University of Bath
Department of Electronic & Electrical Engineering
Core–shell indium gallium nitride (InGaN)/gallium nitride (GaN) structures are attractive as light emitters due to the large nonpolar surface of rod-like cores with their longitudinal axis aligned along the c-direction. These facets do... more
Core–shell indium gallium nitride (InGaN)/gallium nitride (GaN) structures are attractive as light emitters due to the large nonpolar surface of rod-like cores with their longitudinal axis aligned along the c-direction. These facets do not suffer from the quantum-confined Stark effect that limits the thickness of quantum wells and efficiency in conventional light-emitting devices. Understanding InGaN growth on these submicron three-dimensional structures is
important to optimize optoelectronic device performance. In this work, the influence of reactor parameters was determined and compared. GaN nanorods (NRs) with both {11-20} a-plane and {10-10} m-plane nonpolar facets were prepared to investigate the impact of metalorganic vapor phase epitaxy reactor parameters on the characteristics of a thick (38 to 85 nm) overgrown InGaN shell. The morphology and optical emission properties of the InGaN layers were investigated by scanning electron microscopy, transmission electron microscopy, and cathodoluminescence
hyperspectral imaging. The study reveals that reactor pressure has an important impact on the InN mole fraction on the {10-10} m-plane facets, even at a reduced growth rate. The sample grown at 750°C and 100 mbar had an InN mole fraction of 25% on the {10-10} facets of the NRs.
important to optimize optoelectronic device performance. In this work, the influence of reactor parameters was determined and compared. GaN nanorods (NRs) with both {11-20} a-plane and {10-10} m-plane nonpolar facets were prepared to investigate the impact of metalorganic vapor phase epitaxy reactor parameters on the characteristics of a thick (38 to 85 nm) overgrown InGaN shell. The morphology and optical emission properties of the InGaN layers were investigated by scanning electron microscopy, transmission electron microscopy, and cathodoluminescence
hyperspectral imaging. The study reveals that reactor pressure has an important impact on the InN mole fraction on the {10-10} m-plane facets, even at a reduced growth rate. The sample grown at 750°C and 100 mbar had an InN mole fraction of 25% on the {10-10} facets of the NRs.
Controlling the long-range homogeneity of core−shell InGaN/GaN layers is essential for their use in light-emitting devices. This paper demonstrates variations in optical emission energy as low as ∼7 meV·μm −1 along the m-plane facets from... more
Controlling the long-range homogeneity of core−shell InGaN/GaN layers is essential for their use in light-emitting devices. This paper demonstrates variations in optical emission energy as low as ∼7 meV·μm −1 along the m-plane facets from core−shell InGaN/GaN single quantum wells as measured through high-resolution cathodolumines-cence hyperspectral imaging. The layers were grown by metal organic vapor phase epitaxy on etched GaN nanorod arrays with a pitch of 2 μm. High-resolution transmission electron microscopy and spatially resolved energy-dispersive X-ray spectroscopy measurements demonstrate a long-range InN-content and thickness homogeneity along the entire 1.2 μm length of the m-plane. Such homogeneous emission was found on the m-plane despite the observation of short-range compositional fluctuations in the InGaN single quantum well. The ability to achieve this uniform optical emission from InGaN/GaN core−shell layers is critical to enable them to compete with and replace conventional planar light-emitting devices.
- by Philip Shields and +1
- •
- III-V Semiconductors, Nanowires
High-aspect-ratio GaN-based nanostructures are of interest for advanced photonic crystal and core-shell devices. Nanostructures grown by a bottom-up approach are limited in terms of doping, geometry and shape which narrow their potential... more
High-aspect-ratio GaN-based nanostructures are of interest for advanced photonic crystal and core-shell devices. Nanostructures grown by a bottom-up approach are limited in terms of doping, geometry and shape which narrow their potential application areas. In contrast, high uniformity and a greater diversity of shape and design can be produced via a top-down etching approach. However, a detailed understanding of the role of etch process parameters is lacking for creating high-aspect ratio nanorods and nanopores. Here we report a systematic analysis on the role of temperature and pressure on the fabrication of nanorod and nanopore arrays in GaN. Our results show a threshold in the etch behaviour at a temperature of ~125 °C, which greatly enhances the verticality of the GaN nanorods, whilst the modification of the pressure enables a fine tuning of the nanorod profile. For nanopores we show that the use of higher temperatures at higher pressures enables the fabrication of nanopores with an undercut profile. Such a profile is important for controlling the optical field in photonic crystal-based devices. Therefore we expect the ability to create such nanostructures to form the foundation for new advanced LED designs.
