Buried Heterostructure Lasers Research Articles

Failure Analysis of InP-Based Edge-Emitting Buried Heterostructure Laser Diodes Degraded by Forward-Biased Electrostatic Discharge Tests

We investigated the forward-biased electrostatic discharge (ESD)-induced degradation that is one of the important reliability issues for InP-based edge-emitting buried heterostructure laser diodes. Although it has been suggested that the degradation mechanism is related to optical damage, the detailed mechanism has not been established. Thus, we carried out failure analysis. Two elliptically shaped degraded regions, which were introduced by the first and second ESD pulses, were observed in an active layer. A peculiar chain-like degradation was created along the longitudinal axis. This degradation was caused by light absorption at an active layer. We also investigated the relationship between forward-biased ESD tolerance and an aging test. We observed a decrease in tolerance as a result of the aging test for laser diodes with cleaved facets. This decrease was sufficiently suppressed by facet coating. We identified two reasons why facet coating is important. One is to obtain sufficient ESD tolerance under initial conditions, and the other is to suppress the decrease in ESD tolerance during aging.

Relationship between Reverse-Biased Electrostatic-Discharge Tolerance and Aging of GaInAsP/InP Buried-Heterostructure Laser Diodes

Degradation due to electrostatic discharge (ESD) is an important reliability issue for GaInAsP/InP buried-heterostructure laser diodes (LDs). Although this degradation mechanism has been previously discussed, the relationship between ESD tolerance and aging has not been investigated. For forward-biased ESD, the degradation mechanism is similar to that of catastrophic optical damage. Therefore, ESD tolerance can be assumed to decrease during an aging test. However, the relationship between reverse-biased ESD tolerance and aging is less clear. We investigated this relationship, focusing particularly on reverse bias, and observed a decrease in ESD tolerance owing to aging. Specifically, the ESD tolerances decreased by approximately 30 and 70% for facet-coated and uncoated GaInAsP/InP Fabry–Perot LDs, respectively, as a result of aging longer than 3000 h. We determined that facet coating is effective in suppressing the reduction in ESD tolerance caused by aging.

Size Effect on ESD Threshold and Degradation Behavior of InP Buried Heterostructure Semiconductor Lasers

Optoelectronic components such as laser diodes and light-emitting diodes are vulnerable to electrostatic dis- charge (ESD) and electrical overstress (EOS). In this paper, we extensively study the size effect on ESD performance of buried heterostructure (BH) distributed feedback (DFB) InGaAsP/InP lasers. We show that the ESD threshold and degra- dation behavior of BH lasers are correlated with the cavity length and contact width. The ESD threshold increases linearly with increasing cavity length and contact width. For the ESD degradation behavior, the occurrence frequency of hard deg- radation, a behavior characterized with a sudden jump in threshold current during the ESD voltage ramp, decreases with increasing cavity length. We also show that the dielectric layer is influential in ESD performance. The physical mecha- nisms of the ESD behavior will also be discussed.

Thermal analysis of buried heterostructure quantum cascade lasers for long‐wavelength infrared emission using 2D anisotropic heat‐dissipation model

AbstractWe have theoretically investigated and compared the thermal characteristics of γ ∼ 10.6 μm InGaAs/InAlAs/InP buried heterostructure (BH) quantum cascade lasers (QCLs) with different heat‐sinking configurations by a steady‐state heat‐transfer analysis. The heat‐source densities were obtained from laser threshold power densities measured experimentally under room‐temperature continuous‐wave mode. The two‐dimensional anisotropic heat‐dissipation model was used to calculate the temperature distribution, heat flux, and thermal conductance (Gth) inside the device. For good thermal characteristics, the QCLs in the long‐wavelength infrared region require the relatively narrow BH structure in combination with epilayer‐down bonding due to thick active core/cladding layers and high insulator losses. The single‐ridge BH structure results in slightly higher thermal conductance by ∼2–4% than the double‐channel (DC) ridge BH structure. For W = 12 μm with 5 μm thick electroplated Au, the single‐ridge BH laser with epilayer‐down bonding exhibited the highest Gth value of 201.9 W/K cm2, i.e. increased by nearly 36% with respect to the epilayer‐up bonded DC ridge waveguide laser. This value is improved by ∼50% and ∼62% with respect to the single‐ridge BH laser and DC ridge waveguide laser with W = 20 μm in the epilayer‐up bonding scheme, respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

