The band-gap bowing of AlxGa1−xN alloys

Lee, S. R.; Wright, A. F.; Crawford, Mary H.; Petersen, G. A.; Han, Jung; Biefeld, R. M.

doi:10.1063/1.123339

Cited by 174 publications

(94 citation statements)

References 32 publications

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“…Both LDA and sX-LDA bowing parameters are quite small and are within the experimentally measured range of 0.6 -1.0 eV. [19][20][21] Although the experimental discrepancy in the measured bowing parameter prevents us from making a more precise comparison, we can conclude that the calculated sX-LDA and LDA bowing parameters are similar and that they are both close to experiment. From the similarity of the sX-LDA and LDA results we infer that there are no serious consequences due to the band gap error of LDA in the bowing parameter calculations of these systems and also that sX-LDA can be reliably applied to this alloy system.…”

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confidence: 52%

Electronic structure of zinc-blendeAlxGa1−xN: Screened-exchange study

Lee

Wang

2006

Phys. Rev. B

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We present a first principle investigation of the electronic structure and the band gap bowing parameter of zinc-blende AlxGa1−xN using both local density approximation and screened-exchange density functional method. The calculated sX-LDA band gaps for GaN and AlN are 95% and 90% of the experimentally observed values, respectively, while LDA underestimates the gaps to 62% and 70%. In contrast to the gap itself, the band gap bowing parameter is found to be very similar in sX-LDA and LDA. Because of the difference in the conduction band structure, the direct to indirect band gap crossover is predicted to occur at different Al concentration.PACS numbers: 71.15. Mb, 71.55.Eq The group-III nitrides have long been studied for photoelectronic applications, such as ultraviolet 1 /blue 2 /green 3 light-emitting diodes and lasers. The control of emitted light in wide range frequency is possible by harnessing the large band gap differences of parent compounds through alloy fabrication. Therefore, understanding the band gap behavior of disordered alloys is valuable for designing materials with desirable properties. There have been many theoretical works for the band gap dependence on the alloy concentrations for various semiconductor alloys. Most of such previous studies were carried out using local density approximation (LDA) of the density functional theory. While LDA is reliable in calculating the atomic relaxation and formation energies of the semiconductor alloys, the calculation of their band gaps is hindered by its intrinsic errors in describing the excited states. There is no clear understanding of whether the LDA band gap errors in pure bulk crystals will cause significant errors in the band gap behavior in the alloy, especially for quantities such as the bowing parameters.While the LDA method has severely underestimated the band gap of pure III-nitrides, 4,5 the screenedexchange density functional method (sX-LDA) has been successful in many III-V semiconductors.6,7 Implemented using a Thomas-Fermi screening scheme, sX-LDA improves the LDA band gap similar to that of many-body GW calculations and also yields the ground state structure as good as LDA. Although the sX-LDA method has been systematically studied for simple II-V, III-V, IV-IV semiconductor compounds, the calculations for more complicated systems like vacancy, surface and alloys are relatively scarce. This is partly because the sX-LDA calculation, while computationally cheaper than the GW method, is still much more expensive than the LDA calculation. In the current work we test the applicability of sX-LDA for semiconductor alloy systems by comparing its results with experimental measurements and available GW calculations. We choose the Al x Ga 1−x N alloy due to the intense recent interest on these systems for potential wide gap device applications. We study Al x Ga 1−x N alloys in zinc-blende structure, and focus on the band gap bowing and the crossover of direct and indirect band gap.The calculations were carried out using a planewave basis with Tr...

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confidence: 52%

Electronic structure of zinc-blendeAlxGa1−xN: Screened-exchange study

Lee

Wang

2006

Phys. Rev. B

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“…A wide spectrum of bandgap bowing parameters has been obtained for ternary nitride alloys due to differences in growth and measurement conditions [9,10]. For unstrained layers with low mole fraction of the alloy element (x < 0.2), we employ the following roomtemperature relations for the direct bandgap [ eV]: E g ðIn x Ga 1Àx NÞ ¼ 1:89x þ 3:42ð1 À xÞ À 3:8xð1 À xÞ ð1Þ E g ðAl x Ga 1Àx NÞ ¼ 6:28x þ 3:42ð1 À xÞ À 1:3xð1 À xÞ ð2Þ…”

Section: Laser Model and Materials Parametersmentioning

confidence: 99%

Physics of high-power InGaN/GaN lasers

Piprek

Nakamura

2002

IEE Proceedings - Optoelectronics

159

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The authors analyse the performance and device physics of nitride laser diodes that exhibit the highest room-temperature continuous-wave output power. The analysis is based on advanced laser simulation. The laser model self-consistently combines band structure and freecarrier gain calculations with two-dimensional simulations of wave guiding, carrier transport and heat flux. Material parameters used in the model are carefully evaluated. Excellent agreement between simulations and measurements is achieved. The maximum output power is limited by electron leakage into the p-doped ridge. Leakage escalation is caused by strong self-heating, gain reduction and elevated carrier density within the quantum wells. Built-in polarisation fields are found to be effectively screened at high-power operation. Improved heat-sinking is predicted to allow for a significant increase of the maximum output power.

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“…8,9 Al 1−x Ga x N and Al 1−x In x N are well suited materials as photodetectors in the ultraviolet ͑UV͒ spectrum. 10 Many experimental and theoretical studies have been performed on the wurtzite structure of these ternary alloys, [11][12][13] but not much work has been done on the zinc-blende phase, since its successful growth. [14][15][16] The investigation of zinc-blende structure of these materials is more important than wurtzite structure due to its large optical gain and lower threshold current density.…”

Section: Introductionmentioning

confidence: 99%

Ab initio study of the bandgap engineering of Al1−xGaxN for optoelectronic applications

Amin¹,

Ahmad²,

Maqbool³

et al. 2011

Journal of Applied Physics

172

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A theoretical study of Al 1−x Ga x N, based on the full-potential linearized augmented plane wave method, is used to investigate the variations in the bandgap, optical properties, and nonlinear behavior of the compound with the change in the Ga concentration. It is found that the bandgap decreases with the increase in Ga. A maximum value of 5.50 eV is determined for the bandgap of pure AlN, which reaches a minimum value of 3.0 eV when Al is completely replaced by Ga. The static index of refraction and dielectric constant decreases with the increase in the bandgap of the material, assigning a high index of refraction to pure GaN when compared to pure AlN. The refractive index drops below 1 for higher energy photons, larger than 14 eV. The group velocity of these photons is larger than the vacuum velocity of light. This astonishing result shows that at higher energies the optical properties of the material shifts from linear to nonlinear. Furthermore, frequency dependent reflectivity and absorption coefficients show that peak values of the absorption coefficient and reflectivity shift toward lower energy in the ultraviolet ͑UV͒ spectrum with the increase in Ga concentration. This comprehensive theoretical study of the optoelectronic properties predicts that the material can be effectively used in the optical devices working in the visible and UV spectrum.

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The band-gap bowing of AlxGa1−xN alloys

Cited by 174 publications

References 32 publications

Electronic structure of zinc-blendeAlxGa1−xN: Screened-exchange study

Electronic structure of zinc-blendeAlxGa1−xN: Screened-exchange study

Physics of high-power InGaN/GaN lasers

Ab initio study of the bandgap engineering of Al1−xGaxN for optoelectronic applications

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