Dynamics of ground and excited states of bound excitons in gallium nitride

Korona, K. P.; Wysmołek, A.; Stępniewski, R.; Kühl, J.; Lee, S. K.; Han, Jeong-Yeol

doi:10.1016/j.jlumin.2004.09.044

Cited by 4 publications

(3 citation statements)

References 10 publications

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“…IV͒. This also means that in the present experiments with front surface excitation and detection and using the data from the NP lines it is not possible to establish thermal equilibrium between the detected FE and DBE populations at 2 K, 35 as typically assumed in the rate-equation modeling of TRPL data. 36,37 Since we conclude that the observed initial BE decay is influenced by several processes from the near surface BE population, it is clear that we cannot conclude a value of the radiative decay time for the DBEs from these data for the NP transitions, although unfortunately this is the standard ͑but generally incorrect͒ procedure in the literature for DBEs in semiconductors.…”

Section: B Pl Transients For the No-phonon Fe And Dbe Linesmentioning

confidence: 96%

“…It is clear that during the first nanoseconds there are strong changes in the occupancy of the excited DBE states, which at the lowest temperatures are not in thermal equilibrium with the ground state. 35 In Fig. 7͑a͒ are shown the PL transients at 2 K for the Si-related TET lines involving 2s and 2p donor states, illustrating the drastic difference in the population of the corresponding initial states of the transitions.…”

Section: Decay Characteristics Of the Two-electron Transitionsmentioning

confidence: 97%

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Transient photoluminescence of shallow donor bound excitons in GaN

et al. 2010

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We present a detailed study of photoluminescence transients for neutral donor bound excitons ͑DBEs͒ in GaN, notably the O N donor DBE at 3.4714 eV and the Si Ga DBE at 3.4723 eV. The studied samples are thick strain free nominally undoped bulk GaN samples, with a spectroscopic linewidth Ͻ0.5 meV at 2 K. The photoluminescence ͑PL͒ decay curves for these no-phonon ͑NP͒ lines are strongly nonexponential, and do not allow a proper assessment of the characteristic BE decay time. The decay of the LO-phonon replicas as well as the so-called two-electron transitions ͑TETs͒ at lower energies show a nicely exponential behavior, and allow extraction of DBE decay times of about 1.1 ns for the Si DBE and 1.8 ns for the O DBE, respectively. The initial nonexponential decay behavior of the NP lines has been studied in both the common front surface excitation-detection mode and with detection in transmission through the sample. This initial decay is explained as related to scattering processes in the near surface region, involving the DBEs and free excitons ͑FEs͒. Light scattering processes may also contribute to this complex decay shape. The DBE-LO-phonon decay does not discriminate between the O and Si DBEs because of spectral overlap involving different LO modes. The TET decays at 2 K are very different for transitions related to the DBE ground state and DBE excited states ͑going to p-like donor final states͒, for T Ͼ 10 K thermalization between the DBE ground state and DBE excited states produces a common decay time. Thermalization between free and bound excitons appears to occur above about 20 K, when the DBE decay follows the FE decay. A simple two-level modeling of exciton capture and recombination for the PL decay curves of the FE and the DBEs, as commonly used in the literature, is shown to be generally inadequate. A broad PL background in the TET spectral region is suggested to be related to a radiative Auger process, where the DBEs recombine while leaving the donors ionized.

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Section: B Pl Transients For the No-phonon Fe And Dbe Linesmentioning

confidence: 96%

Section: Decay Characteristics Of the Two-electron Transitionsmentioning

confidence: 97%

Transient photoluminescence of shallow donor bound excitons in GaN

et al. 2010

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“…3,4 A number of results has been reported about donor-bound exciton (DBE) recombination dynamics in GaN. 5,6 At low temperatures, the photoluminescence (PL) decay of DBE transitions is determined mainly by the radiative recombination processes. However, previous studies have shown a large variation in the PL recombination time of DBEs, 7,8 which partly can be explained by a poorer quality of stressed GaN layers grown heteroepitaxially.…”

Section: Introductionmentioning

confidence: 99%

Effect of silicon and oxygen doping on donor bound excitons in bulk GaN

et al. 2011

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Freestanding n-type intentionally doped GaN layers grown by halide vapor phase epitaxy (HVPE) were studied by transient photoluminescence (PL). Concentrations of silicon and oxygen were varied in the range between 10 17 and 10 18 cm −3 , as confirmed by secondary ion mass spectroscopy (SIMS). We show that a reduction of the background silicon concentration by one order of magnitude compared to the background level in undoped samples can be achieved by incorporation of oxygen during the growth. A strong band gap narrowing (BGN) of ∼6 meV was observed with increasing doping in the studied samples. The low temperature PL recombination time for donor-bound excitons (DBEs) was found to depend significantly on donor concentration. A model assuming generation of DBEs by capturing of free excitons by neutral donors explains the experimental results at low temperature. From fitting the experimental DBE lifetime to the model, the donor concentration dependence for O and Si donors could be reproduced. An effective exciton capture cross-section was found to be ∼9.4 × 10 −15 and 1.2 × 10 −14 cm 2 for silicon and oxygen donors, respectively.

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