A Perspective on the GaN Injection Laser

Pánkové, J. I.

doi:10.1557/s1092578300001459

Cited by 13 publications

(12 citation statements)

References 7 publications

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“…Bright and efficient blue and green LEDs are in the marketplace, InGaN/GaN/AlGaN heterostructure laser diode research is progressing at a rapid pace. Many other optoelectronic and high temperature electronic devices are being contemplated [1]. These achievements are attributed mainly to the breakthroughs in the course of GaN research, such as first synthesis of GaN [2], HVPE growth of single crystalline GaN [3], first demonstration of GaN LED, invention of buffer layer technology, success in p-type conversion, as well as epitaxial lateral over growth.…”

Section: Introductionmentioning

confidence: 99%

Epitaxial Growth and Structural Characterization of Single Crystalline ZnGeN₂

Liang

Maruska

Norris

et al. 1999

MRS Internet j. nitride semicond. res.

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Section: Introductionmentioning

confidence: 99%

Epitaxial Growth and Structural Characterization of Single Crystalline ZnGeN₂

Liang

Maruska

Norris

et al. 1999

MRS Internet j. nitride semicond. res.

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“…Optical measurements of nitrides [16] [17] [18] [19] reveal, however, long tails of density of states extending deeply into the band gap. Therefore activeregion losses are mainly free-carrier losses: α A ≅ α fc,A (8) whereas optical losses in spacers contain also material losses α m,P and α m,N [20] [21]:…”

Section: The Modelmentioning

confidence: 99%

“…with an increase in an energy gap. Therefore we assume for GaN A = 1.0·10 8 GaN at room temperature was calculated in Ref. [33] (B = 0.15·10 10 cm 3 s -1 ).…”

Section: The Modelmentioning

confidence: 99%

“…The latest Nichia achievements [6] are very promising but a high density of defects in their GaN devices [7] seems to be still an unsolved problem in edge-emitting lasers (EELs). These difficulties might be resolved in nitride vertical-cavity surface-emitting lasers (VCSELs) due to the relatively small volumes of their active regions [8]. Also, the serious difficulties in manufacturing smooth highly-reflective mirrors of EELs may be relatively easy to overcome in VCSELs with semiconducting distributed Bragg reflectors (DBRs).…”

Section: Introductionmentioning

confidence: 99%

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Threshold currents of nitride vertical-cavity surface-emitting lasers with various active regions

Makowiak

Nakwaski

1998

MRS Internet j. nitride semicond. res.

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A detailed threshold analysis of room-temperature pulsed operation of GaN/AlGaN/AlN verticalcavity surface-emitting lasers (VCSELs) is carried out. The model takes advantage of the latest results concerning gain in active regions, material absorption in the cladding layers, as well as cavity diffraction and scattering losses. The simulation showed that although VCSELs with single (S) or multiple (M) quantum-well (QW) active regions exhibit lower threshold currents, they are much more sensitive to any increase in optical losses than their bulk counterparts. In particular, decreasing the active region radius of gain-guided QW VCSELs below 5 µ m (which increases diffraction losses) or increasing dislocation densities (which, in turn, raises scattering losses) gives an enormous rise to their threshold currents. Therefore small-size GaN VCSELs should have an index-guided structure. In the case of MQW VCSELs, the optimal number of quantum wells strongly depends on the reflectivities of resonator mirrors. According to our study, MQW GaN lasers usually require noticeably lower threshold currents compared to SQW lasers. The optimal number of QW active layers is lower in laser structures exhibiting lower optical losses. Although the best result occurred for an active region thickness of 4 nm, threshold currents for the various sizes differ insignificantly.

