Properties of InGaN blue laser diodes grown on bulk GaN substrates (original) (raw)
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Low dislocation density, high power InGaN laser diodes
MRS Internet Journal of Nitride Semiconductor Research, 2004
We used single crystals of GaN, obtained from high-pressure synthesis, as substrates for Metalorganics Vapor Phase Epitaxy growth of violet and UV laser diodes. The use of high-quality bulk GaN leads to the decrease of the dislocation density to the low level of 105 cm−2, i.e. two orders of magnitude better than typical for the Epitaxial Lateral Overgrowth laser structures fabricated on sapphire. The low density and homogeneous distribution of defects in our structures enables the realization of broad stripe laser diodes. We demonstrate that our laser diodes, having 15 μm wide stripes, are able to emit 1.3-1.9 W per facet (50% reflectivity) in 30 ns long pulses. This result, which is among the best ever reported for nitride lasers, opens the path for the development of a new generation of high power laser diodes.
Properties of violet laser diodes grown on bulk GaN substrates
Proc. of SPIE …, 2005
High pressure grown GaN bulk crystals, because of their low defect density, are atractive for the use as substrates for blue-violet laser diode fabrication. These laser diodes are characterized by a low density of dislocations (8⋅ 104-1⋅ 105 cm-2) and thus they ...
Blue-Laser Structures Grown on Bulk GaN Crystals
physica status solidi (a), 2002
Room temperature (RT) pulsed operation of blue (402-427 nm) InGaN multi-quantum well (MQW) structure laser diodes (LDs) grown on bulk GaN crystals have been demonstrated. Substrate crystals were grown with the high nitrogen pressure and high temperature solution method. After substrate preparation the laser structures were grown by the low pressure MOVPE process. The LD structures are fully strained on the whole area of GaN crystals, without mismatch-related defects, being confirmed by X-ray diffraction, atomic force microscopy (AFM), and transmission electron microscopy (TEM). Stripe geometry cavity has a contact area of 10 Â 500 mm 2 . The mirror facets were cleaved and coated with reflection dielectric layers.
Japanese Journal of Applied Physics, 2005
We demonstrate a double heterostructure (DH) nitride laser diode (LD) with an untypically wide 9.5 nm InGaN active region instead of the commonly used narrow InGaN quantum wells. Structures were grown on bulk GaN, which ensures low dislocation densities and therefore low concentrations of nonradiative recombination centers. The efficient screening of polarization induced electric fields in the structures under investigation, which contained heavily (1 Â 10 19 cm À3 ) Si doped barriers, was demonstrated by means of hydrostatic pressure dependent photoluminescence measurements on a simplified sample with identical active region. Since the detrimental separation of carriers by electric fields becomes more pronounced for wider InGaN active regions, efficient screening of polarization induced electric fields is essential for the investigated heterostructures. Optical and electrical parameters of this LD were comparable to those of comparable devices with typical QWs of $4 nm as active region. We observed a high thermal stability of the photoluminescence intensity and, via timeresolved photoluminescence, a relatively temperature-independent radiative decay time. These observations support the significance of carrier localization phenomena for the radiative recombination processes of the investigated structure. The implications of these results for DH LD structures are discussed.
Secrets of GaN substrates properties for high luminousity of InGaN quantum wells
Violet and blue Laser diodes, as well as highly efficient high-power Light Emitting Diodes (including any UV emitters) can be constructed using low-dislocation-density freestanding GaN substrates, either produced as thick HVPE layers on foreign substrates, or using direct methods of crystallization as ammonothermal one or high pressure growth from the nitrogen solution in gallium. This paper shows some of the most most important issues concerning application of such substrates. The first issue is the choice of the substrate thickness influencing the accommodation of strain, cracking and bowing of the samples. In this point, a new way of prestressing the substrate by lateral patterning will be presented. The second issue is the surface preparation either by mechanical polishing and reactive ion etching, or mechano-chemical polishing, in particular, a distribution of defects revealed by chemical etching will be discussed. Finally, the problem of substrate misorientation influencing the further morphology and indium incorporation into InGaN quantum wells will be shown. For higher misorientation of the substrates, the incorporation of indium decreases , but at the same time, the fluctuations of indium increase giving blue-shifted, weaker and broader photoluminescence peaks.
