Center for Quantum Devices - Most Downloaded Journal Articles

Page 17 of 31: Prev << 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 >> Next (768 Items)

17.	ZnO Thin Films & Nanostructures for Emerging Optoelectronic Applications D.J. Rogers, F. Hosseini Teherani, V.E. Sandana, and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7605, p. 76050K-1-- January 27, 2010 ...[Visit Journal] ZnO-based thin films and nanostructures grown by PLD for various emerging optoelectronic applications. AZO thin films are currently displacing ITO for many TCO applications due to recent improvements in attainable AZO conductivity combined with processing, cost and toxicity advantages. Advances in the channel mobilities and Id on/off ratios in ZnO-based TTFTs have opened up the potential for use as a replacement for a-Si in AM-OLED and AM-LCD screens. Angular-dependent specular reflection measurements of self-forming, moth-eye-like, nanostructure arrays grown by PLD were seen to have <0.5% reflectivity over the whole visible spectrum for angles of incidence between 10 and 60 degrees. Such nanostructures may be useful for applications such as AR coatings on solar cells. Compliant ZnO layers on mismatched/amorphous substrates were shown to have potential for MOVPE regrowth of GaN. This approach could be used as a means to facilitate lift-off of GaN-based LEDs from insulating sapphire substrates and could allow the growth of InGaN-based solar cells on cheap substrates. The green gap in InGaN-based LEDs was combated by substituting low Ts PLD n-ZnO for MOCVD n-GaN in inverted hybrid heterojunctions. This approach maintained the integrity of the InGaN MQWs and gave LEDs with green emission at just over 510 nm. Hybrid n-ZnO/p-GaN heterojunctions were also seen to have the potential for UV (375 nm) EL, characteristic of ZnO NBE emission. This suggests that there was significant hole injection into the ZnO and that such LEDs could profit from the relatively high exciton binding energy of ZnO. [reprint (PDF)]
17.	Comparison of Gain and Threshold Current Density for InGaAsP/GaAs λ = 808 nm) Lasers with Different Quantum-Well Thickness H.J. Yi, J. Diaz, I. Eliashevich, G. Lukas, S. Kim, D. Wu, M. Erdtmann, C. Jelen, S. Slivken, L.J. Wang, and M. Razeghi Journal of Applied Physics 79 (11)-- July 1, 1996 ...[Visit Journal] We investigated the quantum‐size effects of quantum well (QW) on gain and threshold current density for InGaAsP/GaAs (λ=808 nm) laser diodes. In this work, a comparison is made of lasers with different QW thickness while keeping the optical confinement factors constant. We found that the threshold current density and differential efficiency were not affected by narrowing the QW thickness. The theoretical model taking into account the mixing of the valence bands and momentum relaxation for InGaAsP/GaAs lasers with spontaneous emission (optically pumped) measurement shows that the absence of difference between these structures can be attributed to the high relaxation rate. [reprint (PDF)]
17.	AlGaN ultraviolet detectors M. Razeghi and A. Rogalski, SPIE Conference, San Jose, CA, -- February 12, 1997 ...[Visit Journal] Hitherto, the semiconductor ultraviolet (UV) detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main efforts are currently directed to anew generation of UV detectors fabricated from wide-band-gap semiconductors between them the most promising are diamond and AlGaN. The latest progress in development of AlGaN UV detectors is described in detail. [reprint (PDF)]
17.	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)]
17.	High Quality Aluminum Nitride Epitaxial Layers Grown on Sapphire Substrates A. Saxler, P. Kung, C.J. Sun, E. Bigan and M. Razeghi Applied Physics Letters 64 (3)-- January 17, 1994 ...[Visit Journal] In this letter we report the growth of high quality AlN epitaxial layers on sapphire substrates. The AlN grown on (00·1) sapphire exhibited a better crystalline quality than that grown on (01·2) sapphire. An x-ray rocking curve of AlN on (00·1) Al₂O₃ yielded a full width at half-maximum of 97.2 arcsec, which is the narrowest value reported to our knowledge. The AlN peak on (01·2) Al₂O₃ was about 30 times wider. The absorption edge measured by ultraviolet transmission spectroscopy for AlN grown on (00·1) Al₂O₃ was about 197 nm. [reprint (PDF)]
