Valence-band discontinuities of wurtzite GaN, AlN, and InN heterojunctions measured by x-ray photoemission spectroscopy

Martin, G.; Botchkarev, A.; Rockett, Angus; Morkoç, H.

doi:10.1063/1.116177

Cited by 687 publications

(310 citation statements)

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“…They then go on to match the experimentally observed results with an internal field of E int = 1.2 MV cm −1 , which compares to a theoretical value of E int = 2.5 MV cm −1 obtained by interpolating the piezoelectric and elastic constants from the binary values. 8 Recalculating these results using the p-i-n junction model, we get values of 49 and 1.5 nm for the depletion widths ͑corresponding to Ϫ10 and 3 V, respectively͒ and the flat band voltage of Ϫ14 V corresponds to a internal field of E int = 2.6 MV cm −1 , which is within 5% of the theoretical result.…”

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confidence: 53%

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Determination of the piezoelectric field in InGaN quantum wells

Brown

Pope

Smowton

et al. 2005

Applied Physics Letters

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In many studies, the value of the experimentally determined internal piezoelectric field has been reported to be significantly smaller than theoretical values. We believe this is due to an inappropriate approximation for the electric field within the depletion region, which is used in the analysis of experimental data, and we propose an alternative method. Using this alternative, we have measured the strength of the internal field of InGaN p-i-n structures, using reverse bias photocurrent absorption spectroscopy and by fitting the bias dependent peak energy using microscopic theory based on the screened Hartree-Fock approximation. The results agree with those using material constants interpolated from binary values. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1896446͔The internal field in GaN based quantum wells plays an important role in the operation of nitride-based light emitting diodes and lasers, affecting the emission wavelength, 1 the oscillator strength, 2 and the recombination lifetime, 3 hence an accurate value of the internal field is essential in understanding the properties of these devices. The internal field skews and breaks the symmetry of the well, causing spatial separation of the electron and hole wave functions and hence reduces the electron-hole overlap function. Reported values of the internal field 4,5 for the same nominal indium content vary by more than a factor of two, which is far greater than the expected error due to unintended variations in the indium content. Also there are large reported differences between theoretical and experimental results. 6 The majority of approaches to determine the internal field, have relied upon counteracting the quantum-confined Stark effect with an externally applied reverse bias and measuring properties of the quantum well as a function of this applied reverse bias. The reverse bias acts to oppose the internal field reducing the effect of the induced quantum confined Stark effect. At low bias, the well is skewed due to the internal field. At a critical bias, the contributions from the applied bias and the internal field are equal and opposite. In this case, the overlap of electron and hole wave functions and the ground state electron to heavy hole transition energy are maximized.The value of the externally applied bias to achieve flat band ͑"square-up" the quantum well͒ can then be used to obtain the internal field. The net internal field E in the well ͑E = 0 when the well is square͒ is related to the applied bias V using: 4where E int , L w , N, 0 , d d , and d u are the internal field, the quantum well width, the number of quantum wells, the built-in potential and the depletion and intrinsic widths, respectively. The width of the intrinsic region d u is given by the sum of the multiple well and barrier widths. The internal field E int , is the sum of the fields due to the piezoelectric effect and the spontaneous polarization. The first term of Eq. ͑1͒ is the background field written as the total voltage drop divided by the distance, over ...

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“…This compares with 1.8 MV cm −1 obtained using the calculation when the material constants are obtained by interpolating the binary values. 8 A comparison of the experimental and calculated results for the amplitude of the measured peak absorption is shown in Fig. 4 and shows there is good agreement at high values of bias but poor agreement at low bias.…”

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confidence: 99%

Determination of the piezoelectric field in InGaN quantum wells

Brown

Pope

Smowton

et al. 2005

Applied Physics Letters

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“…Using c M =377 GPa, ci 2 =160 GPa, c 13 =114 GPa, c 33 =209 GPa [12], and s r =9.5 [6], we obtain d3i=-1.4xl0" 10 cm/V. Our value of d 3 i is almost the average value between a value of -0.9xl0" 10 cm/V obtained by Im et al [6] and -1.7x10"'° cm/V by Martin et al [13]. This value is also comparable with d33=2.0xl0" 10 cm/V as recently measured by Muensit et al using a laser interferometer [14].…”

