, and the thickness dependence of the measured parameters, the Hall coefficient and Hall mobility have been simulated using a three‐layer model including a surface layer, a bulklike layer, and an interface layer with a high density of defects. Theoretical analysis has shown that anomalous behavior can be attributed to donor-like defects caused by the large lattice mismatch and to a surface layer which dominates the transport in the material at low temperatures. [reprint (PDF)]
23.	Low Dark Current Deep UV AlGaN Photodetectors on AlN Substrate Lakshay Gautam, Junhee Lee, Gail Brown, Manijeh Razeghi IEEE Journal of Quantum Electronics, vol. 58, no. 3, pp. 1-5, June 2022, Art no. 4000205 ...[Visit Journal] We report high quality, low dark current, deep Ultraviolet AlGaN/AlN Photodetectors on AlN substrate. AlGaN based Photodetectors are grown and fabricated both on AlN and Sapphire substrates with the same epilayer structure. Subsequently, electrical characteristics of both photodetectors on AlN substrate and Sapphire are compared. A reduction of 4 orders of magnitude of dark current density is reported in UV detectors grown on AlN substrate with respect to Sapphire substrate. [reprint (PDF)]
23.	Band-gap narrowing and potential fluctuation in Si-doped GaN I.H. Lee, J.J. Lee, P. Kung, F.J. Sanchez, and M. Razeghi Applied Physics Letters 74 (1)-- January 4, 1999 ...[Visit Journal] We investigate the optical properties of two sets of Si-doped GaN epitaxial layers with different degree of compensation. The electron concentration dependence of the band-gap energy measured by photoluminescence is interpreted as band-gap narrowing effect and evaluated by a simple relation. The photoluminescence peak positions of heavily compensated samples are shifted downward with respect to those of moderately compensated samples, and the down shift becomes larger at higher electron density. Based on analysis of photoluminescence spectra, these prominent behaviors are accounted for by band-edge potential fluctuation associated with inhomogeneous residual impurities. [reprint (PDF)]
23.	Multi-color 4–20 μm In-P-based Quantum Well Infrared Photodetectors C. Jelen, S. Slivken, G.J. Brown, and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 ...[Visit Journal] In order to tune the wavelength of lattice-matched QWIP detectors over the range from 4 - 20 &mum, new designs are demonstrated for the first time which combine InGaAlAs and InGaAsP layers lattice-matched to InP and grown by gas-source molecular beam epitaxy. We demonstrate the first long-wavelength quantum well infrared photodetectors using the lattice-matched n-doped InGaAlAs/InP materials system. Samples with AlAs mole fractions of 0.0, 0.1, and 0.15 result in cutoff wavelengths of 8.5, 13.3, and 19.4 μm, respectively. A 45 degree facet coupled illumination responsivity of R equals 0.37 A/W and detectivity of D*(λ) equals 1x10⁹ cm·Hz^½·W^-1 at T = 77 K, for a cutoff wavelength λ_c equals 13.3 μm have been achieved. Based on the measured intersubband photoresponse wavelength, a null conduction band offset is expected for In_0.52Ga_0.21Al_0.27As/InP heterojunctions. We also report quantum well infrared photodetector structures of In_0.53Ga_0.47As/Al_0.48In_0.52As grown on InP substrate with photoresponse at 4 μm suitable for mid-wavelength infrared detectors. These detectors exhibit a constant peak responsivity of 30 mA/W independent of temperature in the range from T equals 77 K to T equals 200 K. Combining these two materials, we report the first multispectral detectors that combine lattice-matched quantum wells of InGaAs/InAlAs and InGaAs/InP. Utilizing two contacts, a voltage tunable detector with (lambda) p equals 8 micrometer at a bias of V equals 5 V and λ_p equals 4 μm at V equals 10 V is demonstrated. [reprint (PDF)]
23.	Mid‑wavelength infrared avalanche photodetector with AlAsSb/GaSb superlattice Jiakai Li, Arash Dehzangi, Gail Brown, Manijeh Razeghi Scientifc Reports \| (2021) 11:7104 \| https://doi.org/10.1038/s41598-021-86566-8 ...[Visit Journal] In this work, a mid-wavelength infrared separate absorption and multiplication avalanche photodiode (SAM-APD) with 100% cut-of wavelength of ~ 5.0 µm at 200 K grown by molecular beam epitaxy was demonstrated. The InAsSb-based SAM-APD device was designed to have electron dominated avalanche mechanism via the band structure engineered multi-quantum well structure based on AlAsSb/GaSb H-structure superlattice and InAsSb material in the multiplication region. The device exhibits a maximum multiplication gain of 29 at 200 K under -14.7 bias voltage. The maximum multiplication gain value for the MWIR SAM-APD increases from 29 at 200 K to 121 at 150 K. The electron and hole impact ionization coefficients were derived and the large difference between their value was observed. The carrier ionization ratio for the MWIR SAM-APD device was calculated to be ~ 0.097 at 200 K. [reprint (PDF)]