17.	Core-shell GaN-ZnO Moth-eye Nanostructure Arrays Grown on a-SiO₂/Si (111) as a basis for Improved InGaN-based Photovoltaics and LEDs D.J. Rogers, V.E. Sandana, S. Gautier, T. Moudakir, M. Abid, A. Ougazzaden, F. Hosseini Teherani, P. Bove, M. Molinari, M. Troyon, M. Peres, Manuel J. Soares, A.J. Neves, T. Monteiro, D. McGrouther, J.N. Chapman, H.-J. Drouhin, R. McClintock, M. Razeghi Photonics and Nanostructures - Fundamentals and Applications, Volume 15, Pages 53-58-- March 30, 2015 ...[Visit Journal] Self-forming, vertically-aligned, ZnO moth-eye-like nanoarrays were grown by catalyst-free pulsed laser deposition on a-SiO₂/Si (111) substrates. X-Ray Diffraction (XRD) and Cathodoluminescence (CL) studies indicated that nanostructures were highly c-axis oriented wurtzite ZnO with strong near band edge emission. The nanostructures were used as templates for the growth of non-polar GaN by metal organic vapor phase epitaxy. XRD, scanning electron microscopy, energy dispersive X-ray microanalysis and CL revealed ZnO encapsulated with GaN, without evidence of ZnO back-etching. XRD showed compressive epitaxial strain in the GaN, which is conducive to stabilization of the higher indium contents required for more efficient green light emitting diode (LED) and photovoltaic (PV) operation. Angular-dependent specular reflection measurements showed a relative reflectance of less than 1% over the wavelength range of 400–720 nm at all angles up to 60°. The superior black-body performance of this moth-eye-like structure would boost LED light extraction and PV anti-reflection performance compared with existing planar or nanowire LED and PV morphologies. The enhancement in core conductivity, provided by the ZnO, would also improve current distribution and increase the effective junction area compared with nanowire devices based solely on GaN. [reprint (PDF)]
17.	Minority electron unipolar photodetectors based on Type-II InAs/GaSb/AlSb superlattices for very long wavelength infrared detection B.M. Nguyen, S. Abdollahi Pour, S. Bogdanov and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7608, p. 760825-1-- January 22, 2010 ...[Visit Journal] The bandstructure tunability of Type-II antimonide-based superlattices has been significantly enhanced since the introduction of the M-structure superlattice, resulting in significant improvements of Type-II superlattice infrared detectors. By using M-structure, we developed the pMp design, a novel infrared photodetector architecture that inherits the advantages of traditional photoconductive and photovoltaic devices. This minority electron unipolar device consists of an M-structure barrier layer blocking the transport of majority holes in a p-type semiconductor, resulting in an electrical transport due to minority carriers with low current density. Applied for the very long wavelength detection, at 77K, a 14µm cutoff detector exhibits a dark current 3.3 mA·cm⁻², a photoresponsivity of 1.4 A/W at 50mV bias and the associated shot-noise detectivity of 4x10¹⁰ Jones. [reprint (PDF)]
17.	Very high quantum efficiency in type-II InAs/GaSb superlattice photodiode with cutoff of 12 µm B.M. Nguyen, D. Hoffman, Y. Wei, P.Y. Delaunay, A. Hood and M. Razeghi Applied Physics Letters, Vol. 90, No. 23, p. 231108-1-- June 4, 2007 ...[Visit Journal] The authors report the dependence of the quantum efficiency on device thickness of Type-II InAs/GaSb superlattice photodetectors with a cutoff wavelength around 12 µm. The quantum efficiency and responsivity show a clear delineation in comparison to the device thickness. An external single-pass quantum efficiency of 54% is obtained for a 12 µm cutoff wavelength photodiodes with a -region thickness of 6.0 µm. The R₀A value is kept stable for the range of structure thicknesses allowing for a specific detectivity (2.2×10¹¹ cm·Hz^½/W). [reprint (PDF)]
