Two-photon absorption and multiphoton-induced photoluminescence of bulk GaN excited below the middle of the band gap

Toda, Yasunori; Matsubara, Takeo; Morita, Ryuji; Yamashita, Mikio; Hoshino, K.; Someya, Takao; Arakawa, Yasuhiko

doi:10.1063/1.1587260

Cited by 26 publications

(18 citation statements)

References 15 publications

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“…Above 1.7 eV, a sudden increase is observed, attributed to resonant enhancement due to the bandgap excitation. This enhancement is consistent with that in the photoluminescence excitation spectrum in the YL band [8]. The estimated TPA coefficient at 1.75 eV is $3 cm/GW, which is also consistent with the value obtained by the other group [2].…”

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confidence: 90%

Efficient two‐photon absorption of bulk GaN in the near‐infrared region

Toda

Matsubara

Morita

et al. 2003

phys. stat. sol. (c)

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Transient transmission changes in the yellow luminescence (YL) band of GaN were investigated using excitation far smaller than the bandgap. At lower excitation power, time-resolved measurements revealed efficient transmission changes due to two-photon absorption (TPA), whose spectrum clearly indicates the contribution of the YL band. Upon increasing the excitation power, the transient signal showed an additional offset signal. The excitation power dependences of the offset suggested a two-step absorption process in conjunction with TPA in the YL band. The excitation energy dependence also supported this conclusion.The study of defect states in GaN films is important for understanding the device physics because even a device grade sample involves a high density of defects. One optical characteristic concerning the defect states is the so-called "yellow luminescence" (YL). So far, several research groups have obtained two-photon and multiple-photon related optical nonlinearities connected with the YL band. . In addition to the study of defect states, these nonlinear absorption studies also provide important insights into the fundamental physics of materials, such as band structures [1], relaxation processes [3-6], and electron-phonon interactions [7]. However, the role of the YL band in these optical nonlinearities remains largely unclear.In this paper, we investigate TPA in the YL band. Transient pump-probe measurements in the nearinfrared (NIR) excitation reveal efficient transmission changes, despite the lack of a bandgap transition. The TPA spectrum clearly shows that the observed large nonlinearity originates from the YL band. In addition, transmission changes at higher excitation power show an additional asymmetrical offset signal. The offset also reflects the characteristic of efficient TPA in the YL band.The sample studied was a freestanding bulk GaN sample with a thickness of $420 mm. The absence of a substrate allows the nonlinear response to be evaluated precisely. The electron concentration in the sample was estimated to be $ 10 19 cm À3 . A mode-locked Ti : sapphire laser (pulse width $100 fs, repetition rate 76 MHz) was employed as an NIR excitation light source. The tunable wavelength of the laser was 1.25 to 1.77 eV, which covers the excitation of carriers from the middle of the YL band to the middle of the energy gap (E G /2) into the conduction band. Linearly polarized pump

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confidence: 90%

Efficient two‐photon absorption of bulk GaN in the near‐infrared region

Toda

Matsubara

Morita

et al. 2003

phys. stat. sol. (c)

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“…The mechanisms for ASPL can be attributed to multiphoton absorption including two-photon absorption, [1][2][3][4][5] Auger fountain process, 6 and the absorption of phonons. The ASPL peaks are observable only at sufficiently low temperatures.…”

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Phonon-assisted ultraviolet anti-Stokes photoluminescence from GaN film grown on Si (111) substrate

Tripathy

et al. 2008

Applied Physics Letters

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Phonon-assisted anti-Stokes photoluminescence (ASPL) in the ultraviolet region has been observed in the GaN film grown on a Si (111) substrate. The ASPL peaks are observable only at sufficiently low temperatures. In addition, even if the photon energy is ≈318meV below the transition energy for bound excitons, the ASPL peaks can be still observed. Based on our analysis, the donor-acceptor pairs and bound excitons have played primary roles in the generation of ASPL. Upon the absorption of photons, the ionizations of the neutral donors and neutral acceptors are assisted by longitudinal-optical phonons.

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“…The deviation of the fitting results from the theoretical values may be attributed to the involvement of the defect states inside the bandgap in the multiphoton transition, which is also observed in GaN material. 19 The contributions of the defect states are not discussed here.…”

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Efficient multiphoton-absorption-induced luminescence in single-crystalline ZnO at room temperature

Dai

Shi

et al. 2005

Opt. Lett.

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Two-photon absorption and multiphoton-induced photoluminescence of bulk GaN excited below the middle of the band gap

Cited by 26 publications

References 15 publications

Efficient two‐photon absorption of bulk GaN in the near‐infrared region

Efficient two‐photon absorption of bulk GaN in the near‐infrared region

Phonon-assisted ultraviolet anti-Stokes photoluminescence from GaN film grown on Si (111) substrate

Efficient multiphoton-absorption-induced luminescence in single-crystalline ZnO at room temperature

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