23.	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)]
23.	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)]
23.	Modeling Type-II InAs/GaSb Superlattices Using Empirical Tight-Binding Method: New Aspects Y. Wei, M. Razeghi, G.J. Brown, and M.Z. Tidrow SPIE Conference, Jose, CA, Vol. 5359, pp. 301-- January 25, 2004 ...[Visit Journal] The recent advances in the experimental work on the Type-II InAs/GaSb superlattices necessitate a modeling that can handle arbitrary layer thickness as well as different types of interfaces in order to guide the superlattice design. The empirical tight-binding method (ETBM) is a very good candidate since it builds up the Hamiltonian atom by atom. There has been a lot of research work on the modeling of Type-II InAs/GaSb superlattices using the ETBM. However, different groups generate very different accuracy comparing with experimental results. We have recently identified two major aspects in the modeling: the antimony segregation and the interface effects. These two aspects turned out to be of crucial importance governing the superlattice properties, especially the bandgap. We build the superlattice Hamiltonian using antimony segregated atomic profile taking into account the interface. Our calculations agree with our experimental results within growth uncertainties. In addition we introduced the concept of Ga_xIn_1-x type interface engineering, which will add another design freedom especially in the mid-wavelength infrared range (3~7 µm) in orderto reduce the lattice mismatch. [reprint (PDF)]
23.	Novel Sb-based Alloys for Uncooled Infrared Photodetector Applications M. Razeghi SPIE Conference, San Jose, CA, -- January 22, 2001 ...[Visit Journal] We report on the growth and characterization of InSbBi, InTlSb, InTlP, and the quaternary alloys for uncooled long- wavelength infrared photodetector applications. The layers were grown on InSb and GaAs substrates by low-pressure metalorganic chemical vapor deposition. The incorporation of Bi and Tl in InSb was investigated with high-resolution x-ray diffraction, energy dispersive x-ray analysis, and optical photoresponse measurements. We also demonstrate the photodetectors fabricated from the grown InSbBi and InTlSb alloys. InSb_0.96Bi_0.04 photoconductive detectors exhibited a responsivity of 3.2 V/W at 77 K. The estimated Johnson noise limited detectivityat 7 micrometers was 1.7 X 10⁸ cm·Hz^½/W at 77 K. A room temperature operating InSb_0.95Bi_0.05 photodetector was also demonstrated.Photoresponse up to 12 micrometers was achieved at 300 K. The responsivity and Johnson noise-limited detectivity at 10.6 μm were 1.9 mV/W and 1.2 X 10⁶ cm·Hz^½/W, respectively. Photoresponse up to 15 μm was achieved at 300 K from quaternary InTlAsSb and InBiAsSb alloys. [reprint (PDF)]
23.	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)]
23.	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)]
23.	Low-threshold and high power (~9.0 μm) quantum cascade lasers operating at room temperature A. Matlis, S. Slivken, A. Tahraoui, K.J. Luo, J. Diaz, Z. Wu, A. Rybaltowski, C. Jelen, and M. Razeghi Applied Physics Letters 77 (12)-- September 18, 2000 ...[Visit Journal] We report a low threshold current density and high power for λ ∼ 9 μm AlInAs/GaInAs quantum cascade lasers operating at room temperature. The threshold current density is 1.95 kA/cm² at 300 K and 0.61 kA/cm² at 80 K for 5 μs pulses at 200 Hz repetition rate. The peak output power is 700 mW at room temperature and 1.3 W at 80 K per two facets for cavity length is 3 mm with a stripe width of 20 μm. The characteristic temperature T₀ is 185 °C. The slope efficiency is 450 and 800 mW/A at 300 and 80 K, respectively. In continuous wave operation, the output power is more than 150 mW at 80 K and 25 mW at 140 K. This high performance was achieved by improving the material growth and processing technology. [reprint (PDF)]