17.	Quantum Dot Infrared Photodetectors: Comparison Experiment and Theory H. Lim, W. Zhang, S. Tsao, T. Sills, J. Szafraniec, K. Mi, B. Movaghar, and M. Razeghi Physical Review B, 72-- August 17, 2005 ...[Visit Journal] We present data and calculations and examine the factors that determine the detectivities in self-assembled InAs and InGaAs based quantum dot infrared photodetectors (QDIPs). We investigate a class of devices that combine good wavelength selectivity with “high detectivity.” We study the factors that limit the temperature performance of quantum dot detectors. For this we develop a formalism to evaluate the optical absorption and the electron transport properties. We examine the performance limiting factors and compare theory with experimental data. We find that the notion of a phonon bottleneck does not apply to large-diameter lenslike quantum dots, which have many closely spaced energy levels. The observed strong decrease of responsivity with temperature is ultimately due to a rapid thermal cascade back into the ground states. High temperature performance is improved by engineering the excited state to be near the continuum. The good low temperature (77 K) performance in strongly bound QDIPs is shown to be due to the high gain and the low noise achievable in these micron size devices. [reprint (PDF)]
17.	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)]
17.	Room temperature terahertz quantum cascade laser sources with 215 μW output power through epilayer-down mounting Q. Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai, and M. Razeghi Appl. Phys. Lett. 103, 011101 (2013)-- July 1, 2013 ...[Visit Journal] We report room temperature terahertz (THz) quantum cascade laser sources with high power based on difference frequency generation. The device is Čerenkov phase matched and spectrally purified with an integrated dual-period distributed-feedback grating. Symmetric current injection and epilayer-down mounting of the device onto a patterned submount are used to improve the electrical uniformity and heat removal, respectively. The epilayer-down mounting also allows for THz anti-reflective coating to enhance the THz outcoupling efficiency. Single mode emission at 3.5 THz with a side-mode suppression ratio and output power up to 30 dB and 215 μW are obtained, respectively. [reprint (PDF)]
17.	Engineering Multi-Section Quantum Cascade Lasers for Broadband Tuning Steven Slivken and Manijeh Razeghi Photonics 3, 41-- June 27, 2016 ...[Visit Journal] In an effort to overcome current limitations to electrical tuning of quantum cascade lasers, a strategy is proposed which combines heterogeneous quantum cascade laser gain engineering with sampled grating architectures. This approach seeks to not only widen the accessible spectral range for an individual emitter, but also compensate for functional non-uniformity of reflectivity and gain lineshapes. A trial laser with a dual wavelength core is presented which exhibits electroluminescence over a 750 cm⁻¹ range and discrete single mode laser emission over a 700 cm⁻¹ range. Electrical tuning over 180 cm⁻¹ is demonstrated with a simple sampled grating design. A path forward to even wider tuning is also described using more sophisticated gain and grating design principles. [reprint (PDF)]
17.	Low frequency noise in 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 SPIE Proceedings, Vol. 8268, p. 82680X-- January 22, 2012 ...[Visit Journal] Recently, the type-II InAs/GaSb superlattice (T2SL) material platform is considered as a potential alternative for HgCdTe technology in long wavelength infrared (LWIR) imaging. This is due to the incredible growth in the understanding of its material properties and improvement of device processing which leads to design and fabrication of better devices. In this paper, we report electrical low frequency noise measurement on a high performance type-II InAs/GaSb superlattice 1024×1024 LWIR focal plane array. [reprint (PDF)]
17.	2.4 W room temperature continuous wave operation of distributed feedback quantum cascade lasers Q.Y. Lu, Y. Bai, N. Bandyopadhyay, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 98, No. 18, p. 181106-1-- May 4, 2011 ...[Visit Journal] We demonstrate high power continuous-wave room-temperature operation surface-grating distributed feedback quantum cascade lasers at 4.8 μm. High power single mode operation benefits from a combination of high-reflection and antireflection coatings. Maximum single-facet continuous-wave output power of 2.4 W and peak wall plug efficiency of 10% from one facet is obtained at 298 K. Single mode operation with a side mode suppression ratio of 30 dB and single-lobed far field without beam steering is observed. [reprint (PDF)]
