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Suppression of non-radiative surface recombination by N incorporation in GaAs/GaNAs core/shell nanowires.

Chen SL, Chen WM, Ishikawa F, Buyanova IA - Sci Rep (2015)

Bottom Line: However, due to a large surface-to-volume ratio, III-V NWs suffer from severe non-radiative carrier recombination at/near NWs surfaces that significantly degrades optical quality.The observed N-induced suppression of the surface recombination is concluded to be a result of an N-induced modification of the surface states that are responsible for the nonradiative recombination.Our results, therefore, demonstrate the great potential of incorporating GaNAs in III-V NWs to achieve efficient nano-scale light emitters.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Chemistry and Biology, Linköping University, 58183, Linköping, Sweden.

ABSTRACT
III-V semiconductor nanowires (NWs) such as GaAs NWs form an interesting artificial materials system promising for applications in advanced optoelectronic and photonic devices, thanks to the advantages offered by the 1D architecture and the possibility to combine it with the main-stream silicon technology. Alloying of GaAs with nitrogen can further enhance performance and extend device functionality via band-structure and lattice engineering. However, due to a large surface-to-volume ratio, III-V NWs suffer from severe non-radiative carrier recombination at/near NWs surfaces that significantly degrades optical quality. Here we show that increasing nitrogen composition in novel GaAs/GaNAs core/shell NWs can strongly suppress the detrimental surface recombination. This conclusion is based on our experimental finding that lifetimes of photo-generated free excitons and free carriers increase with increasing N composition, as revealed from our time-resolved photoluminescence (PL) studies. This is accompanied by a sizable enhancement in the PL intensity of the GaAs/GaNAs core/shell NWs at room temperature. The observed N-induced suppression of the surface recombination is concluded to be a result of an N-induced modification of the surface states that are responsible for the nonradiative recombination. Our results, therefore, demonstrate the great potential of incorporating GaNAs in III-V NWs to achieve efficient nano-scale light emitters.

No MeSH data available.


Related in: MedlinePlus

(a)–(c) PL spectra of the investigated structures measured at 140 K. The open (filled) symbols represent the deduced fast (slow) PL lifetimes as a function of emission energy. (d)–(f) PL spectra of the investigated structures detected at different time delays after the excitation pulse. The vertical dashed lines mark the FE spectral positions.
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f3: (a)–(c) PL spectra of the investigated structures measured at 140 K. The open (filled) symbols represent the deduced fast (slow) PL lifetimes as a function of emission energy. (d)–(f) PL spectra of the investigated structures detected at different time delays after the excitation pulse. The vertical dashed lines mark the FE spectral positions.

Mentions: Influence of the exciton trapping on the FE dynamics is expected to become less significant at elevated temperatures. Indeed, according to our previous studies29, a temperature increase causes thermal depopulation of the localized states which leads to prevalence of radiative recombination of free excitons/carriers at T > 100 K. Under these conditions, the PL spectra no longer exhibit a red shift with increasing ∆td, as can be seen from Fig. 3 which shows time-resolved PL spectra (the solid curves) and decay times (the symbols) from the investigated structures at 140 K. Similar to that at 5 K, the PL decays remain bi-exponential. They accelerate with increasing T, see also Fig. 4 a where representative PL decays of the FE/free carrier emission at 100 K, 200 K and 300 K are shown. The observed reduction of carrier lifetimes with rising T reflects thermal activation of competing NRR processes degrading the PL efficiency. Simultaneously, the fast PL decay component gains its intensity and becomes dominant at room temperature not only in the core/shell NWs but also in the epilayer structure. Temperature dependences of the deduced lifetimes and the As/Af ratio are shown in Fig. 4b,c, respectively.


Suppression of non-radiative surface recombination by N incorporation in GaAs/GaNAs core/shell nanowires.

Chen SL, Chen WM, Ishikawa F, Buyanova IA - Sci Rep (2015)

(a)–(c) PL spectra of the investigated structures measured at 140 K. The open (filled) symbols represent the deduced fast (slow) PL lifetimes as a function of emission energy. (d)–(f) PL spectra of the investigated structures detected at different time delays after the excitation pulse. The vertical dashed lines mark the FE spectral positions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477342&req=5

f3: (a)–(c) PL spectra of the investigated structures measured at 140 K. The open (filled) symbols represent the deduced fast (slow) PL lifetimes as a function of emission energy. (d)–(f) PL spectra of the investigated structures detected at different time delays after the excitation pulse. The vertical dashed lines mark the FE spectral positions.
Mentions: Influence of the exciton trapping on the FE dynamics is expected to become less significant at elevated temperatures. Indeed, according to our previous studies29, a temperature increase causes thermal depopulation of the localized states which leads to prevalence of radiative recombination of free excitons/carriers at T > 100 K. Under these conditions, the PL spectra no longer exhibit a red shift with increasing ∆td, as can be seen from Fig. 3 which shows time-resolved PL spectra (the solid curves) and decay times (the symbols) from the investigated structures at 140 K. Similar to that at 5 K, the PL decays remain bi-exponential. They accelerate with increasing T, see also Fig. 4 a where representative PL decays of the FE/free carrier emission at 100 K, 200 K and 300 K are shown. The observed reduction of carrier lifetimes with rising T reflects thermal activation of competing NRR processes degrading the PL efficiency. Simultaneously, the fast PL decay component gains its intensity and becomes dominant at room temperature not only in the core/shell NWs but also in the epilayer structure. Temperature dependences of the deduced lifetimes and the As/Af ratio are shown in Fig. 4b,c, respectively.

Bottom Line: However, due to a large surface-to-volume ratio, III-V NWs suffer from severe non-radiative carrier recombination at/near NWs surfaces that significantly degrades optical quality.The observed N-induced suppression of the surface recombination is concluded to be a result of an N-induced modification of the surface states that are responsible for the nonradiative recombination.Our results, therefore, demonstrate the great potential of incorporating GaNAs in III-V NWs to achieve efficient nano-scale light emitters.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Chemistry and Biology, Linköping University, 58183, Linköping, Sweden.

ABSTRACT
III-V semiconductor nanowires (NWs) such as GaAs NWs form an interesting artificial materials system promising for applications in advanced optoelectronic and photonic devices, thanks to the advantages offered by the 1D architecture and the possibility to combine it with the main-stream silicon technology. Alloying of GaAs with nitrogen can further enhance performance and extend device functionality via band-structure and lattice engineering. However, due to a large surface-to-volume ratio, III-V NWs suffer from severe non-radiative carrier recombination at/near NWs surfaces that significantly degrades optical quality. Here we show that increasing nitrogen composition in novel GaAs/GaNAs core/shell NWs can strongly suppress the detrimental surface recombination. This conclusion is based on our experimental finding that lifetimes of photo-generated free excitons and free carriers increase with increasing N composition, as revealed from our time-resolved photoluminescence (PL) studies. This is accompanied by a sizable enhancement in the PL intensity of the GaAs/GaNAs core/shell NWs at room temperature. The observed N-induced suppression of the surface recombination is concluded to be a result of an N-induced modification of the surface states that are responsible for the nonradiative recombination. Our results, therefore, demonstrate the great potential of incorporating GaNAs in III-V NWs to achieve efficient nano-scale light emitters.

No MeSH data available.


Related in: MedlinePlus