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“…Another for111 of synchronked activity in neural popillations is the widespread periodic oscillations seen in visual cortex neurons, which has been suggested to subserve a binding function (9), a suggestion potentially applicable to coordination of motor responses (14, 15). Another approach uses the "gravity" method to identify groups of neurons that tend to fire in synchrony: If n neurons are located in ndinlensiollal space, and their spikes are endowed with a transient "charge," those cells that fire synchronously tend to be attracted and form identifiable clusters (6).…”

mentioning

confidence: 99%

Longer Life for the Blue Laser

Fasol¹

1997

Science

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also change the efficacy of synaptic connections between the synchroni?ed cells (9). Riehle et al. detected the increased synchrony by comparing the number of observed coincident spikes (red bars) with the number expected by chance, based o n a running estimate of rates over a longer interval (blue bar). This running comparisoll can identify exceptional synchronizations whenever they occur. Interestingly, these occurred at times when the monkey expected a possible cue, as well as when h e made a motor response. Thus, synchronization and rate coding can occur separately or together (8, 9 , 12, 14, 15).Several other approaches can detect coherent activity in neural populations at mil-lisecol~d resolution. Standard cross-correlations between simultaneously recorded neurons commonly reveal synchronous activity, and time-dependent cross-correlation measures (1 l ) have revealed that synchronous firing can be rapidly modulated with hehavior, even without changes in firing rates (1 2).Other studies have found evidence for precisely timed patterns occurring among neural groups in a bella\~ioral situation (5). Simulations have slloaln that such synchrony can he preserved in chains of neurons with realistic synaptic connections ( 13). Another for111 of synchronked activity in neural popillations is the widespread periodic oscillations seen in visual cortex neurons, which has been suggested to subserve a binding function (9), a suggestion potentially applicable to coordination of motor responses (14, 15). Another approach uses the "gravity" method to identify groups of neurons that tend to fire in synchrony: If n neurons are located in ndinlensiollal space, and their spikes are endowed with a transient "charge," those cells that fire synchronously tend to be attracted and form identifiable clusters (6).Although all of these algorithms can detect the existence of precise tenlporal structure in neural activity, this does not yet establish their function as a temporal code. W h a t is needed first is some demonstration that synchronization occurs reliably under particular behavioral conditions. T h e accumulating evidence is suggesti.~re (5-9, 12, 14) hut still leaves the exact function unproven. Establishing the fi~nctional mechanism inay not he a matter of finding tighter correlations with behavioral events; for example, holographic lnechanislns code distributed inforlnation in terms of phase relations rather than literal representations (2). Skeptics can still argue that tlle telnporal events revealed by these methods are epiphenomena or products of tlle statistical models, and that anything telnporal coding can do, population rate coding can do as well (16). Moreover, there are open questions abililt how temporal codes are established and how they interact with rate coding (8, 15). These issues can now be investigated with the tools at hand: Multiunit recordil~gs can be analyed with these algorithms, and the detected events can be related to behavior. Neural netalork sitnulations call also help to demonstrate how the pu...

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A Perspective on the GaN Injection Laser

Abstract: This short paper is a brief review of the problems to be overcome for making an injection laser using a new semiconductor that promises to revolutionize the information storage industry.

Cited by 13 publications

References 7 publications

Epitaxial Growth and Structural Characterization of Single Crystalline ZnGeN₂

Epitaxial Growth and Structural Characterization of Single Crystalline ZnGeN₂

Threshold currents of nitride vertical-cavity surface-emitting lasers with various active regions

Longer Life for the Blue Laser

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A Perspective on the GaN Injection Laser

Abstract: This short paper is a brief review of the problems to be overcome for making an injection laser using a new semiconductor that promises to revolutionize the information storage industry.

Cited by 13 publications

References 7 publications

Epitaxial Growth and Structural Characterization of Single Crystalline ZnGeN2

Epitaxial Growth and Structural Characterization of Single Crystalline ZnGeN2

Threshold currents of nitride vertical-cavity surface-emitting lasers with various active regions

Longer Life for the Blue Laser

Contact Info

Product

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Epitaxial Growth and Structural Characterization of Single Crystalline ZnGeN₂

Epitaxial Growth and Structural Characterization of Single Crystalline ZnGeN₂