Fabrication and properties of GaN-based lasers
Journal of Crystal Growth, 2008
In this paper we will discuss the application of almost dislocation-free, high-pressure grown gallium nitride bulk crystals as a substrate for the epitaxy of GaN/InGaN/AlGaN laser diode structures. We show that these laser diodes may have very low dislocation densities (even down to 8 Â 10 4 cm À2 ). These dislocations appear during the growth of the laser structure as a result of the combined effect of strain and perturbation of the atomic step flow. We show also that the lifetime of these devices seems to be dependent on operating current via the increasing junction temperature.
Journal of Applied Physics, 2013
Semipolar oriented laser diodes (LDs) have fundamental advantages over c-plane oriented LDs, however, the thickness and composition of InGaN waveguiding layers and AlGaN cladding are limited by the onset of stress relaxation via threading dislocation glide on the c-plane slip system. Limited area epitaxy minimizes misfit dislocation (MD) formation by preventing pre-existing TDs from entering a patterned mesa. We examine the effects of mesa height and facet evolution for LAE grown strained layers. Significant MD formation was suppressed by at least a factor of four for Al 0.1 Ga 0.9 N/GaN superlattices, enabling AlGaN-clad structures similar to those used in c-plane LDs. We then demonstrate AlGaN-clad blue (456 nm) LDs with threshold current density (J th) of 4.5 kA/cm 2 and GaN-clad true green (523 nm) LDs with J th of 12 kA/cm 2. TEM measurements of the green LD confirm reduction of MD densities with reduction of MD run length. LAE is effective for improving the optical confinement factor of semipolar LDs and offers a glimpse of the design space that may soon be available using low TD density bulk GaN substrates. V
High-power and long-lifetime InGaN blue–violet laser diodes grown by molecular beam epitaxy
Electronics Letters, 2008
InGaN 405 nm multiple quantum well laser diodes grown by molecular beam epitaxy (MBE) with a continuous-wave (CW) lifetime of up to 42 h are reported. The CW threshold current density of the ridge waveguide laser diodes is 3.6 kA/cm 2 and the slope efficiency for uncoated facets is 0.42 W/A per facet with a maximum CW output power of 45 mW per facet. Statistical variation of CW lifetime with dissipated power is presented for MBE-grown laser diodes from five different wafers.
Applied Physics Express, 2008
Semipolar ð11 22Þ plane III-nitride laser diodes (LDs) were realized on low extended defect density semipolar ð11 22Þ GaN bulk substrates. The LD structures were grown by conventional atmospheric-pressure metal organic chemical vapor deposition (MOCVD), using conditions similar to that of c-plane nitride device growth. The mirror facet for a laser cavity was formed by dry-etching of III-V nitride films without cleaving. Stimulated emission was observed at 426.9 nm with a full width at half maximum (FWHM) of less than 1 nm. The ð11 22Þ plane laser diode had threshold currents (I th) of 306 mA, corresponding to a threshold current densities (J th) of 12.8 kA/cm 2 .
Secrets of GaN substrates properties for high luminousity of InGaN quantum wells
Light-Emitting Diodes: Research, Manufacturing, and Applications XII, 2008
Violet and blue Laser diodes, as well as highly efficient high-power Light Emitting Diodes (including any UV emitters) can be constructed using low-dislocation-density freestanding GaN substrates, either produced as thick HVPE layers on foreign substrates, or using direct methods of crystallization as ammonothermal one or high pressure growth from the nitrogen solution in gallium. This paper shows some of the most most important issues concerning application of such substrates. The first issue is the choice of the substrate thickness influencing the accommodation of strain, cracking and bowing of the samples. In this point, a new way of prestressing the substrate by lateral patterning will be presented. The second issue is the surface preparation either by mechanical polishing and reactive ion etching, or mechano-chemical polishing, in particular, a distribution of defects revealed by chemical etching will be discussed. Finally, the problem of substrate misorientation influencing the further morphology and indium incorporation into InGaN quantum wells will be shown. For higher misorientation of the substrates, the incorporation of indium decreases , but at the same time, the fluctuations of indium increase giving blue-shifted, weaker and broader photoluminescence peaks.