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Effect of Eu-implantation and annealing on the GaN quantum dots excitonic recombination.

Peres M, Magalhães S, Fellmann V, Daudin B, Neves AJ, Alves E, Lorenz K, Monteiro T - Nanoscale Res Lett (2011)

Bottom Line: In Eu-implanted SL structures, the GaN QD recombination was found to be dependent on the implantation fluence.Despite the fact that different deexcitation processes occur in undoped and Eu-implanted SL structures, the excitation population mechanisms were seen to be sample-independent.Two main absorption bands with maxima at approx. 4.1 and 4.7 to 4.9 eV are responsible for the population of the optically active centres in the SL samples.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Física e I3N, Universidade de Aveiro, Campus de Santiago, Aveiro, 3810-193, Portugal. tita@ua.pt.

ABSTRACT
Undoped self-assembled GaN quantum dots (QD) stacked in superlattices (SL) with AlN spacer layers were submitted to thermal annealing treatments. Changes in the balance between the quantum confinement, strain state of the stacked heterostructures and quantum confined Stark effect lead to the observation of GaN QD excitonic recombination above and below the bulk GaN bandgap. In Eu-implanted SL structures, the GaN QD recombination was found to be dependent on the implantation fluence. For samples implanted with high fluence, a broad emission band at 2.7 eV was tentatively assigned to the emission of large blurred GaN QD present in the damage region of the implanted SL. This emission band is absent in the SL structures implanted with lower fluence and hence lower defect level. In both cases, high energy emission bands at approx. 3.9 eV suggest the presence of smaller dots for which the photoluminescence intensity was seen to be constant with increasing temperatures. Despite the fact that different deexcitation processes occur in undoped and Eu-implanted SL structures, the excitation population mechanisms were seen to be sample-independent. Two main absorption bands with maxima at approx. 4.1 and 4.7 to 4.9 eV are responsible for the population of the optically active centres in the SL samples.

No MeSH data available.


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Temperature-dependent PL spectra: for sample (a) #987 implanted with 1 × 1015 atoms.cm-2 and annealed at 1100°C and (b) #989 implanted with 1 × 1013 atoms.cm-2 and annealed at 1000°C obtained with 4.7 eV excitation.
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Figure 3: Temperature-dependent PL spectra: for sample (a) #987 implanted with 1 × 1015 atoms.cm-2 and annealed at 1100°C and (b) #989 implanted with 1 × 1013 atoms.cm-2 and annealed at 1000°C obtained with 4.7 eV excitation.

Mentions: Figure 3a shows typical temperature-dependent PL spectra of both optical emitting centres (2.7 and 3.9 eV bands) observed with excitation with photons of 4.7 eV energy. A fast decrease of the intensity of the 2.7-eV emission is seen with increasing temperature from 14 K to RT (I(14 K)/I(RT)~4). On the contrary, the high energy emission peak at 3.9 eV is seen to have an intensity which is nearly constant up to 200 K. A slight increase of the PL intensity was seen for higher temperatures accompanied with a small energy shift of the peak position, commonly observed in small GaN QDs [11]. For the SL implanted with high fluence only, the GaN QD PL band due to the larger blurred GaN QD have strong non-radiative de-excitation processes likely to be due to the defects generated by ion implantation.


Effect of Eu-implantation and annealing on the GaN quantum dots excitonic recombination.

Peres M, Magalhães S, Fellmann V, Daudin B, Neves AJ, Alves E, Lorenz K, Monteiro T - Nanoscale Res Lett (2011)

Temperature-dependent PL spectra: for sample (a) #987 implanted with 1 × 1015 atoms.cm-2 and annealed at 1100°C and (b) #989 implanted with 1 × 1013 atoms.cm-2 and annealed at 1000°C obtained with 4.7 eV excitation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211471&req=5

Figure 3: Temperature-dependent PL spectra: for sample (a) #987 implanted with 1 × 1015 atoms.cm-2 and annealed at 1100°C and (b) #989 implanted with 1 × 1013 atoms.cm-2 and annealed at 1000°C obtained with 4.7 eV excitation.
Mentions: Figure 3a shows typical temperature-dependent PL spectra of both optical emitting centres (2.7 and 3.9 eV bands) observed with excitation with photons of 4.7 eV energy. A fast decrease of the intensity of the 2.7-eV emission is seen with increasing temperature from 14 K to RT (I(14 K)/I(RT)~4). On the contrary, the high energy emission peak at 3.9 eV is seen to have an intensity which is nearly constant up to 200 K. A slight increase of the PL intensity was seen for higher temperatures accompanied with a small energy shift of the peak position, commonly observed in small GaN QDs [11]. For the SL implanted with high fluence only, the GaN QD PL band due to the larger blurred GaN QD have strong non-radiative de-excitation processes likely to be due to the defects generated by ion implantation.

Bottom Line: In Eu-implanted SL structures, the GaN QD recombination was found to be dependent on the implantation fluence.Despite the fact that different deexcitation processes occur in undoped and Eu-implanted SL structures, the excitation population mechanisms were seen to be sample-independent.Two main absorption bands with maxima at approx. 4.1 and 4.7 to 4.9 eV are responsible for the population of the optically active centres in the SL samples.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Física e I3N, Universidade de Aveiro, Campus de Santiago, Aveiro, 3810-193, Portugal. tita@ua.pt.

ABSTRACT
Undoped self-assembled GaN quantum dots (QD) stacked in superlattices (SL) with AlN spacer layers were submitted to thermal annealing treatments. Changes in the balance between the quantum confinement, strain state of the stacked heterostructures and quantum confined Stark effect lead to the observation of GaN QD excitonic recombination above and below the bulk GaN bandgap. In Eu-implanted SL structures, the GaN QD recombination was found to be dependent on the implantation fluence. For samples implanted with high fluence, a broad emission band at 2.7 eV was tentatively assigned to the emission of large blurred GaN QD present in the damage region of the implanted SL. This emission band is absent in the SL structures implanted with lower fluence and hence lower defect level. In both cases, high energy emission bands at approx. 3.9 eV suggest the presence of smaller dots for which the photoluminescence intensity was seen to be constant with increasing temperatures. Despite the fact that different deexcitation processes occur in undoped and Eu-implanted SL structures, the excitation population mechanisms were seen to be sample-independent. Two main absorption bands with maxima at approx. 4.1 and 4.7 to 4.9 eV are responsible for the population of the optically active centres in the SL samples.

No MeSH data available.


Related in: MedlinePlus