Optical Properties of Strained AlGaN and GaInN on GaN

Takeuchi, Tetsuya; Takeuchi, Hideo; Sota, Shigetoshi; Sakai, Hiromitsu; Amano, Hiroshi; Akasaki, Isamu

doi:10.1143/jjap.36.l177

Cited by 338 publications

(187 citation statements)

References 20 publications

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“…Samples were grown in metal organic vapor phase epitaxy (MOVPE) on (0001) sapphire substrates using low temperature deposited AlN buffer layers [24] [25]. Further details have been given in Ref.…”

Section: Methodsmentioning

confidence: 99%

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On the Bandstructure in GaInN/GaN Heterostructures - Strain, Band Gap and Piezoelectric Effect

Wetzel

Nitta

Takeuchi

et al. 1998

MRS Internet j. nitride semicond. res.

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A study of the optoelectronic properties of strained 40 nm Ga 1-x In x N layers on GaN films is presented. The fact of pseudomorphic strain leads to a new interpretation of the film composition when derived from x-ray scattering. In addition we directly confirm that strain induces huge piezoelectric fields in this uniaxial system by the observation of Franz-Keldysh oscillations in photoreflection. As a function of composition (0 < x < 0.2) and strain we derive the electronic band gap energy and the piezoelectric field strength. We interpret both in terms of effective bowing parameters and piezoelectric coefficients, respectively. From a spatially resolved micro photoluminescence at room temperature we find no evidence for spatial band gap or composition variations of more than 60 meV over the length scale from 1 to 50 µ m (x=0.187) in our material. At the same time, an observed discrepancy between photoluminescence peak energy and photoreflection band gap energy increases with x to some 160 meV. We attribute this redshift to photon assisted tunneling in the huge piezoelectric fields (Franz-Keldysh effect).

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Section: Methodsmentioning

confidence: 99%

“…Ternary layers at a thickness of 40 nm were grown pseudomorphically onto 2 µ m GaN. Pseudomorphic growth and x were determined from high resolution x-ray diffraction of a and c lattice constants [25]. PR at room temperature was performed using a Xe-arc lamp source in near-toperpendicular reflection.…”

Section: Methodsmentioning

confidence: 99%

On the Bandstructure in GaInN/GaN Heterostructures - Strain, Band Gap and Piezoelectric Effect

Wetzel

Nitta

Takeuchi

et al. 1998

MRS Internet j. nitride semicond. res.

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“…Since the change in x changes F PZ , the Q-disk size / segmented QW potential may, at least partly come from the nonrandom alloy potential fluctuation emphasized by the large bowing parameter in InGaN. 2,29,61 For LDs, the effective bandgap inhomogeneity more than 50 meV is too large to obtain an uniform EHP in the well. Indeed, some InGaN MQW LDs showed EHP lasing in tail states.…”

Section: Coulomb Screening Effects By Si-doping Of Gan Barriersmentioning

confidence: 99%

“…1,[25][26][27] On the other hand, several groups have discussed the importance of the quantum confined Stark effect (QCSE) 28 due to the piezoelectric field (F PZ ) in strained wurtzite InGaN QWs. 2,25,[29][30][31] In particular, the blueshift of the electroluminescence (EL) peak in InGaN SQW LEDs 1 with increasing drive current has been explained 1,25 by the combined effects of a reduction of QCSE due to Coulomb screening of F PZ 2,25,29 and band-filling of the energy tail states. 1,25 Moreover, characteristic optical gain mechanisms were reported for InGaN LD wafers 25,[32][33][34] although gain spectra which can be explained by the well-known e-h plasma (EHP) 35 lasing model were reported.…”

Section: Introductionmentioning

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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“…This technique provides a direct measurement of the stress-thickness product during MOVPE of GaN [49]. In attempting to extract band gap energy from a PL measurement for the AlGaInN quaternary system, one is reminded that the determination of band gap energy for GaInN has been a subject of much debate [50]. Indium-related compositional fluctuation is expected to contribute to a Stokes-like shift with a magnitude of less than 100 meV [51].…”

Section: Mocvd Growth Of Quaternary (Algain)n For Uv Optoelectronicsmentioning

confidence: 99%

High Al-Content AlInGaN Devices for Next Generation Electronic and Optoelectronic Applications

Baca¹,

Briggs²,

Allerman³

et al. 2001

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Optical Properties of Strained AlGaN and GaInN on GaN

Abstract: The composition of alloys in strained ternary alloy layers, Al x Ga1- x N (0<x<0.25) and Ga1- x In x N (0<x<0.20), on thick GaN was precisely determined using the high-resolution X-ray diffraction prof… Show more

Cited by 338 publications

References 20 publications

On the Bandstructure in GaInN/GaN Heterostructures - Strain, Band Gap and Piezoelectric Effect

On the Bandstructure in GaInN/GaN Heterostructures - Strain, Band Gap and Piezoelectric Effect

Spectroscopic Studies in InGaN Quantum Wells

High Al-Content AlInGaN Devices for Next Generation Electronic and Optoelectronic Applications

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