Fabrication, characterization, and applications of high-performance AlGaAs-based buried-heterostructure diode lasers (original) (raw)
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Applied Physics Letters, 1989
We report on low threshold current strained InGaAs/AlGaAs single quantum well lasers grown by molecular beam epitaxy. Broad-area threshold current densities of 114 A/cm2 at 990 nm were measured for 1540-μm-long lasers. Threshold currents of 2.4 mA at 950 nm were obtained for an uncoated buried-heterostructure device with a 2-μm-wide stripe and 425-μm-long cavity. With reflective coatings the best device showed 0.9 mA threshold current (L=225 μm). Preliminary modulation measurements show bandwidths up to 5.5 GHz limited by the detector response.
AlGaAs/InGaAs buried heterostructure laser diodes for pumping solid state lasers
1995 International Semiconductor Conference. CAS '95 Proceedings, 1995
AGaAshnGaAs buried heterostmcture laser diodes emitting at 960 m for pumping solid state lasers have been fabricated and their optical md thennal characteristics have been studied. Cylindrical microlenses were used for obtaining equd divergence angles in both planes, perpendicular and parallel to the active layer plane at 1 W of CW operation optical power. The thermal resistance, active layer and mirror temperatures have been determined as well.
Optica Applicata
A technology of high power, continuous-wave (CW) semiconductor lasers has been elaborated. AlGaAs/InGaAs/GaAs heterostructures, grown by molecular beam epitaxy (MBE), were used to fabricate laser diodes. The active region of laser diode was formed as strained, 8 nm thick, quantum well (QW) InGaAs layer. The AlGaAs layers of graded composition and graded refractive index (GRIN) formed the waveguide. Lasers were processed into wide stripe (W = 100 µm) mesas and were mounted on copper submounts and Peltier thermoelements in the standard TO-3 transistor housing. For stabilization of laser output, a silicon photodiode was placed next to a laser chip in the same case. Typical threshold current densities were 150 A/cm 2 , and the quantum efficiencies were of the order of 0.8 W/A. Lasers may work in pulsed regime as well as in CW regime with guaranteed optical power of 1 W at 300 K. The record threshold current densities achieved for 700 µm cavity were as low as 130 A/cm 2 and the characteristic temperature was T 0 = 200 K.
MOCVD growth and characterization of AlGaInN multiple quantum well heterostructures and laser diodes
Vertical mirrors have been fabricated with chemically assisted ion beam etching (CAIBE) on OMVPE grown InGaN/AlGaN laser diode structures. AFM measurements show that smooth vertical sidewalls are obtained which exhibit a root mean squared (rms) roughness of only 40—60 A. The inclination angle of the etched mirrors is within +-2° of vertical, as SEM studies indicate. Photopumping measurements reveal that the reflectivity of the etched mirrors corresponds to 60—70% of the value for an ideal GaN/air interface. The reduced reflectivity may be due to surface roughness, a slight tilt in the facet angle, and the excitation of higher-order transverse waveguide modes in the laser structure.
IEEE Journal of Selected Topics in Quantum Electronics, 2013
We discuss the wafer design and fabrication process for the 1.3-μm-wavelength AlGaInAs/InP transistor lasers, and the structural dependence of lasing and the electrical characteristics are shown. We particularly focus on the base structure, and the thickness and width dependence are numerically and experimentally analyzed. A thicker base layer resulted in lower optical confinement factor in the quantum wells (QWs), higher optical loss, and lower current gain. In addition, a wider base width caused leak current recombination outside the QWs. By modifying the structure of an n-p-n TL, it was possible to simultaneously realize room-temperature continuous-wave lasing and transistor operation. Index Terms-AlGaInAs/InP, quantum-well (QW) laser, transistor laser (TL). I. INTRODUCTION T ODAY, data traffic is rapidly increasing, and the demand for high-speed data transmission is strong. Optical communications are widely used in intercontinental or intercity communications, fiber-to-the-home, and interconnections between individual computers to transmit high-bit-rate data. To address these demands, the 40-100-Gb/s Ethernet systems were standardized in 2010 [1] and the beyond 100 GbE is currently under consideration. In these systems, the optical signal sources are among the key devices. In recent high-speed modules of over 25 Gb/s, electroabsorption-modulated lasers have been typically used because they meet the requirements of speed and compactness [2]. However, direct-modulation lasers could be more attractive if they can meet the modulation-speed requirement in short-distance optical communication systems [3], [4]. In this case, the modulation speed of conventional laser diodes (LDs) is limited to approximately 40 Gb/s due to several factors, including the damping effect caused by carrier transport [5], [6].
