Dominant role of the piezoelectric field in the pressure behavior of InGaN/GaN quantum wells

Vaschenko, G.; Patel, D.; Menoni, C.S.; Keller, S.; Mishra, U. K.; DenBaars, Steven P.

doi:10.1063/1.1343479

Cited by 38 publications

(45 citation statements)

References 13 publications

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“…The experimental results just described are quite similar to the observations made in our previous work on In x Ga 1Ϫx N/GaN QWs, 6 and provide additional evidence on the nonlinear behavior of the polarization in the III-V nitrides. As in the case of In x Ga 1Ϫx N/GaN QWs, the small values of dE/dp and their well width dependence result from an increase of the built-in electric field with pressure.…”

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confidence: 80%

“…In agreement with this prediction, we demonstrated experimentally that the piezoelectric coefficients in In x Ga 1Ϫx N/GaN QWs significantly depend on the strain. 6 We have also suggested that volumetric as well as volume conserving components of strain affect these coefficients. Recently, Bernardini and Fiorentini investigated theoretically the effects of strain and composition on macroscopic polarization in III-V nitrides, and showed that in addition to the nonlinearity in the piezoelectric component of polarization, the spontaneous polarization is also nonlinear with respect to composition.…”

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confidence: 99%

“…The decay time increase is due to the increased spatial charge separation in the wells by the electric field leading to the reduction in the electron-hole wave function overlap. 6 In the following, we provide an analysis of the experimental data aimed at evaluating the magnitude of the built-in electric field at different pressures. Since the field magnitude depends on the sample geometry and distribution of free charges, we concentrate on determining the polarization difference P w Ϫ P b instead, which defines the electric field F w in the wells as 9…”

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confidence: 99%

“…To apply pressure to the samples, they were cut and polished to a 70ϫ70ϫ30 m 3 size, and loaded into a diamond anvil cell filled with liquid argon as a pressure transmitting media. 6 All PL measurements were performed at 35 K. Figure 1 shows a typical pressure dependence of the PL peak energies in the sample with Al 0.5 Ga 0.5 N barriers. The pressure coefficients (dE/dp) of the QW PL peak are much smaller than that of GaN ͑ϳ39 meV/GPa͒ and they decrease with increasing well width from 26.2 meV/GPa in the 1.8 nm well to only 2.9 meV/GPa in the 4.9 nm well.…”

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Nonlinear macroscopic polarization in GaN/AlxGa1−xN quantum wells

Vaschenko

Patel

Menoni

et al. 2002

Applied Physics Letters

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We present experimental evidence of the nonlinear behavior of the macroscopic polarization in GaN/Al x Ga 1Ϫx N quantum wells. This behavior is revealed by determining the barrier-well polarization difference as a function of applied hydrostatic pressure. The polarization difference and corresponding built-in electric field in the wells increase with applied pressure at a much higher rate than expected from the linear model of polarization. This result, universally observed in the quantum well structures with different AlN mole fraction in the barriers, is explained by the nonlinear dependence of the piezoelectric polarization in GaN and AlN on the strain generated by pressure. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1483906͔ Polarization-induced electric fields have a detrimental effect on the electrical and optical characteristics of GaNbased quantum well ͑QW͒ devices with wurtzite lattice configuration. In short-wavelength laser diodes, these fields increase the threshold current and redshift the emission wavelength. 1 In emerging long-wavelength structures utilizing intersubband transitions, the fields increase the intersubband relaxation time and reduce the effective barrier height. 2 To utilize the effects of polarization-induced fields in device design in a controllable way, one needs to be able to quantify these fields with good precision. Although significant advances were made in the last few years in the theory of macroscopic polarization in III-V nitrides, 3 some issues are still awaiting clarification. One of them is the effect of alloy composition and strain on the polarization. Original investigations assumed that piezoelectric coefficients and spontaneous polarization in nitrides are insensitive to these parameters. 1,4 However, Shimada et al. 5 predicted theoretically that the piezoelectric coefficients of GaN, AlN, and BN strongly depend on volume conserving strain. In agreement with this prediction, we demonstrated experimentally that the piezoelectric coefficients in In x Ga 1Ϫx N/GaN QWs significantly depend on the strain. 6 We have also suggested that volumetric as well as volume conserving components of strain affect these coefficients. Recently, Bernardini and Fiorentini investigated theoretically the effects of strain and composition on macroscopic polarization in III-V nitrides, and showed that in addition to the nonlinearity in the piezoelectric component of polarization, the spontaneous polarization is also nonlinear with respect to composition. 7 In this work, we provide experimental evidence of the nonlinear polarization response of GaN/Al x Ga 1Ϫx N quantum wells to strain. To modify the strain in the wells and in the barriers, we apply hydrostatic pressure to the samples. The strain generated by pressure increases the built-in electric field in the wells, which is manifested in a pressure dependent Stark shift of the photoluminescence ͑PL͒ emission peak. The values of well-barrier polarization difference ( P w Ϫ P b ) and corresponding electric field are obtained fro...