1.3-$\mu$m AlGaInAs Multiple-Quantum-Well Semi-insulating Buried-Heterostructure Distributed-Feedback Lasers for High-Speed Direct Modulation

This paper describes 1.3-mum AlGaInAs multiple-quantum-well semi-insulating buried-heterostructure distributed-feedback lasers for high-speed direct modulation. Combination of large differential gain AlGaInAs quantum wells and semi-insulating buried-heterostructure for reduction of active region achieved 25 and 40 Gb/s direct modulation with the device having the cavity length of 150 mum. The device whose Bragg wavelength is longer than gain peak wavelength showed 25 Gb/s direct modulation characteristics with superior temperature characteristics. The relaxation oscillation frequency of this device was 15 GHz and higher up to 70degC. Clear eye-opening was observed and single-mode fiber transmission experiments showed low power penalty up to 70degC. With the device of negative detuning with larger differential gain, we achieved 40 Gb/s direct modulation. This device showed high relaxation oscillation frequency and slope of 20.5 GHz and 3.2 GHz/mA1/2, respectively. The 40 Gb/s eye opened clearly at 25degC and eye-opening was observed up to 50degC.

Degradation Behavior of 850 nm AlGaAs/GaAs Oxide VCSELs Suffered from Electrostatic Discharge

AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract The effect of forward and reverse electrostatic discharge (ESD) on the electro-optical characteristics of oxide vertical-cavity surface-emitting lasers is investigated using a human body model for the purpose of understanding degradation behavior. Forward ESD-induced degradation is complicated, showing three degradation phases depending on ESD voltage, while reverse ESD-induced degradation is relatively simple, exhibiting two phases of degradation divided by a sudden distinctive change in electro-optical characteristics. We demonstrate that the increase in the threshold current is mainly due to the increase in leakage current, nonradiative recombination current, and optical loss. The decrease in the slope efficiency is mainly due to the increase in optical loss. References 1H. Mizuno et al., “Replicated Polymeric Optical Waveguide Devices with Large Core Connectable on Plastic Optical Fiber Using Thermo-plastic and Thermo-curable Resins,” J. Lightwave Technol., Vol. 24, no. 2, Feb. 2006, pp. 919– 926. 2Å. Haglund et al., “Comparative Study of the High-Speed Digital Modulation Performance of Single- and Multi-mode Oxide Confined VCSELs for Free Space Optical Interconnects,” Proc. SPIE, Vol. 4649, 2002, pp. 272– 280. 3M. Gruber, R. Kerssenfischer, and J. Jahns, “Planar-Integrated Free-Space Optical Fan-Out Module for MT-Connected Fiber Ribbons,” J. Lightwave Technol., Vol. 22, no. 9, Sept. 2004, pp. 2218– 2222. 4A. Chow et al., “Smart Optical Sensors for Industrial and Consumer Applications,” Proc. ESTC, Sept. 2006, pp. 101– 106. 5L.F. DeChiaro and C.J. Sandroff, “Improvement in Electrostatic Discharge Performance of InGaAsP Semiconductor Lasers by Facet Passivation,” IEEE Trans. Electron Device, Vol. 39, no. 3, Mar. 1992, pp. 561– 565 6J. Jeong, K.H. Park, and H.M. Park, “Wavelength Shifts of 1.5-mm DFB Lasers Due to Human-Body-Model Electronic Discharge Followed by Accelerated Aging Experiments,” J. Lightwave Technol., Vol. 13, no. 2, Feb. 1995, pp. 186– 190. 7H. Ichikawa et al., “Analysis on ESD-Induced Degradation of GaInAsP LD,” SEI Technical Review, no. 64, Apr. 2007, pp. 9– 14. 8J.-S. Huang, T. Olson, and E. Isip, “Human-Body-Model Electrostatic Discharge and Electrical-Overstress Studies of Buried-Heterostructure Semiconductor Lasers,” IEEE Trans. Device and Mater. Rel., Vol. 7, no. 3, Sept. 2007, pp. 453– 461. 9B. M. Hawkins et al., “Reliability of Various Size Oxide Aperture VCSELs,” Proc. ECTC, May 2002, pp. 540– 550. 10S.A. McHugo et al., “Characterization of Failure Mechanisms for Oxide VCSELs,” Proc. SPIE, Vol. 4994, 2003, pp. 55– 66. 11”Sensitivity Testing, Human Body Model, Component Level,” ESD Association, Rome, ESD STM5.1, 2001. 12D. Mathes et al., “AOC Moving Forward: The Impact of Materials Behavior,” Proc. SPIE, Vol. 4994, 2003, pp. 162– 172. 13J. Krueger et al., “Studies of ESD-Related Failure Patterns of Agilent Oxide VCSELs,” Proc. SPIE, Vol. 4994, 2003, pp. 162– 172. 14C. Helms et al., “Reliability of Oxide VCSELs at Emcore,” Proc. SPIE, Vol. 5364, 2004, pp. 183– 189. 15H.C. Neitzert, A. Piccirillo, and B. Gobbi, “Sensitivity of Proton Implanted VCSELs to Electrostatic Discharge Pulses,” IEEE J. Quantum Electron., Vol. 7, no. 2, Mar. 2001, pp. 231– 241. 16P.D. Wright, “Electrical Derivative Characteristics of InGaAsP Buried Heterostructure Lasers,” J. Appl. Phys., Vol. 61, Mar. 1987, pp. 1720– 1724. 17A. Ramaswamy et al., “Electrical Characteristics of Proton-Implanted Vertical-Cavity Surface-Emitting Lasers,” IEEE J. Quantum Electron., Vol. 34, no. 11, Nov. 1998, pp. 2233– 2240. 18P.A. Barnes and T.L. Paoli, “Derivative Measurements of the Current-Voltage Characteristics of Double-Heterostructure Injection Lasers,” J. Quantum Electron., Vol. QE-12, Oct. 1976, pp. 633– 639. 19W.B. Joyce and R.W. Dixon, “Electrical Characterization of Heterostructure Laser,” J. Appl. Phys., Vol. 49, July 1978, pp. 3719– 3728. Citing Literature Volume30, Issue6December 2008Pages 833-843 ReferencesRelatedInformation

