Grating overgrowth and defect structures in distributed-feedback-buried heterostructure laser diodes

Chu, S. N. G.; Tanbun‐Ek, T.; Logan, Andrew S.; Vandenberg, J. M.; Sciortino, P.F.; Wisk, P.; Pernell, T. L.

doi:10.1109/2944.640640

Cited by 14 publications

(13 citation statements)

References 31 publications

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“…This observation is in sharp contrast to InGaAsP/InP-based infrared DFB lasers, where the grooved interface serves as starting point for numerous dislocations [7]. However, we found also that only 3 out of 5 QWs were etched during the grating etch process; this conclusion confirmed that our device was a complex-coupled rather than a purely gain-coupled DFB laser.…”

Section: Optically Pumped Complex Coupled Dfb Lasercontrasting

confidence: 29%

Characterization of InGaN/GaN-Based Multi-Quantum Well Distributed Feedback Lasers

Hofstetter

Thornton²,

Romano

et al. 1998

MRS Proc.

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We present a device fabrication technology and measurement results of both optically pumped and electrically injected InGaN/GaN-based distributed feedback (DFB) lasers operated at room temperature. For the optically pumped DFB laser, we demonstrate a complex coupling scheme for the first time, whereas the electrically injected device is based on normal index coupling. Threshold currents as low as 1.1 A were observed in 500 µm long and 10 µm wide devices. The 3 rd order grating providing feedback was defined holographically and dry-etched into the upper waveguiding layer by chemically-assisted ion beam etching. Even when operating these lasers considerably above threshold, a spectrally narrow emission (3.5 Å) at wavelengths around 400 nm was seen.

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Section: Optically Pumped Complex Coupled Dfb Lasercontrasting

confidence: 29%

Characterization of InGaN/GaN-Based Multi-Quantum Well Distributed Feedback Lasers

Hofstetter

Thornton²,

Romano

et al. 1998

MRS Proc.

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“…This is very different from overgrowths made with InGaAsP/InPbased infrared DFB lasers, for example, where the grooved interface serves as starting point for numerous dislocations. 8 An additional fringe contrast is observed in the area of the grating ͓Fig. 3͑a͔͒ which will be discussed below.…”

Section: Published In Applied Physicsmentioning

confidence: 95%

Structural and optical properties of epitaxially overgrown third-order gratings for InGaN/GaN-based distributed feedback lasers

Romano

Hofstetter

McCluskey

et al. 1998

Applied Physics Letters

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Laser-diode heterostructures of InGaAlN containing a third-order diffraction grating for distributed optical feedback have been examined with transmission electron microscopy ͑TEM͒ and scanning electron microscopy ͑SEM͒. The grating was defined holographically and etched by chemically assisted ion-beam etching into the upper GaN confinement layer of the laser structure. After the etch step, it was overgrown with an Al 0.08 Ga 0.92 N upper cladding layer. Threading dislocations were present that initiated at the sapphire substrate, but no new dislocations were observed at the grating/Al 0.08 Ga 0.92 N interface. A comparison of TEM and SEM micrographs reveals that there is a compositional gradient in the AlGaN upper cladding layer; however, calculations show that it did not reduce the optical coupling coefficient of the grating.Within the last couple of years, research on semiconductor lasers with emission wavelengths around 400 nm has received a great deal of attention. Recent milestones in the development of nitride-based light emitters have been the demonstration of high-brightness blue/green light emitting diodes and both pulsed and continuous-wave laser operation at room temperature. [1][2][3][4][5] Mainly for the purpose of overcoming difficulties in high-quality mirror fabrication, but also in order to improve mode selection and wavelength stability, distributed feedback ͑DFB͒ blue lasers have been demonstrated recently.6 Etching and regrowth of the grating, which typically completes the device structure, is a major obstacle for the fabrication of DFB lasers in material systems other than the nitrides. The strong chemical bonds between gallium and nitrogen result in a very stable and chemically inert surface, compared to GaAs materials for example, where oxides are readily formed on the surface.In this letter, we present a structural evaluation of a third-order diffraction grating from InGaN/GaN-based DFB lasers. The grating was defined by holography and etched into the GaN upper confinement layer by chemically assisted ion-beam etching ͑CAIBE͒. After etching, it was overgrown with an Al 0.08 Ga 0.92 N upper cladding layer and a GaN contact layer. We compare scanning electron microscopy ͑SEM͒ and transmission electron microscopy ͑TEM͒ cross sections of the grating before and after overgrowth. Based on these observations, we estimate how an effective alteration of the grating profile due to a compositional gradient might affect the grating's coupling coefficient and thus the threshold gain of the laser.The fabrication of these devices relied on growing a 4 m thick n-type GaN:Si layer on C-face sapphire. On top of this layer, we grew a 500 nm thick, n-type Al 0.08 Ga 0.92 N:Si lower cladding layer, a 100 nm thick n-type GaN:Si lower waveguiding layer, an active region with five 3.5 nm thick In 0.1 Ga 0.9 N quantum wells and 9.0 nm thick GaN barriers, and a 180 nm thick p-type GaN:Mg upper waveguiding layer. More details about growth conditions and doping levels can be found in Ref. 5. The thicknesses of the ...

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“…In the process of growing heterostructure wafers for DFB-LDs, the resulting corrugation height is decreased as compared to the initial one. This is due to the mass-transport phenomena on an InP grating, and because the arsenic partial pressure into the metal-organic vapor-phase epitaxy (MOVPE) growth ambient is optimized to control this deformation [13][14][15][16][17]. The measurement of the grating profile is very important for actual device production.…”

Section: Introductionmentioning

confidence: 99%

Scatterometry measurement of ingaasp/inp grating for DFB lasers grown with MOVPE

Muroya

Katoh

Makino

et al. 2007

Journal of Crystal Growth

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Grating overgrowth and defect structures in distributed-feedback-buried heterostructure laser diodes

Cited by 14 publications

References 31 publications

Characterization of InGaN/GaN-Based Multi-Quantum Well Distributed Feedback Lasers

Characterization of InGaN/GaN-Based Multi-Quantum Well Distributed Feedback Lasers

Structural and optical properties of epitaxially overgrown third-order gratings for InGaN/GaN-based distributed feedback lasers

Scatterometry measurement of ingaasp/inp grating for DFB lasers grown with MOVPE

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