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confidence: 80%

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confidence: 99%

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confidence: 99%

mentioning

confidence: 99%

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Nonlinear macroscopic polarization in GaN/AlxGa1−xN quantum wells

Vaschenko

Patel

Menoni

et al. 2002

Applied Physics Letters

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“…Also in the case of InGaN/GaN quantum wells similar behaviour was observed. [14][15][16] Generally the increase of built-in electric field is explained by pressure induced increase of strain which leads to an increase of piezoelectric component of built-in electric field. Actually the experimental observations are explained by more sophisticated theories including nonlinear piezoelectric constants, pressure-induced changes of the exciton binding energy and nonlinear elastic stiffness coefficients.…”

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Pressure induced increase of the exciton phonon interaction in ZnO/(ZnMg)O quantum wells

et al. 2016

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It is a well-established experimental fact that exciton-phonon coupling is very efficient in ZnO. The intensities of the phonon-replicas in ZnO/(ZnMg)O quantum structures strongly depend on the internal electric field. We performed high-pressure measurements on the single ZnO/(ZnMg)O quantum well. We observed a strong increase of the intensity of the phonon-replicas relative to the zero phonon line. In our opinion this effect is related to pressure induced increase of the strain in quantum structure. As a consequence, an increase of the piezoelectric component of the electric field is observed which leads to an increase of the intensity of the phonon-replicas.

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Pressure Dependence of Piezoelectric Field in InGaN/GaN Quantum Wells

Vaschenko

Patel

Menoni

et al. 2001

phys. stat. sol. (b)

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In this work we use the well width dependence of the quantum confined Stark effect to determine the variation of the built-in piezoelectric field in InGaN/GaN quantum wells with applied hydrostatic pressure. We find that the field increases from 1.4 MV/cm at atmospheric pressure to 2.6 MV/cm at 8.7 GPa. An analysis of the strain generated by the pressure suggests that the increase in the field is due to a dramatic dependence of the piezoelectric constants of GaN and InGaN on strain.Built-in piezoelectric fields (F pz ) play an important role in devices based on InGaN/ GaN quantum wells (QWs) with wurtzite lattice configuration. To quantify the effect of these fields one needs to know the exact geometry of the device, the strain state, and the piezoelectric constants of the materials forming the quantum wells. While the first two characteristics can be determined quite precisely, the latter one is subject to a significant uncertainty. The experimentally defined values of the piezoelectric constant e 33 of GaN range from 0.43 C/m 2 [1] to 1.12 C/m 2 [2], with the theoretically predicted values of 0.63-0.73 C/m 2 [3,4]. For InN the piezoelectric constants are not determined experimentally yet. The predicted value of e 33 in InN is 0.81 C/m 2 [5]. To even worsen this uncertainty, the piezoelectric constants of InGaN quantum wells are commonly linearly interpolated from the values of the piezoelectric constants of the binaries forming the alloy [6,7]. This approach neglects the effect of the microscopic strains associated with alloy mixing and the macroscopic strain generated by the lattice mismatch between GaN and InGaN. In this work we show that piezoelectric constants of GaN and InGaN have a dramatic dependence on the macroscopic strain. To reveal this dependence we apply hydrostatic pressure to the QW structures to modify the strain state in the wells and in the barriers. This results in a strikingly large increase of the F pz . An analysis of the strain state shows that the increase of the F pz arises from the nonlinear piezoelectric effect [3,8], i.e. the strain dependence of the piezoelectric constants.The QW structures studied in this work were grown by metal organic chemical vapour deposition on (0001) sapphire substrates. Each structure has four identical quantum wells with indium composition of~15% and GaN barriers. The barriers are 12.5 nm wide and the well widths in the three different samples are 2.5, 3.1, and 3.8 nm respectively. The QW regions are grown on 3.5 mm GaN layers.

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Dominant role of the piezoelectric field in the pressure behavior of InGaN/GaN quantum wells

Cited by 38 publications

References 13 publications

Nonlinear macroscopic polarization in GaN/AlxGa1−xN quantum wells

Nonlinear macroscopic polarization in GaN/AlxGa1−xN quantum wells

Pressure induced increase of the exciton phonon interaction in ZnO/(ZnMg)O quantum wells

Pressure Dependence of Piezoelectric Field in InGaN/GaN Quantum Wells

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