17.	High quantum efficiency two color type-II InAs/GaSb n-i-p-p-i-n photodiodes P.Y. Delaunay, B.M. Nguyen, D. Hoffman, A. Hood, E.K. Huang, M. Razeghi, and M.Z. Tidrow Applied Physics Letters, Vol. 92, No. 11, p. 111112-1-- March 17, 2008 ...[Visit Journal] A n-i-p-p-i-n photodiode based on type-II InAs/GaSb superlattice was grown on a GaSb substrate. The two channels, with respective 50% of responsivity cutoff wavelengths at 7.7 and 10 µm, presented quantum efficiencies (QEs) of 47% and 39% at 77 K. The devices can be operated as two diodes for simultaneous detection or as a single n-i-p-p-i-n detector for sequential detection. In the latter configuration, the QEs at 5.3 and 8.5 µm were measured as high as 40% and 39% at 77 K. The optical cross-talk between the two channels could be reduced from 0.36 to 0.08 by applying a 50 mV bias. [reprint (PDF)]
17.	Background Limited Performance in p-doped GaAs/Ga[0.71]In[0.29]As[0.39]P[0.61] Quantum Well Infrared Photodetectors J. Hoff, S. Kim, M. Erdtmann, R. Williams, J. Piotrowski, E. Bigan, M. Razeghi and G. Brown Applied Physics Letters 67 (1)-- July 3, 1995 ...[Visit Journal] Background limited infrared photodetection has been achieved up to 100 K at normal incidence with p-type GaAs/Ga_0.71In_0.29As_0.39P_0.61 quantum well intersubband photodetectors grown by low-pressure metalorganic chemical vapor deposition. Photoresponse covers the wavelength range from 2.5 μm up to 7 μm. The device shows photovoltaic response, the cutoff wavelength increases slightly with bias, and the responsivity increases nonlinearly with bias. These effects are attributed to an asymmetric quantum well profile. [reprint (PDF)]
17.	Improved performance of IR photodetectors with 3D gap engineering J. Piotrowski and M. Razeghi Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995 ...[Visit Journal] The ultimate signal-to-noise performance of the semiconductor photodetector is limited by the statistical fluctuations of the thermal generation and recombination rates in photodetector material. Cooling is an effective but impractical way of suppression of the thermal processes. The performance of uncooled detectors can be improved by minimizing the thermal generation and recombination rates and reducing the actual volume of photodetector. This can be realized in 3D heterostructure devices. In these devices, the incident radiation is absorbed in small regions of narrow gap semiconductor, buried in wide gap volume and supplied with wide gap electric contacts and radiation concentrators. The practical near room-temperature 1 - 12 μm IR heterostructure photodetectors are reported. The devices are based on variable gap Hg_1-xCd_xTe. The 3D heterostructures have been obtained by Isothermal Vapor Growth Epitaxy in a reusable growth system which enables in situ doping during growth with foreign impurities. Ion milling was extensively used in preparation of the devices. Monolithic optical immersion has been applied for further improvement of performance. The 3D heterostructure devices exhibit performance exceeding that of conventional photodetectors. [reprint (PDF)]
17.	GaInAs and GaInAsP materials grown by low pressure MOCVD for microwave and optoelectronic applications J.P. Duchemin, J.P. Hirtz, M. Razeghi, M. Bonnet , S.D. Hersee J.P. Duchemin, J.P. Hirtz, M. Razeghi, M. Bonnet, S.D. Hersee, GaInAs and GaInAsP materials grown by low pressure MOCVD for microwave and optoelectronic applications, Journal of Crystal Growth, Volume 55, Issue 1, 1981, Pages 64-73-- October 1, 1981 ...