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Observation and tunability of room temperature photoluminescence of GaAs/GaInAs core-multiple-quantum-well shell nanowire structure grown on Si (100) by molecular beam epitaxy.

Park KW, Park CY, Ravindran S, Jang JS, Jo YR, Kim BJ, Lee YT - Nanoscale Res Lett (2014)

Bottom Line: The GaAs/GaInAs core-MQW shell NW surrounded by AlGaAs also shows an enhanced PL intensity due to the improved carrier confinement owing to the presence of an AlGaAs clad layer.The inclined growth of the GaAs NWs produces a core-MQW shell structure having a different PL peak position than that of planar QWs.The PL emission by MQW shell and the ability to tune the PL peak position by varying the shell width make such core-shell NWs highly attractive for realizing next generation ultrasmall light sources and other optoelectronics devices. 81.07.Gf; 81.15.Hi; 78.55.Cr.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Information and Communications, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 500-712, Republic of Korea.

ABSTRACT

Unlabelled: We report the observation of room temperature photoluminescence (PL) emission from GaAs/GaInAs core-multiple-quantum-well (MQW) shell nanowires (NWs) surrounded by AlGaAs grown by molecular beam epitaxy (MBE) using a self-catalyzed technique. PL spectra of the sample show two PL peaks, originating from the GaAs core NWs and the GaInAs MQW shells. The PL peak from the shell structure red-shifts with increasing well width, and the peak position can be tuned by adjusting the width of the MQW shell. The GaAs/GaInAs core-MQW shell NW surrounded by AlGaAs also shows an enhanced PL intensity due to the improved carrier confinement owing to the presence of an AlGaAs clad layer. The inclined growth of the GaAs NWs produces a core-MQW shell structure having a different PL peak position than that of planar QWs. The PL emission by MQW shell and the ability to tune the PL peak position by varying the shell width make such core-shell NWs highly attractive for realizing next generation ultrasmall light sources and other optoelectronics devices.

Pacs: 81.07.Gf; 81.15.Hi; 78.55.Cr.

No MeSH data available.


Related in: MedlinePlus

BF TEM, HRTEM, and HAADF STEM images of GaAs/GaInAs core-shell nanowire and spot EDX data. (a) BF TEM image of a GaAs/GaInAs core-shell nanowire (GaInAs/GaAs/AlGaAs on GaAs core NW) and (b) HRTEM image of the GaInAs layer from the boxed area of the nanowire in Figure 3a. The insets are the FFT patterns from the ZB and WZ structures. (c) HAADF STEM image of the same area of the nanowire shown in Figure 3a. The white line shown in the box represents the region along which the spot EDX was measured. (d) Spot EDX data revealing the atomic weight percentage of the constituent elements of the GaInAs layer of the nanowire shown in Figure 3c. Inset shows the cross-sectional schematic of the nanowire structure shown in Figure 3a. The arrow shown in the inset indicates the layer from which spot EDX is taken.
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Figure 3: BF TEM, HRTEM, and HAADF STEM images of GaAs/GaInAs core-shell nanowire and spot EDX data. (a) BF TEM image of a GaAs/GaInAs core-shell nanowire (GaInAs/GaAs/AlGaAs on GaAs core NW) and (b) HRTEM image of the GaInAs layer from the boxed area of the nanowire in Figure 3a. The insets are the FFT patterns from the ZB and WZ structures. (c) HAADF STEM image of the same area of the nanowire shown in Figure 3a. The white line shown in the box represents the region along which the spot EDX was measured. (d) Spot EDX data revealing the atomic weight percentage of the constituent elements of the GaInAs layer of the nanowire shown in Figure 3c. Inset shows the cross-sectional schematic of the nanowire structure shown in Figure 3a. The arrow shown in the inset indicates the layer from which spot EDX is taken.

Mentions: Figure 3a shows the bright field (BF) TEM image of the core-shell nanowire grown without the AlGaAs clad layer. The cross-sectional schematic of the nanowire structure is described in the inset of Figure 3d. For this sample, the GaInAs well layer and one of the GaAs barrier layer is present, while the second GaAs barrier layer and the outermost AlGaAs clad layer are absent. The diameter of the nanowire was approximately 450 nm, and the expected width of GaInAs well was 16 nm. The selected area diffraction (SAD) pattern in the inset of Figure 3a indicates that the grown nanowire is crystalline having a mixture of ZB and WZ crystalline structures due to the comparable-free energies of WZ and ZB in large diameter NWs [33]. The stacking faults located between the two structures give rise to the streaks shown in the SAD pattern. By comparing the diffraction pattern with the BF image, we find that the nanowire is grown along [111] of the ZB structure which is equivalent with [0001] in the WZ structure. Figure 3b shows the high-resolution transmission electron microscopy (HRTEM) image of the GaInAs layer from the boxed area of the nanowire shown in Figure 3a, and the fast Fourier transform (FFT) images as insets in Figure 3b. From these, we can identify the two different nanowire sections, i.e., ZB and WZ structures, which are confirmed by the FFT patterns of the corresponding areas. Moreover, we note that the FFTs of the outermost layer correspond to the diffraction pattern of the entire layers shown in Figure 3a, indicating that the shell layer is deposited epitaxially on the core nanowire. Figure 3c shows the high-angle annular dark field scanning transmission electron microscopy (HAADF) STEM image of the boxed area of the nanowire shown in Figure 3a. HAADF STEM image was used for composition analysis over TEM image due to the former’s higher sensitivity to the variation in the atomic number of atoms and/or relative differences in the electron density distribution of the samples. Spot EDX measurements were carried out to determine the constituent elements as well as the composition of the GaInAs well layers.