Quantum cascade lasers with integrated plasmonic antenna-array collimators

We demonstrated in simulations and experiments that by defining a properly designed two-dimensional metallic aperture-grating structure on the facet of quantum cascade lasers, a small beam divergence angle can be achieved in directions both perpendicular and parallel to the laser waveguide layers (denoted as theta perpendicular and theta parallel, respectively). Beam divergence angles as small as theta perpendicular=2.7 degrees and theta parallel=3.7 degrees have been demonstrated. This is a reduction by a factor of approximately 30 and approximately 10, respectively, compared to those of the original lasers emitting at a wavelength of 8.06 microm. The devices preserve good room temperature performance with output power as high as approximately 55% of that of the original unpatterned lasers. We studied in detail the trade-off between beam divergence and power throughput for the fabricated devices. We demonstrated plasmonic collimation for buried heterostructure lasers and ridge lasers; devices with different waveguide structures but with the same plasmonic collimator design showed similar performance. We also studied a device patterned with a "spider's web" pattern, which gives us insight into the distribution of surface plasmons on the laser facet.

Thermal analysis of InP-based quantum cascade lasers for efficient heat dissipation

We have theoretically investigated the thermal characteristics of double-channel ridge–waveguide InGaAs/InAlAs/InP quantum cascade lasers (QCLs) using a two-dimensional heat dissipation model. The temperature distribution, heat flow, and thermal conductance (Gth) of QCLs were obtained through the thermal simulation. A thick electroplated Au around the laser ridges helps to improve the heat dissipation from devices, being good enough to substitute the buried heterostructure (BH) by InP regrowth for epilayer-up bonded lasers. The effects of the device geometry (i.e., ridge width and cavity length) on the Gth of QCLs were investigated. With 5 μm thick electroplated Au, the Gth is increased with the decrease of ridge width, indicating an improvement from Gth=177 W/K⋅cm2 at W=40 μm to Gth=301 W/K⋅cm2 at W=9 μm for 2 mm long lasers. For the 9 μm×2 mm epilayer-down bonded laser with 5 μm thick electroplated Au, the use of InP contact layer leads to a further improvement of 13% in Gth, and it was totally raised by 45% corresponding to 436 W/K⋅cm2 compared to the epilayer-up bonded laser with InGaAs contact layer. It is found that the epilayer-down bonded 9 μm wide BH laser with InP contact layer leads to the highest Gth=449 W/K⋅cm2. The theoretical results were also compared with available obtained experimentally data.