[Visit Journal] The low pressure MOCVD technique has been successfully used to grow GaInAsP, lattice-matched to InP, for the complete compositional range between InP (λ=0.91 μm) and the ternary compound Ga0.47In0.53As (λ=1.67 μm). By contrast to LPE growth it has been found that during the MOCVD growth of double heterostructures InP can be grown directly onto the ternary or quaternary with no disturbance of the active layer, i.e. there is no effect equivalent to “melt back”. The compositional grading on both sides of the active layer was measured by scanning Auger spectroscopy on bevelled samples. It was found that the graded regions were typically less than 100 Å wide for GaInAsP active layers and less than 50 Å wide for GaInAs active layers. Single layers of undoped GaInAs exhibited a typical mobility of 6700 cm2 V-1s-1 at 1.5×1017 cm-3. The compositional uniformity of the ternary layers was characterised by measurement of the photoluminescence wavelength at various points on a large sample. The wavelength varied by <3 nm over 95% of the area, which was approximately 8 cm2. Our early MOCVD grown GaInAsP/InP DH lasers exhibited high thresholds due to a poor interface between the p-InP and the active layer. However, recently fabricated broad area lasers emitting at 1.27 μm show an average threshold current density of 1.5 kA cm-2 with a T0 of between 70 to 80 K. Stripe geometry lasers have being fabricated from this material and CW operation has been obtained. [reprint (PDF)]
17.	Fabrication of nanostructured heterojunction LEDs using self-forming Moth-Eye Arrays of n-ZnO Nanocones Grown on p-Si (111) by PLD D.J. Rogers; V.E. Sandana; F. Hosseini Teherani; M. Razeghi; H.-J. Drouhin Proc. SPIE 7217, Zinc Oxide Materials and Devices IV, 721708 (February 17, 2009)-- February 17, 2009 ...[Visit Journal] ZnO nanostructures were grown on Si (111) substrates using Pulsed Laser Deposition. The impact of growth temperature (T_s) and Ar pressure (P_Ar) on the morphology, crystal structure and photoluminescence was investigated. Various types of ZnO nanostructures were obtained. Self-forming arrays of vertically-aligned nanorods and nanocones with strong c-axis crystallographic orientation and good optical response were obtained at higher T_s. The nanocone, or "moth-eye" type structures were selected for LED development because of their graded effective refractive index, which could facilitate improved light extraction at the LED/air interface. Such moth-eye arrays were grown on p-type Si (111) substrates to form heteroj unction LEDs with the n-type ZnO nanocones acting as an active component of the device. These nanostructured LEDs gave rectifying I/V characteristics with a threshold voltage of about 6V and a blueish-white electroluminescence, which was clearly visible to the naked eye. [reprint (PDF)]
17.	High Performance Planar Antimony-Based Superlattice Photodetectors Using Zinc Diffusion Grown by MBE Jiakai Li, R. K. Saroj, Steven Slivken, V. H. Nguyen, Gail Brown and Manijeh Razeghi Photonics 2022, 9, 664 ...[Visit Journal] In this letter, we report a mid-wavelength infrared (MWIR) planar photodetector based on InAs/InAsSb type-II superlattices (T2SLs) that has a cut-off wavelength of 4.3 um at 77 K. The superlattice for the device was grown by molecular beam epitaxy while the planar device structure was achieved by Zinc diffusion process in a metal–organic chemical vapor deposition reactor. At 77 K, the peak responsivity and the corresponding quantum efficiency had the value of 1.42 A/W and 48% respectively at 3.7 um under -20 mV for the MWIR planar photodetector. At 77 K, the MWIR planar photodetector exhibits a dark current density of 2.0E5 A/cm^2 and the R0A value of ~3.0E2 Ohm cm^2 under -20 mV, which yielded a specific detectivity of 4.0E11 cm Hz^(1/2)/W at 3.7 um. At 150 K, the planar device showed a dark current density of 6.4E-5 A/cm^2 and a quantum efficiency of 49% at ~3.7 um under -20 mV, which yielded a specific detectivity of 2.0E11 cm Hz^(1/2)/W. [reprint (PDF)]
17.	The Molecular Beam Epitaxial Growth of InSb on (111) GaAs E. Michel, J. Kim, J. Xu, S. Javadpour, I. Ferguson, and M. Razeghi Applied Physics Letters 69 (2)-- July 8, 1996 ...[Visit Journal] The molecular beam epitaxial growth of InSb on (111)B GaAs has been investigated. It was found that for a given Sb/In ratio, a higher growth temperature was required for the growth of InSb on (111)B GaAs compared to that on (001) GaAs. This difference has been attributed to the bonding characteristics of the (111)B and (001) surface. Once growth had been optimized, it was found that the material characteristics of (111)B InSb were almost identical to that of (001) InSb, i.e., independent of orientation. For example, the x-ray full width at half-maximum and 300 K mobility had the same absolute values for (111) InSb and (001)InSb and followed the same dependence with the sample thickness. Te was found to be a well-behaved n-type dopant for (111)B InSb. [reprint (PDF)]
