| 1. |
- Buyanova, Irina A, et al.
(author)
-
Effects of Ga doping on optical and structural properties of ZnO epilayers
- 2009
-
In: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 45:4-5, s. 413-420
-
Journal article (peer-reviewed)abstract
- Effects of Ga incorporation on electrical, structural and optical properties of ZnO epilayers are systematically studied by employing structural and optical characterization techniques combined with electrical and secondary ion mass spectrometry measurements. A non-monotonous dependence of free electron concentrations on Ga content is observed and is attributed to defect formation and phase separation. The former process is found to dominate for Ga concentrations of around 2-3x1020 cm-3. corresponding defects are suggested to be responsible for a broad red emission, which peaks at around 1.8 eV at K. Characteristic properties of this emission are well accounted for by assuming intracenter transitions at a deep center, of which the associated Huang-Rhys factor and mean phonon energy are determined. For higher Ga doping levels, the phase separation is found to be significant. It is that under these conditions only a minor fraction of incorporated Ga atoms form shallow donors, which leads to the observed dramatic decrease of carrier concentration.
|
|
| 2. |
- Lim, W., et al.
(author)
-
Migration and Luminescence Enhancement Effects of Deuterium in ZnO/ZnCdO Quantum Wells
- 2008
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92, s. 032103-
-
Journal article (peer-reviewed)abstract
- ZnO/ZnCdO/ZnO multiple quantum well samples grown on sapphire substrates by molecular beam epitaxy and annealed in situ were exposed to D2 plasmas at 150 °C. The deuterium showed migration depths of ~0.8 µm for 30 min plasma exposures, with accumulation of 2H in the ZnCdO wells. The photoluminescence (PL) intensity from the samples was increased by factors of 5 at 5 K and ~20 at 300 K as a result of the deuteration, most likely due to passivation of competing nonradiative centers. Annealing up to 300 °C led to increased migration of 2H toward the substrate but no loss of deuterium from the sample and little change in the PL intensity. The initial PL intensities were restored by annealing at >=400 °C as 2H was evolved from the sample (~90% loss by 500 °C). By contrast, samples without in situ annealing showed a decrease in PL intensity with deuteration. This suggests that even moderate annealing temperatures lead to degradation of ZnCdO quantum wells.
|
|
| 3. |
- Luo, Ziyu, et al.
(author)
-
An Efficient Deep-Subwavelength Second Harmonic Nanoantenna Based on Surface Plasmon-Coupled Dilute Nitride GaNP Nanowires
- 2021
-
In: Nano Letters. - : AMER CHEMICAL SOC. - 1530-6984 .- 1530-6992. ; 21:8, s. 3426-3434
-
Journal article (peer-reviewed)abstract
- High-index semiconductor nanoantennae represent a powerful platform for nonlinear photon generation. Devices with reduced footprints are pivotal for higher integration capacity and energy efficiency in photonic integrated circuitry (PIC). Here, we report on a deep subwavelength nonlinear antenna based on dilute nitride GaNP nanowires (NWs), whose second harmonic generation (SHG) shows a 5-fold increase by incorporating similar to 0.45% of nitrogen (N), in comparison with GaP counterpart. Further integrating with a gold (Au) thin film-based hybrid cavity achieves a significantly boosted SHG output by a factor of similar to 380, with a nonlinear conversion efficiency up to 9.4 x 10(-6) W-1. In addition, high-density zinc blende (ZB) twin phases were found to tailor the nonlinear radiation profile via dipolar interference, resulting in a highly symmetric polarimetric pattern well-suited for coupling with polarization nano-optics. Our results manifest dilute nitride nanoantenna as promising building blocks for future chip-based nonlinear photonic technology.
|
|
| 4. |
|
|
| 5. |
- Buyanova, Irina, 1960-, et al.
(author)
-
Effects of hydrogen on the optical properties of ZnCdO/ZnO quantum wells grown by molecular beam epitaxy
- 2008
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92, s. 261912-
-
Journal article (peer-reviewed)abstract
- Temperature-dependent cw- and time-resolved photoluminescence (PL), as well as optically detected magnetic resonance (ODMR) measurements are employed to evaluate effects of deuterium (2H) doping on optical properties of ZnCdO/ZnO quantum well structures grown by molecular beam epitaxy. It is shown that incorporation of 2H from a remote plasma causes a substantial improvement in radiative efficiency of the investigated structures. Based on transient PL measurements, the observed improvements are attributed to efficient passivation by hydrogen of competing nonradiative recombination centers via defects. This conclusion is confirmed from the ODMR studies.
|
|
| 6. |
- Buyanova, Irina, 1960-, et al.
(author)
-
Optical characterization of Zn(1-x)Cd(x)O alloys grown by molecular-beam epitaxy
- 2006
-
In: 210th ECS Meeting Volume 3, Issue 5. - : The Electrochemical Society. ; , s. 391-398
-
Conference paper (other academic/artistic)abstract
- We have carried out comprehensive optical studies to evaluate structural and bandgap properties of Zn1-xCdxO alloys with x{less than or equalto}0.17 grown by molecular beam epitaxy. High crystalline quality ofthe alloys was concluded from cathodoluminescence measurements. Based on absorptionand reflectance measurements, the compositional dependence of the bandgap energyof ZnCdO, estimated without taking into account excitonic effects, wasfound to follow the trend Eg(x)=3.28-2.23x+0.45x2. Degradation in the alloyquality due to possible phase separation was found to causedeviations from this trend, evident from a more rapid redshift of the absorption edge. Effects of Cd incorporation onthe variation of the bandgap energies with temperature are alsodiscussed.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Dagnelund, Daniel, 1980-, et al.
(author)
-
Effect of growth conditions on grown-in defect formation and luminescence efficiency in GaInNP epilayers grown by molecular-beam epitaxy.
- 2008
-
In: Physica status solidi (c)Special Issue: E-MRS 2007 Spring Meeting – Symposium F and Conference on Photonic Materials. - Weinheim : Wiley-VCH Verlagsgesellschaft. ; , s. 460-463
-
Conference paper (peer-reviewed)abstract
- A detailed study of the impact of different growth conditions (i.e. ion bombardment, nitrogen flow and In content) on the defect formation in Ga(In)NP epilayers grown on GaP substrates by solid-source molecular beam epitaxy is performed. Reduced nitrogen ion bombardment during the growth is shown to significantly reduce formation of defects acting as competing recombination centers, such as a Ga interstitial defect and other unidentified defects revealed by optically detected magnetic resonance. Further, high nitrogen flow is found to be even more effective than the ion bombardment in introducing the defects. The incorporation of In by 5.1% is, on the other hand, found not to affect the introduction of defects. The results provide a useful insight into the formation mechanism of the defects that will hopefully shed light on a control of the defect introduction in the alloys by optimizing growth conditions.
|
|
| 10. |
|
|
