Free-carrier screening of polarization fields in wurtzite GaN/InGaN laser structures

Sala, Fabio Della; Carlo, Aldo Di; Lugli, Paolo; Bernardini, Fabio; Fiorentini, Vincenzo; Scholz, Reinhard; Jancu, Jean–Marc

doi:10.1063/1.123727

Cited by 265 publications

(74 citation statements)

References 20 publications

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“…Similar considerations hold for the densities of bipolar photogenerated carriers in the high density optical pumping experiments. This is in agreement with recent calculations in the literature [9] showing that the large polarization fields cannot be screened under injection of bipolar carriers up to the expected lasing threshold density. Completely two-dimensional polarization charges and the associated fields therefore significantly supersede effects achievable by modulation doping.…”

Section: Resultssupporting

confidence: 93%

Discrete Stark-Like Ladder in Piezoelectric GaInN/GaN Quantum Wells

Wetzel¹,

Kasumi

Detchprohm

et al. 1999

phys. stat. sol. (b)

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The optical properties and their relation to the electronic bandstructure in Si-doped GaInN/GaN multiple quantum well structures typical for near UV laser diode devices are investigated in photoluminescence, photoluminescence excitation and photoreflection spectroscopies. A set of four evenly spaced levels N 0 Á Á Á N 3 is identified covering the spectral range from the lowest luminescence band (N 3 ) to the GaN barrier energy (N 0 ). The splitting of N 3 and N 2 appears as a discrete splitting rather than a continuous localization process. The level splitting is well described by a Stark-like ladder defined by the multi interface bandoffset DE FeL z across the piezoelectric GaN/GaInN/GaN structure.

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Section: Resultssupporting

confidence: 93%

Discrete Stark-Like Ladder in Piezoelectric GaInN/GaN Quantum Wells

Wetzel¹,

Kasumi

Detchprohm

et al. 1999

phys. stat. sol. (b)

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“…When increasing the excitation power density, in addition to the increase in IQE, the GaInN/GaN QWs peak emission wavelength is blue-shifted due to the screening piezoelectric field by free-carriers. 31,32 For the reference sample the emission peak around 528 nm is red-shifted to 537 nm when the excitation power is decreased to 1 mW/cm 2 . Such a red-shift with decreasing excitation power is also present for samples A-C. For sample A this implies an emission peak shift towards the LSP resonance.…”

Section: Excitation Power Density Dependent Iqementioning

confidence: 99%

Internal quantum efficiency enhancement of GaInN/GaN quantum-well structures using Ag nanoparticles

et al. 2015

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We report internal quantum efficiency enhancement of thin p-GaN green quantum-well structure using self-assembled Ag nanoparticles. Temperature dependent photoluminescence measurements are conducted to determine the internal quantum efficiency. The impact of excitation power density on the enhancement factor is investigated. We obtain an internal quantum efficiency enhancement by a factor of 2.3 at 756 W/cm2, and a factor of 8.1 at 1 W/cm2. A Purcell enhancement up to a factor of 26 is estimated by fitting the experimental results to a theoretical model for the efficiency enhancement factor.

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“…[96], in fact depends on injection and particulars of the active-region [97]. The B ef f coefficient initially increases with injection and then tends to saturate at high injection levels as the flat band condition is approached [95]. larger B ef f coefficients, respectively, at 100 A/cm 2 .…”

Section: Injection-dependent Radiative Recombination Coefficient (B) mentioning

confidence: 99%

“…Discussed next are the effects of the active region design and the resulting polarization-induced field [95] on the overlap integral and the associated spontaneous recombination rates in InGaN structures with QWs and DH at different injection levels. Figure 19 represents the simulated bimolecular recombination coefficients, B ef f , derived from the transition matrix element and thus the simulated squared overlap integrals of the electron and hole wavefunctions in the single and multi DH active regions.…”

Section: Injection-dependent Radiative Recombination Coefficient (B) mentioning

confidence: 99%

Saga of efficiency degradation at high injection in InGaN light emitting diodes

Avrutin¹,

Hafiz²,

Zhang³

et al. 2014

Turk J Phys

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Abstract:What has turned into highly complex and somewhat misunderstood efficiency loss mechanisms occurring in light-emitting diodes (LEDs) based on the InN-GaN material system at high injection levels are discussed. Suggestions are made as to the dominant mechanism(s) in an open forum format as well as pointing out some of the shortcomings of the methodologies used and premises forwarded. It is unequivocally known that increased junction temperature would cause a reduction in radiative power due to mainly the reduction in radiative recombination efficiency. Another obvious mechanism is the asymmetry in doping in wide bandgap semiconductors, such as GaN, wherein the hole concentration lags well behind that of electrons in the active region. Because an electron and a hole are required for radiative recombination, the radiative efficiency cannot keep up with increasing carrier injection due to progressively lagging hole population. This results in either electron escape without radiative recombination or electron accumulation, which in turn changes the internal bias of the device, manifested as reduced internal forward bias, which reduces the rate of increase in light intensity.Some of the reports ascribe the efficiency loss at high injection levels to Auger recombination (mainly through indirect and recently reportedly direct deductions) as the main and or the only source of efficiency loss by in many cases simply relying on the temperature and injection independent (not well taken) A, B, C coefficients to fit a third order polynomial to the efficiency vs. injection current. As for the direct deduction, the spectroscopic analysis of Auger kicked hot electrons as they traverse through the Γ and L bands before being emitted into the vacuum by means of cesiated surface challenges the existing theories and some experiments regarding carrier scattering and Γ -L separation. Despite just a few reports to the contrary, the bulk of the resonant optical emission experiments do not support the Auger argument as being the main cause. In parallel, there exists a body of theoretical and experimental reports for electron overflow of ballistic/quasi-ballistic electrons traversing the active region to p-GaN, escaping recombination altogether in the active region. In fact and from the get go, the LED industry ubiquitously employed, and continues to do so, an (Al,In)GaN electron-blocking layer (EBL) to prevent electron escape for improved light output that in and of itself would more than suggest that the electron escape (overflow) does indeed occur. The only adverse effect of EBL is * Correspondence: vavrutin@vcu.edu 269 AVRUTIN et al./Turk J Phys that it impedes hole injection due to the valence band offset between the p-type (Al,In)GaN EBL and p-GaN and also generates piezoelectric (if not lattice matched) and differential spontaneous polarization induced fields that pull down the conduction band edge at the interface reducing EBL's effectiveness. To at least reduce the aforementioned aggravating factors to some extent, the ele...

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Free-carrier screening of polarization fields in wurtzite GaN/InGaN laser structures

Cited by 265 publications

References 20 publications

Discrete Stark-Like Ladder in Piezoelectric GaInN/GaN Quantum Wells

Discrete Stark-Like Ladder in Piezoelectric GaInN/GaN Quantum Wells

Internal quantum efficiency enhancement of GaInN/GaN quantum-well structures using Ag nanoparticles

Saga of efficiency degradation at high injection in InGaN light emitting diodes

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