17.	p-doped GaAs/Ga_0.51In_0.49P quantum well intersub-band photodetectors J. Hoff, X. He, M. Erdtmann, E. Bigan, M. Razeghi, and G.J. Brown Journal of Applied Physics 78 (3)-- August 1, 1995 ...[Visit Journal] Lattice‐matched p-doped GaAs–Ga_0.51In_0.49P quantum well intersub‐band photodetectors with three different well widths have been grown on GaAs substrates by metal‐organic chemical‐vapor deposition and fabricated into mesa structures. The photoresponse cutoff wavelength varies between 3.5 and 5.5 μm by decreasing the well width from 50 down to 25 Å. Dark current measurements as a function of temperature reveal activation energies for thermionic emission that closely correspond to measured cutoff wavelengths. Experimental results are in reasonable agreement with Kronig–Penney calculations. [reprint (PDF)]
17.	Temperature dependence of threshold current density J_th and differential efficiency of High Power InGaAsP/GaAs ( λ = 0.8 μm) lasers H. Yi, J. Diaz, I. Eliashevich, M. Stanton, M. Erdtmann, X. He, L. Wang, and M. Razeghi Applied Physics Letters 66 (3)-- January 16, 1995 ...[Visit Journal] An experimental and theoretical study on temperature dependence of the threshold current density J_th and differential efficiency ηd for the InGaAsP/GaAs laser diodes emitting at λ=0.8 μm was performed. Threshold current density J_th increases and differential efficiency η_d decreases as temperature is increased mainly because of thermal broadening of the gain spectrum. However, the measured temperature dependence of J_th and η_d could not be explained when only this effect was considered. In this letter, the temperature dependence of momentum relaxation rate ℏ/τ of carriers was investigated by performing the photoluminescence study. At high temperature, increase of the momentum relaxation rate ℏ/τ leads to reduction of the gain and mobility and increase of the optical loss, causing higher J_th and lower η_d as experimentally observed. The resulting theoretical model provides a good explanation for the mechanism of the increase of J_th and decrease of η_d. [reprint (PDF)]
17.	Persistent photoconductivity and the quantized Hall effect in In0.53Ga0.47As/InP heterostructures H. P. Wei; D. C. Tsui; M. Razeghi H. P. Wei, D. C. Tsui, M. Razeghi; Persistent photoconductivity and the quantized Hall effect in In0.53Ga0.47As/InP heterostructures. Appl. Phys. Lett. 15 September 1984; 45 (6): 666–668.-- September 15, 1984 ...[Visit Journal] A persistent photoconductivity is observed in the transport of the high mobility two‐dimensional electron gas in In0.53Ga0.47 As/InP heterostructures. Low field Hall measurements from 300 to 4.2 K and the quantized Hall effect in the high field limit are studied with radiation from visible and infrared light‐emitting diodes. Our results demonstrate conclusively that the effect is due to photogeneration of electron‐hole pairs in the heterostructure and trapping of holes in the In0.53Ga0.47 As. [reprint (PDF)]
17.	High power broad area quantum cascade lasers Y. Bai, S. Slivken, S.R. Darvish, A. Haddadi, B. Gokden and M. Razeghi Applied Physics Letters, Vol. 95, No. 22, p. 221104-1-- November 30, 2009 ...[Visit Journal] Broad area quantum cascade lasers (QCLs) are studied with ridge widths up to 400 µm, in room temperature pulsed mode operation at an emission wavelength around 4.45 µm. The peak output power scales linearly with the ridge width. A maximum total peak output power of 120 W is obtained from a single 400-µm-wide device with a cavity length of 3 mm. A stable far field emission characteristic is observed with dual lobes at ±38° for all tested devices, which suggests that these broad area QCLs are highly resistant to filamentation. [reprint (PDF)]

Page 17 of 31: Prev << 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 >> Next (768 Items)