Journal of The Optical Society of America B-optical Physics, 2009
Detailed experimental characterization is performed for 1550 nm semi-insulating regrown buried heterostructure Fabry-Perot (FP) lasers having 20 InGaAsP / InGaAlAs strain-balanced quantum wells (QWs) in the active region. Light-current-voltage performance, electrical impedance, small-signal response below and above threshold, amplified spontaneous emission spectrum below threshold and relative intensity noise spectrum are measured. Different laser parameters such as external differential quantum efficiency d , background optical loss ␣ i , K-factor, D-factor, characteristic temperature T 0 , differential gain dg /dn, gain-compression factor ⑀, carrier density versus current, differential carrier lifetime d , optical gain spectrum below threshold, and chirp parameter ␣ are extracted from these measurements. The FP lasers exhibited a high T 0 ͑78-86.5°C͒ and very high-resonance frequency ͑23.7 GHz͒. The results indicate that appropriately designed lasers having a large number of InGaAsP well/InGaAlAs barrier QWs with shallow valence-band discontinuity can be useful for uncooled high-speed direct-modulated laser applications.
Semiconductors, 2010
InGaAs/GaAs/AlGaAs laser heterostructures are grown by MOCVD epitaxy on GaAs substrates. Mesastripe laser diodes with an aperture of 100 μm emitting at a wavelength of 1190 nm are fabricated. It is shown that, in these lasers, the active region is relaxed, which manifests itself in the spread of attainable max imal power for various lasers obtained from the same heterostructure. The maximal emission power in a CW mode of lasing for such lasers was 5.5 W per mirror.
Applied Physics Letters, 1996
We have studied the effects of substrate misorientation on the growth of strained-layer In 0.18 Ga 0.82 As quantum well laser structures with InGaAsP confinement layers and In 0.5 Ga 0.5 P cladding layers lattice matched to a GaAs substrate. Low-temperature photoluminescence ͑PL͒ and atomic force microscopy ͑AFM͒ provide evidence of a strong substrate-orientation dependence of the interface structure. The surface morphology of the InGaAs quantum well is found to be determined primarily by the underlying InGaAsP confinement layer. Structures grown on exact-͑100͒ oriented substrates exhibit three-dimensional island surface morphology, whereas growths on ͑100͒ substrates oriented 2°towards ͓110͔ exhibit high surface roughness, possibly due to step bunching. These observations correlate well with previously reported device performance from strained quantum well laser diodes in the InGaAs/InGaAsP/InGaP material system, and can serve as a tool to optimize device performance.
Optical and electrical characteristics of AlGaAs lasers with separate confinement heterostructures are modeled by using Synopsys's Sentaurus TCAD, and open source software. The results for cases of 2-QW (2 Quantum Wells) and 3-QW structures are compared with these for 1-QW. A significant improvement of useful laser parameters is obtained by increasing the number of Quantum Wells and optimizing the width of waveguides. In particular, the maximum optical efficiency is shown to reach 88 % for a 3-QW structure with optimal width of waveguides. The width of optical intensity profile of MQW lasers increases, leading to lowering maximal light power density passing through laser facets, decreasing the risk of catastrophic damage of mirrors.
810-nm InGaAlAs/AlGaAs double quantum well semiconductor lasers with asymmetric waveguide structures
Chinese Optics Letters, 2008
The 810-nm InGaAlAs/AlGaAs double quantum well (QW) semiconductor lasers with asymmetric waveguide structures, grown by molecular beam epitaxy, show high quantum efficiency and high-power conversion efficiency at continuous-wave (CW) power output. The threshold current density and slope efficiency of the device are 180 A/cm 2 and 1.3 W/A, respectively. The internal loss and the internal quantum efficiency are 1.7 cm −1 and 93%, respectively. The 70% maximum power conversion efficiency is achieved with narrow far-field patterns.