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Photoluminescence studies of a perceived white light emission from a monolithic InGaN/GaN quantum well structure.

Ben-Sedrine N, Esteves TC, Rodrigues J, Rino L, Correia MR, Sequeira MC, Neves AJ, Alves E, Bockowski M, Edwards PR, O'Donnell KP, Lorenz K, Monteiro T - Sci Rep (2015)

Bottom Line: As-grown and thermally annealed samples at high temperature (1000 °C, 1100 °C and 1200 °C) and high pressure (1.1 GPa) were analysed by spectroscopic techniques, and the annealing effect on the photoluminescence is deeply explored.Under laser excitation of 3.8 eV at room temperature, the as-grown structure exhibits two main emission bands: a yellow band peaked at 2.14 eV and a blue band peaked at 2.8 eV resulting in white light perception.The room temperature white emission is studied as a function of incident power density, and the correlated colour temperature values are found to be in the warm white range: 3260-4000 K.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Física e I3N, Universidade de Aveiro, Campus Universitário de Santiago,3810-193 Aveiro, Portugal.

ABSTRACT
In this work we demonstrate by photoluminescence studies white light emission from a monolithic InGaN/GaN single quantum well structure grown by metal organic chemical vapour deposition. As-grown and thermally annealed samples at high temperature (1000 °C, 1100 °C and 1200 °C) and high pressure (1.1 GPa) were analysed by spectroscopic techniques, and the annealing effect on the photoluminescence is deeply explored. Under laser excitation of 3.8 eV at room temperature, the as-grown structure exhibits two main emission bands: a yellow band peaked at 2.14 eV and a blue band peaked at 2.8 eV resulting in white light perception. Interestingly, the stability of the white light is preserved after annealing at the lowest temperature (1000 °C), but suppressed for higher temperatures due to a deterioration of the blue quantum well emission. Moreover, the control of the yellow/blue bands intensity ratio, responsible for the white colour coordinate temperatures, could be achieved after annealing at 1000 °C. The room temperature white emission is studied as a function of incident power density, and the correlated colour temperature values are found to be in the warm white range: 3260-4000 K.

No MeSH data available.


Normalized PL spectra of the as-grown, HTHP-1000, HTHP-1100 and HTHP-1200 samples at 14 K (a) and RT (b) obtained with 325 nm laser excitation.
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f1: Normalized PL spectra of the as-grown, HTHP-1000, HTHP-1100 and HTHP-1200 samples at 14 K (a) and RT (b) obtained with 325 nm laser excitation.

Mentions: Figure 1 shows normalized PL spectra of the as-grown, HTHP-1000, HTHP-1100 and HTHP-1200 samples at 14 K [Fig. 1 (a)] and RT [Fig. 1 (b)] obtained with 325 nm photon excitation and a power of I0 × 0.5. The oscillations in the PL spectra are related to Fabry-Perot optical interference within the structure. This Fabry-Perot effect results from the high refractive index contrasts especially between the layers and the substrate19 and modulates all the spectra. It is interesting to note that HTHP annealing at the different temperatures significantly changes the optical properties of the sample. At low temperature (14 K), the spectra of the as-grown and HTHP-1000 samples exhibit the QW blue band (BB) emission peaked at 2.8 eV (442 nm); its broadening (below 100 meV) is compatible with previously reported values20. For higher HTHP annealing temperatures (1100 and 1200 °C), the BB becomes undetectable indicating that such post-growth annealing temperatures might have affected the QW structure. On the high energy side, GaN near-band-edge (NBE) emission due to free and bound exciton transitions (at 3.48 eV), donor-acceptor pair (DAP) recombination and their phonon replicas2122 are observed for all samples. Additionally, on the low energy side of the QW recombination, the broad yellow band (YB) is also identified with negligible intensity when compared with the BB intensity. It can be seen that the intensity ratio of the BB/DAP transitions is decreasing after HTHP annealing at 1000 °C. At RT, for the as-grown and HTHP-1000 samples, the BB persists at 2.8 eV, without any shift of the peak position compared to low temperature. In addition, for all samples, most of the DAP transitions thermally quench, and only the NBE (peaking at about 3.42 eV as expected from the shrinking of the GaN bandgap) and the broad YB centred at 2.14 eV (580 nm) are observed. Unstructured broad emission bands are well-known to occur in GaN samples due to the different nature of defects and typically involving deep defect levels22232425262728. In undoped and doped GaN layers, the most accepted models for the YB recombination involve a DAP or free-to-bound (e-A) transition related to the presence of the native defect VGa and its complexes (e.g. VGaON) in the nitride host22232425262728. It should be emphasized that, after HTHP annealing at 1000 °C, the intensity of the YB increases with respect to the as-grown sample, indicating that annealing in such conditions has promoted the contribution of the GaN deep defects to the emission. Since the samples annealed at 1100 °C and 1200 °C show only YB luminescence at RT, we will focus our analysis on the as-grown and HTHP-1000 samples.


