GaN-based VCSELs: analysis of internal device physics and performance limitations

Piprek, Joachim; Li, Simon

doi:10.1117/12.840515

Cited by 3 publications

(3 citation statements)

References 13 publications

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“…where γ is the power gain (negative for loss) per unit length in the material, E ⇄ 0 and H ⇄ 0 are constants, ϕ H is the phase lag between the electric and magnetic field that occurs in gainy/lossy materials, and ∆ϕ is the phase difference between right and left propagating electric fields at z = 0. By inserting (8) into (7) and carrying out the time average one obtains the desired net flux of power (net intensity) in the z-direction atz = 0 S =ẑ 1 2 {E → 0 H → 0 cos ϕ H + E ← 0 H ← 0 cos ϕ H + E → 0 H ← 0 (cos ϕ H cos ∆ϕ − sin ϕ H sin ∆ϕ)+ E ← 0 H → 0 (cos ϕ H cos ∆ϕ + sin ϕ H sin ∆ϕ)≡ẑ S .…”

Section: Discussionmentioning

confidence: 99%

“…Numerical simulations of GaN-based VCSELs are complicated because of the detailed structures and a remaining uncertainty regarding both values for several material parameters as well as the importance of phenomena such as the strong self-polarization in GaN-based materials. In [7] two experimentally reported GaN-based VCSELs, including the first roomtemperature emitting device from Nichia Corporation [8], were numerically simulated retrospectively. These devices did not have a current aperture, and the main limitations to the performance were found to be electrical, particularly the current crowding, leading to lower threshold currents for higher order modes than for the fundamental mode.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of structurally sensitive loss in GaN-based VCSEL cavities and its effect on modal discrimination

Hashemi¹,

Bengtsson²,

Gustavsson³

et al. 2014

Opt. Express

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Lateral loss causes optical energy to leave the laser cavity in the transverse, lateral, direction, and is sometimes neglected to simplify the numerical simulations. However, in contrast to outcoupling and absorption losses, we show that the lateral loss can change drastically with only nanometer-sized changes of the cavity structure, from being virtually zero to becoming the major source of cavity loss, since the cavity becomes antiguiding. This can be explained as the opening of a channel of efficient resonant lateral leakage of optical power at a certain oblique propagation angle. A number of different realizations of current apertures and top mirror designs in GaN-based VCSEL cavities, which have been suggested for realization of microcavity lasers emitting in the blue wavelength range, are simulated. Many of these are shown to lead to unintentional antiguiding, which can more than double the threshold gain for lasing. Notably, for strong enough antiguiding the resonant lateral leakage decreases so that the threshold gain values might again be tolerable. This regime has been suggested for robust single-mode operation since earlier predictions, building on analogies with slab waveguides, hinted at a very strong suppression of higher order modes. However, our simulations indicate that for the VCSEL cavities the derived formulas grossly overestimate the modal discrimination.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of structurally sensitive loss in GaN-based VCSEL cavities and its effect on modal discrimination

Hashemi¹,

Bengtsson²,

Gustavsson³

et al. 2014

Opt. Express

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show abstract

“…This coe cient varies within the range of 20% [30] to 80% [31]. Within LED simulations that are GaN-based, a common value is 50% [32]. For the simulations showcased in this research, this coe cient retains the value of 50%.…”

Section: Parameters and Structuresmentioning

confidence: 78%

Impact of boron in ultraviolet quantum well-based light emitting diodes

Dhivyasri,

Manikandan,

Ajayan

et al. 2023

Preprint

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The ByAlxGa1-x–yN system validates promise as a suitable option for fabricating opto-electronic devices like Light-Emitting-Diodes (LEDs) & laser diodes. This study conducts a comparative analysis between two types of LEDs: one with a single quantum well (SQW) composed of AlGaN and another with BAlGaN, containing 1% boron, 22% aluminum, and a 3 nm thickness. These LEDs are designed as AlGaN-based Quantum Well (LED1) and BAlGaN-based Quantum well devices (LED2). Technology Computer-Aided Design (TCAD) Silvaco physical simulator is used to perform simulations and comparisons in terms of both optical and electrical characteristics. The simulations encompass the anode current with respect to anode voltage, luminous power and wall-plug efficiency relative to injection current, and power spectral density concerning wavelength. Remarkably, even with a mere 1% boron content within the quantum well, the LED's performance displays a 2.3% enhancement in power spectral density and a 10% boost in wall-plug efficiency.

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What is the problem with GaN-based VCSELs?

Piprek¹

2013

2013 13th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD)

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In contrast to the impressive progress of GaNbased edge-emitting lasers in recent years, III-nitride vertical-cavity surface-emitting lasers (VCSELs) still exhibit severe performance limitations. Using advanced device simulation, this presentation evaluates design and material issues with different GaN-VCSEL concepts and identifies performance limiting internal mechanisms.Similar to widely used GaAs-based vertical-cavity surface-emitting lasers (VCSELs), GaN-based VCSELs are expected to show various advantages over their edge-emitting counterparts, including lower manufacturing costs, circular and low-divergence output beam, single longitudinal mode emission, low threshold, high-speed modulation, high-density two-dimensional arrays, wafer-level testing, and longer lifetime. Potential applications of GaN-VCSELs include laser display, solid-state lighting, high-density optical data storage, high-resolution printing, low-cost optical communication, and bio-sampling. However, in contrast to the success of GaNbased edge-emitting lasers in recent years, GaN-VCSELs still face significant challenges. 1 One of the key material problems is the poor quality of AlGaN/GaN distributed Bragg reflectors (DBRs) due to the large lattice mismatch of GaN and AlN. A possible solution is the use of one or two dielectric DBRs. However, the employment of dielectric DBRs on both sides of the VCSEL cavity requires the removal of the majority of the GaN substrate combined with a precise control of the remaining cavity length. 2 This presentation evaluates different current-injected GaN-VCSEL design concepts that show room-temperature (RT) continuous-wave (CW) operation. The design of VCSELs in general is very demanding and numerical simulation is often used for design optimization. 3 We here employ the laser simulation software PICS3D 4 that self-consistently combines the computation of carrier transport, energy band structure, optical gain, optical modes, and self-heating. The transport model includes drift and diffusion of electrons and holes, Fermi statistics, built-in polarization and thermionic emission at hetero-interfaces, as well as photon emission, Auger recombination, and defect-related Shockley-Read-Hall (SRH) recombination. For the quantum wells, Schrödinger and Poisson equations are solved iteratively to account for the quantum-confined Stark effect (QCSE) caused by nitride polarization. Stimulated and spontaneous emission of photons within the quantum well is calculated self-consistently based on the wurtzite energy band structure. More details on model and parameters are given elsewhere. 5 A similar model was previously employed in the analysis of high-power GaN-based edge-emitting lasers, resulting in very good agreement with measurements. 6 Fig. 1: Vertical profile of refractive index and standing optical wave in the center of the VCSEL from Ref. 9.The first continuous-wave (CW) operation of a current-injected GaN-VCSEL was demonstrated in 2008 at a low temperature of 77K utilizing an n-side AlN/GaN DBR with superlattice i...

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GaN-based VCSELs: analysis of internal device physics and performance limitations

Cited by 3 publications

References 13 publications

Analysis of structurally sensitive loss in GaN-based VCSEL cavities and its effect on modal discrimination

Analysis of structurally sensitive loss in GaN-based VCSEL cavities and its effect on modal discrimination

Impact of boron in ultraviolet quantum well-based light emitting diodes

What is the problem with GaN-based VCSELs?

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