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confidence: 61%

Piezoelectric effects on the optical properties of GaN/AlxGa1−xN multiple quantum wells

Kim

Lin

Jiang

et al. 1998

Applied Physics Letters

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105

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Abstract:Piezoelectric effects on the optical properties of GaN/AlGaN multiple quantum wells (MQWs) have been investigated by picosecond time-resolved photoluminescence (PL) measurements. For MQWs with well thickness 30 A and 40 A, the excitonic transition peak positions at 10 K in continuous wave (cw) spectra are redshifted with respect to the GaN epilayer by 17 meV and 57 meV, respectively. The time-resolved PL spectra of the 30 A and 40 A well MQWs reveal that the excitonic transition is in fact blueshifted at early delay times due to quantum confinement of carriers. The spectral peak position shifts toward lower energies as the delay time increases and becomes redshifted at longer delay times. We have demonstrated that the results described above is due to the presence of the piezoelectric field in the GaN wells of GaN/AlGaN MQWs subject to elastic strain together with screening of the photoexcited carriers. By comparing experimental and calculation results, we conclude that the piezoelectric field strength in GaN/Alo.isGao.8sN MQWs has a lower limit value of about 560 kV/cm. The electron and hole wave function distributions have also been obtained. The implication of our findings on the practical applications of GaN based optoelectronic devices is also discussed.

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“…The VB offset between GaN and InN has been measured in a number of studies. 4,[21][22][23][24][25][26][27][28] The most recent experimental study reported an offset of 0.58 ± 0.08 eV. 28 However, accurately measuring the offset is very difficult as seen from the wide spread (between 0.6 and 1.1 eV) of the reported experimental values.…”

Section: Alloys Ofmentioning

confidence: 99%

Hybrid functional investigations of band gaps and band alignments for AlN, GaN, InN, and InGaN

Moses

Miao

Yan

et al. 2011

The Journal of Chemical Physics

284

231

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Band gaps and band alignments for AlN, GaN, InN, and InGaN alloys are investigated using density functional theory with the with the Heyd-Scuseria-Ernzerhof {HSE06 [J. Heyd, G. E. Scuseria, and M. Ernzerhof, J. Chem. Phys. 134, 8207 (2003); 124, 219906 (2006)]} XC functional. The band gap of InGaN alloys as a function of In content is calculated and a strong bowing at low In content is found, described by bowing parameters 2.29 eV at 6.25% and 1.79 eV at 12.5%, indicating the band gap cannot be described by a single composition-independent bowing parameter. Valence-band maxima (VBM) and conduction-band minima (CBM) are aligned by combining bulk calculations with surface calculations for nonpolar surfaces. The influence of surface termination [(1100) mplane or (1120) a-plane] is thoroughly investigated. We find that for the relaxed surfaces of the binary nitrides the difference in electron affinities between m-and a-plane is less than 0.1 eV. The absolute electron affinities are found to strongly depend on the choice of XC functional. However, we find that relative alignments are less sensitive to the choice of XC functional. In particular, we find that relative alignments may be calculated based on Perdew-Becke-Ernzerhof [J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 134, 3865 (1996)] surface calculations with the HSE06 lattice parameters. For InGaN we find that the VBM is a linear function of In content and that the majority of the band-gap bowing is located in the CBM. Based on the calculated electron affinities we predict that InGaN will be suited for water splitting up to 50% In content.

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Valence-band discontinuities of wurtzite GaN, AlN, and InN heterojunctions measured by x-ray photoemission spectroscopy

Cited by 687 publications

References 1 publication

Determination of the piezoelectric field in InGaN quantum wells

Determination of the piezoelectric field in InGaN quantum wells

Piezoelectric effects on the optical properties of GaN/AlxGa1−xN multiple quantum wells

Hybrid functional investigations of band gaps and band alignments for AlN, GaN, InN, and InGaN

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