Photoluminescence studies of a perceived white light emission from a monolithic InGaN/GaN quantum well structure.

Ben-Sedrine N, Esteves TC, Rodrigues J, Rino L, Correia MR, Sequeira MC, Neves AJ, Alves E, Bockowski M, Edwards PR, O'Donnell KP, Lorenz K, Monteiro T - Sci Rep (2015)

Normalized PL spectra of the as-grown, HTHP-1000, HTHP-1100 and HTHP-1200 samples at 14 K (a) and RT (b) obtained with 325 nm laser excitation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4559898&req=5

f1: Normalized PL spectra of the as-grown, HTHP-1000, HTHP-1100 and HTHP-1200 samples at 14 K (a) and RT (b) obtained with 325 nm laser excitation.
Mentions: Figure 1 shows normalized PL spectra of the as-grown, HTHP-1000, HTHP-1100 and HTHP-1200 samples at 14 K [Fig. 1 (a)] and RT [Fig. 1 (b)] obtained with 325 nm photon excitation and a power of I0 × 0.5. The oscillations in the PL spectra are related to Fabry-Perot optical interference within the structure. This Fabry-Perot effect results from the high refractive index contrasts especially between the layers and the substrate19 and modulates all the spectra. It is interesting to note that HTHP annealing at the different temperatures significantly changes the optical properties of the sample. At low temperature (14 K), the spectra of the as-grown and HTHP-1000 samples exhibit the QW blue band (BB) emission peaked at 2.8 eV (442 nm); its broadening (below 100 meV) is compatible with previously reported values20. For higher HTHP annealing temperatures (1100 and 1200 °C), the BB becomes undetectable indicating that such post-growth annealing temperatures might have affected the QW structure. On the high energy side, GaN near-band-edge (NBE) emission due to free and bound exciton transitions (at 3.48 eV), donor-acceptor pair (DAP) recombination and their phonon replicas2122 are observed for all samples. Additionally, on the low energy side of the QW recombination, the broad yellow band (YB) is also identified with negligible intensity when compared with the BB intensity. It can be seen that the intensity ratio of the BB/DAP transitions is decreasing after HTHP annealing at 1000 °C. At RT, for the as-grown and HTHP-1000 samples, the BB persists at 2.8 eV, without any shift of the peak position compared to low temperature. In addition, for all samples, most of the DAP transitions thermally quench, and only the NBE (peaking at about 3.42 eV as expected from the shrinking of the GaN bandgap) and the broad YB centred at 2.14 eV (580 nm) are observed. Unstructured broad emission bands are well-known to occur in GaN samples due to the different nature of defects and typically involving deep defect levels22232425262728. In undoped and doped GaN layers, the most accepted models for the YB recombination involve a DAP or free-to-bound (e-A) transition related to the presence of the native defect VGa and its complexes (e.g. VGaON) in the nitride host22232425262728. It should be emphasized that, after HTHP annealing at 1000 °C, the intensity of the YB increases with respect to the as-grown sample, indicating that annealing in such conditions has promoted the contribution of the GaN deep defects to the emission. Since the samples annealed at 1100 °C and 1200 °C show only YB luminescence at RT, we will focus our analysis on the as-grown and HTHP-1000 samples.

Bottom Line: As-grown and thermally annealed samples at high temperature (1000 °C, 1100 °C and 1200 °C) and high pressure (1.1 GPa) were analysed by spectroscopic techniques, and the annealing effect on the photoluminescence is deeply explored.Under laser excitation of 3.8 eV at room temperature, the as-grown structure exhibits two main emission bands: a yellow band peaked at 2.14 eV and a blue band peaked at 2.8 eV resulting in white light perception.The room temperature white emission is studied as a function of incident power density, and the correlated colour temperature values are found to be in the warm white range: 3260-4000 K.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Física e I3N, Universidade de Aveiro, Campus Universitário de Santiago,3810-193 Aveiro, Portugal.

ABSTRACT
In this work we demonstrate by photoluminescence studies white light emission from a monolithic InGaN/GaN single quantum well structure grown by metal organic chemical vapour deposition. As-grown and thermally annealed samples at high temperature (1000 °C, 1100 °C and 1200 °C) and high pressure (1.1 GPa) were analysed by spectroscopic techniques, and the annealing effect on the photoluminescence is deeply explored. Under laser excitation of 3.8 eV at room temperature, the as-grown structure exhibits two main emission bands: a yellow band peaked at 2.14 eV and a blue band peaked at 2.8 eV resulting in white light perception. Interestingly, the stability of the white light is preserved after annealing at the lowest temperature (1000 °C), but suppressed for higher temperatures due to a deterioration of the blue quantum well emission. Moreover, the control of the yellow/blue bands intensity ratio, responsible for the white colour coordinate temperatures, could be achieved after annealing at 1000 °C. The room temperature white emission is studied as a function of incident power density, and the correlated colour temperature values are found to be in the warm white range: 3260-4000 K.

No MeSH data available.