In Ga As P ∕ In P buried-heterostructure laser diodes grown on InP using molecular beam epitaxy and metal-organic chemical vapor deposition

Buried-heterostructure (BH) laser diodes were fabricated using both molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). MBE was used to grow the active region and the p-type cladding and contact structures while MOCVD was used for the Fe-doped, blocking layer structures. Using this method, devices were fabricated which showed good performance over the temperature range of −20–85°C. Devices were demonstrated at several wavelengths including 1550 and 1610nm. Room temperature operation of the unpackaged 1610nm devices, with coated facets, demonstrated threshold currents as low as 6mA and efficiencies of 0.3mW∕mA. The same devices operating at 85°C showed threshold currents as low as 22mA and efficiencies of 0.2mW∕mA. Coaxial, fiber pigtailed devices consistently demonstrated OC-48 dispersion power penalties of less than 1.5dB for fiber spans of 100km. Preliminary device reliability shows minimal degradation. TO-56 packaged devices operating at a constant power of 6mW at 90°C for over 4000h have shown a maximum of 3% increase in operating current. The performance and excellent reliability of these devices indicate that this method can be used for the low-cost manufacture of BH distributed feedback lasers.

Nonuniform output characteristics of laser diode with wet-etched spot-size converter

We study the output characteristics of spot-size converter (SSC) integrated buried heterostructure (BH) laser diode (LD) by forming SSC with wet etching process. SSC-LD shows large chip-to-chip variation in threshold current(Ith) and slope efficiency (eta(slope)) compared to LD without SSC. Ith and eta(slope) are closely related with each other so that the front facet eta(slope) increases while the rear facet eta(slope) decreases with Ith. Far-field angle is also found to be proportional to the front facet eta(slope). The trends observed are explained clearly by a unidirectional loss occurring when photons travel from the front to rear facet.

High-Reliable and High-Speed 1.3 $\mu$m Complex-Coupled Distributed Feedback Buried-Heterostructure Laser Diodes With Fe-Doped InGaAsP/InP Hybrid Grating Layers Grown by MOCVD

In this paper, we report the fabrication of high-reliability and high-speed 1.3 mum complex-coupled distributed feedback (CC-DFB) buried heterostructure (BH) laser diodes (LDs) with Fe-doped InGaAsP/InP hybrid grating layers. High optical coupling coefficient and eminent current confining ability are accomplished by combining the Fe-doped InGaAsP/InP current-blocking-grating (CBG) layers to provide both the distributed-feedback index-and gain-coupling coefficients. Besides, the narrow-stripe BH LDs are implemented by burying the active region with a Fe-doped InP current-blocking layer during the epitaxial regrowth. The fabricated CBG CC-DFB BH LDs at 20degC shows a low threshold current of 5.3 mA, a maximum light output power of 36 mW at 100 mA, a high slope efficiency of 0.41 mW/mA, and a side-mode suppression ratio (SMSR) of 42 dB at twice the threshold. In addition, these LDs exhibit a maximum operation temperature of 125degC, an extremely low threshold current of 15.8 mA at 90degC, a small variation in slope efficient of only -1 dB in the temperature range from 20degC to 80degC, and a characteristic temperature of 77 K and 56 K between 20 degC and 60degC, and 70degC and 120degC, respectively. Furthermore, these 1.3 mum CBG CC-DFB BH LDs exhibit a high-speed characteristic up to 11.8 GHz at room temperature and an estimated median lifetime of more than 1.1 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> h or 12.5 years at 5 mW and 85degC.

Uncooled 25 Gbit/s direct modulation of semi-insulating buried-heterostructure 1.3 [micro sign]m AlGaInAs quantum-well DFB lasers

Uncooled 25 Gbit/s direct modulation of 1.3 µm DFB lasers is demonstrated. The 150 µm-long semi-insulating buried-heterostructure AlGaInAs quantum-well DFB lasers show clear eye-openings with dynamic extinction ratio of 5 dB up to 70°C. 13 km singlemode-fibre transmission experiments using the devices show low power penalty within 1.3 dB between 25 and 70°C. These characteristics are the first achievement by 1.3 µm directly modulated lasers.