23.	High power, continuous wave, room temperature operation of λ ~ 3.4 μm and λ ~ 3.55 μm InP-based quantum cascade lasers N. Bandyopadhyay, S. Slivken, Y. Bai and M. Razeghi Applied Physics Letters, Vol. 100, No. 21, p. 212104-1-- May 21, 2012 ...[Visit Journal] We report two highly strain-balanced InP-based AlInAs/GaInAs quantum cascade lasers emitting near 3.39 and 3.56 . A pulsed threshold current density of only 1.1 kA/cm² has been achieved at room temperature for both lasers with characteristic temperatures (T₀) of 166 K and 152 K, respectively. The slope efficiency is also relatively temperature insensitive with characteristic temperatures (T₁) of 116 K and 191 K, respectively. Continuous wave powers of 504 mW and 576 mW are obtained at room temperature, respectively. This was accomplished without buried ridge processing. [reprint (PDF)]
23.	Demonstration of long wavelength infrared Type-II InAs/InAs_1-xSb_x superlattices photodiodes on GaSb substrate grown by metalorganic chemical vapor deposition D. H. Wu, A. Dehzangi, Y. Y. Zhang, M. Razeghi Applied Physics Letters 112, 241103-- June 12, 2018 ...[Visit Journal] We report the growth and characterization of long wavelength infrared type-II InAs/InAs_1−xSb_x superlattices photodiodes with a 50% cut-off wavelength at 8.0 μm on GaSb substrate grown by metalorganic chemical vapor deposition. At 77 K, the photodiodes exhibited a differential resistance at zero bias (R₀A) 8.0 Ω·cm², peak responsivity of 1.26 A/W corresponding to a quantum efficiency of 21%. A specific detectivity of 5.4×10¹⁰ cm·Hz^1/2/W was achieved at 7.5 μm. [reprint (PDF)]
23.	Solar-blind avalanche photodiodes R. McClintock, K. Minder, A. Yasan, C. Bayram, F. Fuchs, P. Kung and M. Razeghi SPIE Conference, San Jose, CA, Vol. 6127, pp. 61271D-- January 23, 2006 ...[Visit Journal] There is a need for semiconductor based UV photodetectors to support avalanche gain in order to realize better performance and more effectively compete with existing photomultiplier tubes. However, there are numerous technical issues associated with the realization of high-quality solar-blind avalanche photodiodes (APDs). In this paper, APDs operating at 280 nm, within the solar-blind region of the ultraviolet spectrum, are investigated. [reprint (PDF)]
23.	Room temperature terahertz semiconductor frequency comb Quanyong Lu, Feihu Wang, Donghai Wu, Steven Slivken & Manijeh Razeghi Nature Communications 10, 2403-- June 3, 2019 ...[Visit Journal] A terahertz (THz) frequency comb capable of high-resolution measurement will significantly advance THz technology application in spectroscopy, metrology and sensing. The recently developed cryogenic-cooled THz quantum cascade laser (QCL) comb has exhibited great potentials with high power and broadband spectrum. Here, we report a room temperature THz harmonic frequency comb in 2.2 to 3.3 THz based on difference-frequency generation from a mid-IR QCL. The THz comb is intracavity generated via down-converting a mid-IR comb with an integrated mid-IR single mode based on distributed-feedback grating without using external optical elements. The grating Bragg wavelength is largely detuned from the gain peak to suppress the grating dispersion and support the comb operation in the high gain spectral range. Multiheterodyne spectroscopy with multiple equally spaced lines by beating it with a reference Fabry-Pérot comb confirms the THz comb operation. This type of THz comb will find applications to room temperature chip-based THz spectroscopy. [reprint (PDF)]
23.	Extremely high electron mobility in a GaAs‐GaxIn1−xP heterostructure grown by metalorganic chemical vapor deposition M. Razeghi; M. Defour; F. Omnes; M. Dobers; J. P. Vieren; Y. Guldner Appl. Phys. Lett. 55, 457–459 (1989)-- June 17, 1989 ...[Visit Journal] On studying the magnetoresistivity of GaAs-GalnP heterostructures grown by low-pressure metalorganic chemical vapor deposition in magnetic fields up to 12 T and at liquid-helium temperatures, we have observed extremely high electron mobilities. Using the persistent photoconductivity effect, by illumination with red light, we reached a mobility of 780 000 cm2 / (V s) at an electron density of 4.1 X lOll cm- 2 . This high electron mobility is confirmed by cyclotron resonance measurements< [reprint (PDF)]