- by E. Le Boulbar and +1
- •
- Plasma Engineering, Nanolithography
Controlling the long-range homogeneity of core−shell InGaN/GaN layers is essential for their use in light-emitting devices. This paper demonstrates variations in optical emission energy as low as ∼7 meV·μm −1 along the m-plane facets from... more
Controlling the long-range homogeneity of core−shell InGaN/GaN layers is essential for their use in light-emitting devices. This paper demonstrates variations in optical emission energy as low as ∼7 meV·μm −1 along the m-plane facets from core−shell InGaN/GaN single quantum wells as measured through high-resolution cathodolumines-cence hyperspectral imaging. The layers were grown by metal organic vapor phase epitaxy on etched GaN nanorod arrays with a pitch of 2 μm. High-resolution transmission electron microscopy and spatially resolved energy-dispersive X-ray spectroscopy measurements demonstrate a long-range InN-content and thickness homogeneity along the entire 1.2 μm length of the m-plane. Such homogeneous emission was found on the m-plane despite the observation of short-range compositional fluctuations in the InGaN single quantum well. The ability to achieve this uniform optical emission from InGaN/GaN core−shell layers is critical to enable them to compete with and replace conventional planar light-emitting devices.
Core–shell indium gallium nitride (InGaN)/gallium nitride (GaN) structures are attractive as light emitters due to the large nonpolar surface of rod-like cores with their longitudinal axis aligned along the c-direction. These facets do... more
Core–shell indium gallium nitride (InGaN)/gallium nitride (GaN) structures are attractive as light emitters due to the large nonpolar surface of rod-like cores with their longitudinal axis aligned along the c-direction. These facets do not suffer from the quantum-confined Stark effect that limits the thickness of quantum wells and efficiency in conventional light-emitting devices. Understanding InGaN growth on these submicron three-dimensional structures is important to optimize optoelectronic device performance. In this work, the influence of reactor
parameters was determined and compared. GaN nanorods (NRs) with both {11-20} a-plane and {10-10} m-plane nonpolar facets were prepared to investigate the impact of metalorganic vapor phase epitaxy reactor parameters on the characteristics of a thick (38 to 85 nm) overgrown
InGaN shell. The morphology and optical emission properties of the InGaN layers were investigated by scanning electron microscopy, transmission electron microscopy, and cathodoluminescence
hyperspectral imaging. The study reveals that reactor pressure has an important impact on the InN mole fraction on the f10-10g m-plane facets, even at a reduced growth rate. The sample grown at 750°C and 100 mbar had an InN mole fraction of 25% on the f10-10g facets of the NRs.
parameters was determined and compared. GaN nanorods (NRs) with both {11-20} a-plane and {10-10} m-plane nonpolar facets were prepared to investigate the impact of metalorganic vapor phase epitaxy reactor parameters on the characteristics of a thick (38 to 85 nm) overgrown
InGaN shell. The morphology and optical emission properties of the InGaN layers were investigated by scanning electron microscopy, transmission electron microscopy, and cathodoluminescence
hyperspectral imaging. The study reveals that reactor pressure has an important impact on the InN mole fraction on the f10-10g m-plane facets, even at a reduced growth rate. The sample grown at 750°C and 100 mbar had an InN mole fraction of 25% on the f10-10g facets of the NRs.
We report the ability to control relative InN incorporation in InGaN/GaN quantum wells (QWs) grown on the semi-polar and non-polar facets of a core-shell nanorod LED structure by varying the growth conditions. A study of the... more
We report the ability to control relative InN incorporation in InGaN/GaN quantum wells (QWs) grown on the semi-polar and non-polar facets of a core-shell nanorod LED structure by varying the growth conditions. A study of the cathodoluminescence emitted from series of structures with different growth temperatures and pressures for the InGaN QW layer revealed that increasing the growth pressure had the effect of increasing InN incorporation on the semi-polar facets, while increasing the growth temperature improves the uniformity of light emission from the QWs on the non-polar facets.