Room-temperature continuous-wave operation of an external-cavity quantum cascade laser

Room-temperature, continuous-wave operation of an external-cavity quantum cascade laser (EC-QCL) is reported. Single-mode tuning range of 120 cm(-1) was achieved, from 7.96 to 8.84 microm. The gain chips utilized are based on the bound to continuum design and were fabricated as buried heterostructure lasers. Gap-free tuning (mode hops only on the external-cavity modes) is demonstrated for an antireflection-coated laser, just by grating rotation. The EC-QCL was implemented in a Littrow setup and an average power of 1.5 mW was obtained at 20 degrees C, while a peak power of 20 mW was obtained for a modified Littrow setup with the back extraction of light.

Human-Body-Model Electrostatic-Discharge and Electrical-Overstress Studies of Buried-Heterostructure Semiconductor Lasers

Optoelectronic components such as laser diodes, light-emitting diodes, and photodiodes are susceptible to electrostatic discharge (ESD) and electrical overstress (EOS). Human-body model (HBM) is the most widely adopted method for the characterization of the ESD performance. In this paper, we report a comprehensive study of the ESD and EOS characteristics of buried-heterostructure (BH) semiconductor lasers using the HBM. Threshold current, optical power, optical spectrum, and reverse-bias current are characterized during the ESD study. We show that the ESD-failure thresholds depend upon the polarity. The chip can sustain the highest ESD stress under forward bias and the lowest one under forward/reverse bias. We also show that the BH lasers exhibit two types of ESD-degradation behavior. The soft degradation is characterized by a gradual increase in the threshold current, whereas the hard degradation is identified by a sudden jump in the threshold current during the ESD voltage ramp. The ESD-degradation behavior seems to be influenced by the cavity length. The failure-analysis results show that about 27% of the ESD failure is related to facet damage. The damage regions occur at the upper laser mesa structure and form preferentially on the bond-pad side. The preferential formation of the facet damage is suggestive of current-crowding effect. We have also found that the ESD-degradation behavior is a function of the facet damage. The soft-degradation failure shows a stronger correlation with the facet damage than the hard-degradation one. Finally, we demonstrate that the ESD performance of the laser can be improved by adding a protection diode.

High Performance 1.55 μm InGaAsP Buried-Heterostructure Laser Diodes Fabricated by Single-Step MOCVD Regrowth and Self-Aligned Technique

In this article, we demonstrate a simple and low-cost method to fabricate the strained multiquantum-well buried-heterostructure (BH) laser diodes (LDs) by using the single-step metallorganic-chemical-vapor-deposition (MOCVD) regrowth and self-aligned technique. The active region is buried by the intrinsic layer which is used as the current-blocking layer as well as the electrical and optical confinement layer. The BH LDs have a calculated internal quantum efficiency of 81% and an internal loss of . The fabricated as-cleaved BH LDs exhibit a threshold current of , a maximum light output power of at , a maximum operating temperature of , and a characteristic temperature of in . The BH LDs with an as-cleaved front facet and a high reflectivity coating applied to the rear facet can increase the maximum operation temperature up to and have a light output power exceeding at and . The frequency at a bias current of is 8.0, 6.5, and at 30, 60, and , respectively. Besides, the modulation bandwidth can be extended as far as at and . These results confirm that BH LDs have the potential capacity for high-speed fiber optic applications.

Fabrication of InGaAlAs MQW buried heterostructure lasers by narrow stripe selective MOVPE

Fabrication of InGaAlAs MQW buried heterostructure (BH) lasers by narrow stripe selective MOVPE is demonstrated in this paper. High quality InGaAlAs MQWs were first grown by narrow stripe selective MOVPE without any etching process and assessed by analysing the cross sections and PL spectrums of the InGaAlAs MQWs. Furthermore, BHs were fabricated for the InGaAlAs MQW lasers by a developed unselective regrowth method, instead of conventional selective regrowth. The InGaAlAs MQW BH lasers exhibit good device characteristics, with a high internal differential quantum efficiency of 85% and a low internal loss of 6.7 cm−1. Meanwhile, narrow divergence angles of the far field pattern are obtained for the fabricated lasers.

