Effects of biaxial strain on exciton resonance energies of hexagonal GaN heteroepitaxial layers

Chichibu, S. F.; Shikanai, A.; Azuhata, T.; Sota, Takayuki; Kuramata, Akito; Horino, K.; Nakamura, Shuji

doi:10.1063/1.116000

Cited by 118 publications

(48 citation statements)

References 13 publications

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“…Indeed, dominant resonance structures due to A and B FEs were found in both absorption and photoreflectance spectra of 3D GaN layers, and FE emission has been found even at RT, 39,40 since the exciton binding energy, E b , is as large as 26 meV and a B is as small as 3.4 nm. 20,[39][40][41][42][43] It is also known that E b is increased in QWs 44 due to confinement of wavefunctions.…”

Section: Frameworkmentioning

confidence: 99%

Spectroscopic Studies in InGaN Quantum Wells

Chichibu

Sota

Wada

et al. 1999

MRS Internet j. nitride semicond. res.

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Cite this article as: MRS Internet J. Nitride Semicond. Res. 4S1, G2.7(1999). AbstractFundamental electronic modulations in strained wurtzite III-nitride, in particular In x Ga 1-x N, quantum wells (QWs) were treated to explore the reason why practical InGaN devices emit bright luminescences in spite of the large threading dislocation (TD) density. The emission mechanisms were shown to vary depending on the well thickness L and InN molar fraction x. The electric field across the QW plane, F, which is a sum of the fields due to spontaneous and piezoelectric polarization and the pn junction field, causes the redshift of the ground state resonance energy through the quantum confined Stark effect (QCSE). The absorption spectrum is modulated by QCSE, quantum-confined Franz-Keldysh effect (QCFK), and Franz-Keldysh (FK) effect from the barrires when, for the first approximation, potential drop across the well (F L) exceeds the valence band discontinuity, E V . Under large F L, holes are confined in the triangular potential well formed at one side of the well. This produces apparent Stokes-like shift in addition to the in-plane net Stokes shift on the absorption spectrum. The QCFK and FK further modulate the electronic structure of the wells with L greater than the three dimensional (3D) free exciton (FE) Bohr radius, a B . When F L exceeds E C , both electron (e) and hole (h) confined levels drop into the triangular potential wells at opposite sides of the wells, which reduces the wavefunction overlap. Doping of Si in the barriers partially screens the F resulting in a smaller Stokes-like shift, shorter recombination decay time, and higher emission efficiency. Finally, the use of InGaN was found to overcome the field-induced oscillator strength lowering due to the spontaneous and piezoelectric polarization. Effective in-plane localization of the QW excitons (confined excitons, or quantized excitons) in quantum disk (Q-disk) size potential minima, which are produced by nonrandom alloy potential fluctuation enhanced by the large bowing parameter and F, produces confined e-h pairs whose wavefunctions are still overlapped when L

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Section: Frameworkmentioning

confidence: 99%

Spectroscopic Studies in InGaN Quantum Wells

Chichibu

Sota

Wada

et al. 1999

MRS Internet j. nitride semicond. res.

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“…In the future, detailed investigations are needed. However, the strain generated in the GaN/Al 0.1 Ga 0.9 N system is only about 0.1% in the c-axis direction [32] so that there would be no hindrance to the realization of surface emission in a GaN/AlGaN laser with high-injection operation. Nevertheless, it may be necessary to consider reduction of the transition probability in the fabrication of the laser diode in order to achieve lowerthreshold operation.…”

Section: Strain In the Crystal And Light Emitting Characteristicsmentioning

confidence: 97%

Design and fabrication process consideration of GaN-based surface emitting lasers

Honda

Shirasawa

Mochida

et al. 1999

Electron. Comm. Jpn. Pt. II

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“…However, since the incident light was unpolarized and the thin ZnO crystal film strained by the lattice mismatch with the sapphire substrate, leading to relaxation of the selection rules, all the three transitions are revealed in the reflectance spectra, and the oscillator strength of the C exciton is found to be smaller than that of the A and B excitons. 27,28 The wellresolved, sharp resonance peaks imply an extraordinarily low damping effect, indicating a very low concentration of residual free carriers in addition to the high optical quality of the material. As the temperature increases, the peaks gradually broaden and shift to lower energies.…”

Section: Methodsmentioning

confidence: 99%

Intrinsic exciton transitions in high-quality ZnO thin films grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates

Zhang

Yao

Huang

et al. 2006

Journal of Applied Physics

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High-quality ZnO thin films have been grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. Free-exciton absorption and exciton-LO phonon absorption peaks are observed in the films at room temperature, indicating that the exciton states are stable even at room temperature. Three excitonic transitions associated with valence bands A, B, and C are clearly revealed in the reflectance spectrum measured at low temperatures. This result indicates that the ZnO thin films have a perfect wurtzite crystal structure. Biexciton emission is observed in the photoluminescence spectra at low temperatures, from which the biexciton binding energy is estimated to be 14.5 meV, in good agreement with previous results. Exciton-LO ͑Ex-LO͒ and exciton-2LO ͑Ex-2LO͒ photon emission peaks are observed at low temperature. The energy difference between the Ex-LO and Ex-2LO bands is about 72.5 meV, which coincides with previously reported values of the LO phonon energy for ZnO thin films.

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Effects of biaxial strain on exciton resonance energies of hexagonal GaN heteroepitaxial layers

Cited by 118 publications

References 13 publications

Spectroscopic Studies in InGaN Quantum Wells

Spectroscopic Studies in InGaN Quantum Wells

Design and fabrication process consideration of GaN-based surface emitting lasers

Intrinsic exciton transitions in high-quality ZnO thin films grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates

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