Observation and tunability of room temperature photoluminescence of GaAs/GaInAs core-multiple-quantum-well shell nanowire structure grown on Si (100) by molecular beam epitaxy.

Park KW, Park CY, Ravindran S, Jang JS, Jo YR, Kim BJ, Lee YT - Nanoscale Res Lett (2014)

BF TEM, HRTEM, and HAADF STEM images of GaAs/GaInAs core-shell nanowire and spot EDX data. (a) BF TEM image of a GaAs/GaInAs core-shell nanowire (GaInAs/GaAs/AlGaAs on GaAs core NW) and (b) HRTEM image of the GaInAs layer from the boxed area of the nanowire in Figure 3a. The insets are the FFT patterns from the ZB and WZ structures. (c) HAADF STEM image of the same area of the nanowire shown in Figure 3a. The white line shown in the box represents the region along which the spot EDX was measured. (d) Spot EDX data revealing the atomic weight percentage of the constituent elements of the GaInAs layer of the nanowire shown in Figure 3c. Inset shows the cross-sectional schematic of the nanowire structure shown in Figure 3a. The arrow shown in the inset indicates the layer from which spot EDX is taken.
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Figure 3: BF TEM, HRTEM, and HAADF STEM images of GaAs/GaInAs core-shell nanowire and spot EDX data. (a) BF TEM image of a GaAs/GaInAs core-shell nanowire (GaInAs/GaAs/AlGaAs on GaAs core NW) and (b) HRTEM image of the GaInAs layer from the boxed area of the nanowire in Figure 3a. The insets are the FFT patterns from the ZB and WZ structures. (c) HAADF STEM image of the same area of the nanowire shown in Figure 3a. The white line shown in the box represents the region along which the spot EDX was measured. (d) Spot EDX data revealing the atomic weight percentage of the constituent elements of the GaInAs layer of the nanowire shown in Figure 3c. Inset shows the cross-sectional schematic of the nanowire structure shown in Figure 3a. The arrow shown in the inset indicates the layer from which spot EDX is taken.
Mentions: Figure 3a shows the bright field (BF) TEM image of the core-shell nanowire grown without the AlGaAs clad layer. The cross-sectional schematic of the nanowire structure is described in the inset of Figure 3d. For this sample, the GaInAs well layer and one of the GaAs barrier layer is present, while the second GaAs barrier layer and the outermost AlGaAs clad layer are absent. The diameter of the nanowire was approximately 450 nm, and the expected width of GaInAs well was 16 nm. The selected area diffraction (SAD) pattern in the inset of Figure 3a indicates that the grown nanowire is crystalline having a mixture of ZB and WZ crystalline structures due to the comparable-free energies of WZ and ZB in large diameter NWs [33]. The stacking faults located between the two structures give rise to the streaks shown in the SAD pattern. By comparing the diffraction pattern with the BF image, we find that the nanowire is grown along [111] of the ZB structure which is equivalent with [0001] in the WZ structure. Figure 3b shows the high-resolution transmission electron microscopy (HRTEM) image of the GaInAs layer from the boxed area of the nanowire shown in Figure 3a, and the fast Fourier transform (FFT) images as insets in Figure 3b. From these, we can identify the two different nanowire sections, i.e., ZB and WZ structures, which are confirmed by the FFT patterns of the corresponding areas. Moreover, we note that the FFTs of the outermost layer correspond to the diffraction pattern of the entire layers shown in Figure 3a, indicating that the shell layer is deposited epitaxially on the core nanowire. Figure 3c shows the high-angle annular dark field scanning transmission electron microscopy (HAADF) STEM image of the boxed area of the nanowire shown in Figure 3a. HAADF STEM image was used for composition analysis over TEM image due to the former’s higher sensitivity to the variation in the atomic number of atoms and/or relative differences in the electron density distribution of the samples. Spot EDX measurements were carried out to determine the constituent elements as well as the composition of the GaInAs well layers.

Bottom Line: The GaAs/GaInAs core-MQW shell NW surrounded by AlGaAs also shows an enhanced PL intensity due to the improved carrier confinement owing to the presence of an AlGaAs clad layer.The inclined growth of the GaAs NWs produces a core-MQW shell structure having a different PL peak position than that of planar QWs.The PL emission by MQW shell and the ability to tune the PL peak position by varying the shell width make such core-shell NWs highly attractive for realizing next generation ultrasmall light sources and other optoelectronics devices. 81.07.Gf; 81.15.Hi; 78.55.Cr.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Information and Communications, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 500-712, Republic of Korea.

ABSTRACT

Unlabelled: We report the observation of room temperature photoluminescence (PL) emission from GaAs/GaInAs core-multiple-quantum-well (MQW) shell nanowires (NWs) surrounded by AlGaAs grown by molecular beam epitaxy (MBE) using a self-catalyzed technique. PL spectra of the sample show two PL peaks, originating from the GaAs core NWs and the GaInAs MQW shells. The PL peak from the shell structure red-shifts with increasing well width, and the peak position can be tuned by adjusting the width of the MQW shell. The GaAs/GaInAs core-MQW shell NW surrounded by AlGaAs also shows an enhanced PL intensity due to the improved carrier confinement owing to the presence of an AlGaAs clad layer. The inclined growth of the GaAs NWs produces a core-MQW shell structure having a different PL peak position than that of planar QWs. The PL emission by MQW shell and the ability to tune the PL peak position by varying the shell width make such core-shell NWs highly attractive for realizing next generation ultrasmall light sources and other optoelectronics devices.

Pacs: 81.07.Gf; 81.15.Hi; 78.55.Cr.

No MeSH data available.


Related in: MedlinePlus