Unselective regrowth of &lt;inline-formula&gt;&lt;math altimg="none" display="inline" overflow="scroll"&gt;&lt;mrow&gt;&lt;mn&gt;1.5&lt;/mn&gt;&lt;mtext&gt;-&lt;/mtext&gt;&lt;mi mathvariant="normal"&gt;μ&lt;/mi&gt;&lt;mi mathvariant="normal"&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/inline-formula&gt;&lt;inline-formula&gt;&lt;math altimg="none" display="inline" overflow="scroll"&gt;&lt;mrow&gt;&lt;mi&gt;InGaAsP&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/inline-formula&gt; multiple-quantum-well distributed-feedback buried heterostructure lasers

Unselective regrowth for fabricating 1.5-mu m InGaAsP multiple-quantum well (MQW) distributed-feedback (DFB) buried heterostructure (BH) lasers is developed. The experimental results exhibit superior characteristics, such as a low threshold of 8.5 mA, high slope efficiency of 0.55 mW/mA, circular-like far-field patterns, the narrow line-width of 2.5 MHz, etc. The high performance of the devices effectively proves the feasibility of the new method to fabricate buried heterostructure lasers. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

High-speed and uncooled operation of 1.3-/spl mu/m InGaAsP strain-compensated MQW BH lasers fabricated on patterned InP substrates

The fabrication and characteristics of 1.3-/spl mu/m InGaAsP strain-compensated multiquantum well (SCMQW) buried heterostructure (BH) laser diodes (LDs) grown by selective metal-organic chemical vapor epitaxy on a patterned InP substrate are demonstrated. The photoluminescence (PL) of the SCMQW active region grown on the patterned grooves has a narrow full-width at half-maximum of /spl sim/ 47 meV. The BH LDs exhibit a threshold current of 6.8 mA, a slope efficiency of 0.45 mW/mA, and a light output power exceeding 30 mW at 80 mA and 20/spl deg/C. The maximum operating temperature is 120/spl deg/C with a characteristic temperature of 72 K in 20/spl deg/C-80/spl deg/C. The 3-dB modulation bandwidth can be extended as far as 11.4 GHz under a bias level of 40 mA, and the back-to-back tests show a clear and symmetric eye diagram at 10 Gb/s with a PRBS of 2/sup 31/-1 word length and a peak-to-peak voltage of 1.08 V at 85/spl deg/C. The average increase in operational current is smaller than 0.84% after the 1500-h aging test. The mean time of the BH LDs operated at 85/spl deg/C to fail is calculated as 9/spl times/10/sup 4/ h. These BH LDs satisfy the reliability requirement for strict loop environment and 10-Gb Ethernet application without special hermetic packaging.

Cross-sectional scanning tunneling microscopy and spectroscopy of strain in buried heterostructure lasers

Cross-sectional scanning tunneling microscopy and spectroscopy have been used to probe the unreconstructed (1 1 0) surface of a commercially available buried heterostructure laser in ultra high vacuum. Complex re-growth above the non-linear blocking layers is shown to induce tensile strain in the device. Spectroscopic measurements show an increase in both the density of filled valence band states and empty conduction band states as a result of the strain, with a particularly large increase at −3.1 V. Current imaging tunneling spectroscopy measurements show an increase in the tunneling current in to and out of the strained regions at both gap voltage polarities, consistent with the spectroscopy. Moving towards tensile strain, InP is known to maintain much the same bandgap, with the split-off level and lower lying states being drawn up towards the valence band edge, consistent with the data.

High-power quantum cascade lasers grown by low-pressure metal organic vapor-phase epitaxy operating in continuous wave above 400K

High-power quantum cascade lasers (QCLs) working in continuous wave (cw) above 400K are presented. The material was grown by low-pressure metal organic vapor-phase epitaxy and processed into narrow buried heterostructure lasers. A cw output power of 204mW was obtained at 300K with an 8.38μm wavelength, 3mm long and 7.5μm wide coated laser. The device operates in cw mode above 400K, which exceeds the previous maximum cw temperature operation of QCLs by approximately 60K. Preliminary reliability data obtained by accelerated aging tests indicate a remarkable robustness of the lasers.