23.	Gas Source Molecular Beam Epitaxy Growth and Characterization of Ga_0.51In_0.49P/In_xGa_1-xAs/GaAs Modulation-doped Field-effect Transistor Structures C. Besikci, Y. Civan, S. Ozder, O. Sen, C. Jelen, S. Slivken, and M. Razeghi Semiconductor Science Technology 12-- January 1, 1997 ...[Visit Journal] Lattice-matched Ga_0.51In_0.49P/GaAs and strained Ga_0.51In_0.49P/In_xGa_1−xAs/GaAs (0.1 ≤ x ≤ 0.25) modulation-doped field-effect transistor structures were grown by gas source molecular beam epitaxy by using Si as dopant. Detailed electrical characterization results are presented. The Ga_0.5In_0.49P/In_0.25Ga_0.75As/GaAs sample yielded dark two-dimensional electron gas densities of 3.75 x 10¹² cm^-2 (300 K) and 2.3 x 10¹² cm^-2 (77 K) which are comparable to the highest sheet electron densities reported in AlGaAs/InGaAs/GaAs and InAlAs/InGaAs/InP modulation-doped heterostructures. Persistent photoconductivity was observed in the strained samples only. A 0.797 eV deep level has been detected in the undoped GaInP layers of the structures. Another level, with DLTS peak height dependent on the filling pulse width, has been detected at the interface of the strained samples. Based on the DLTS and Hall effect measurement results, this level, which seems to be the origin of persistent photoconductivity, can be attributed to the strain relaxation related defects. [reprint (PDF)]
23.	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)]
23.	Unleashing light: a deep dive into quantum cascade laser dynamics through power, precision, and performance Xiaohan Yu, Yanbo Bai, Feihu Wang, Steve Slivken, Nirajman Shrestha, Ruiming Zhang, Nil Ozcevik, Manijeh Razeghi Proc. SPIE 13908, Quantum Sensing and Nano Electronics and Photonics XXII, 139080U (20 March 2026); https://doi.org/10.1117/12.3082051 ...[Visit Journal] In this study, we explore the complex interplay of structural design and performance metrics in InGaAs/InAlAs/InP ridge waveguide quantum cascade lasers (QCLs) by combining theoretical modeling with rigorous experimental validation. By assuming mirror loss corresponding to a facet reflectivity of R = 0.275, which represents the Fresnel reflectance of uncoated InP facets, we investigated the impact of cavity length on threshold current density and slope efficiency by analyzing Power–Current–Voltage (PIV) characteristics of uncoated QCLs with lengths of 3mm, 4mm, and 5mm. Slope efficiencies were extracted and corrected for single-facet detection. By leveraging fitting techniques across multiple datasets and laser structure, we quantified internal and external quantum efficiencies and determined the transparency current density using graphical and analytical methods. A linear regression of inverse external efficiency versus inverse mirror loss enabled estimation of the internal quantum efficiency, highlighting the direct influence of fabrication parameters on laser output. With a linear fit of threshold current density versus mirror loss, the transparency current density was calculated. This work not only reinforces foundational laser physics principles but also provides a hands-on methodology for analyzing active device parameters with practical implications in tunable mid-infrared sources, spectroscopy, and optical sensing. [reprint (PDF)]
23.	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)]
23.	Widely tunable room temperature semiconductor terahertz source Q. Y. Lu, S. Slivken, N. Bandyopadhyay, Y. Bai, and M. Razeghi Appl. Phys. Lett. 105, 201102-- November 17, 2014 ...[Visit Journal] We present a widely tunable, monolithic terahertz source based on intracavity difference frequency generation within a mid-infrared quantum cascade laser at room temperature. A three-section ridge waveguide laser design with two sampled grating sections and a distributed-Bragg section is used to achieve the terahertz (THz) frequency tuning. Room temperature single mode THz emission with a wide tunable frequency range of 2.6–4.2 THz (∼47% of the central frequency) and THz power up to 0.1 mW is demonstrated, making such device an ideal candidate for THz spectroscopy and sensing. [reprint (PDF)]
23.	High performance InGaAs/InGaP quantum dot infrared photodetector achieved through doping level optimization S. Tsao, K. Mi, J. Szafraniec, W. Zhang, H. Lim, B. Movaghar, and M. Razeghi SPIE Conference, Jose, CA, Vol. 5732, pp. 334-- January 22, 2005 ...[Visit Journal] We report an InGaAs/InGaP/GaAs quantum dot infrared photodetector grown by metalorganic chemical vapor deposition with detectivity of 1.3x10¹¹ cm·Hz^½/W at 77K and 1.2x10¹⁰ ccm·Hz^½/W at 120K. Modeling of the Quantum dot energy levels showed us that increased photoresponse could be obtained by doping the quantum dots to 4 electrons per dot instead of the usual 2 electrons per dot. This happens because the primary photocurrent transition is from the first excited state to a higher excited state. Increasing the quantum doping in our device yielded significant responsivity improvement and much higher detectivity as a result. This paper discusses the performance of this higher doping device and compares it to our previously reported device with lower doping. [reprint (PDF)]

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