Spectroscopic studies in InGaN quantum wells

S. F. Chichibu, Takayuki Sota, K. Wada, S. P. DenBaars, S. Nakamura

    Research output: Contribution to journalArticle

    4 Citations (Scopus)

    Abstract

    Fundamental electronic modulations in strained wurtzite III-nitride, in particular In xGa 1-xN, 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<a B. Their Coulomb interaction is more pronounced for F□L<≤□E v.

    Original languageEnglish
    JournalMRS Internet Journal of Nitride Semiconductor Research
    Volume4
    Issue numberSUPPL. 1
    Publication statusPublished - 1999

    Fingerprint

    Excitons
    Semiconductor quantum wells
    Stark effect
    Wave functions
    Absorption spectra
    Polarization
    Bending (forming)
    Valence bands
    Coulomb interactions
    Nitrides
    Ground state
    Electronic structure
    Luminescence
    Electric fields
    Doping (additives)
    Modulation
    LDS 751
    Electrons

    ASJC Scopus subject areas

    • Materials Science(all)

    Cite this

    Chichibu, S. F., Sota, T., Wada, K., DenBaars, S. P., & Nakamura, S. (1999). Spectroscopic studies in InGaN quantum wells. MRS Internet Journal of Nitride Semiconductor Research, 4(SUPPL. 1).

    Spectroscopic studies in InGaN quantum wells. / Chichibu, S. F.; Sota, Takayuki; Wada, K.; DenBaars, S. P.; Nakamura, S.

    In: MRS Internet Journal of Nitride Semiconductor Research, Vol. 4, No. SUPPL. 1, 1999.

    Research output: Contribution to journalArticle

    Chichibu, SF, Sota, T, Wada, K, DenBaars, SP & Nakamura, S 1999, 'Spectroscopic studies in InGaN quantum wells', MRS Internet Journal of Nitride Semiconductor Research, vol. 4, no. SUPPL. 1.
    Chichibu, S. F. ; Sota, Takayuki ; Wada, K. ; DenBaars, S. P. ; Nakamura, S. / Spectroscopic studies in InGaN quantum wells. In: MRS Internet Journal of Nitride Semiconductor Research. 1999 ; Vol. 4, No. SUPPL. 1.
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