Micro-LED Wafer Based on Bulk GaN Substrate
PAM-XIAMEN offers high-quality GaN-on-GaN Micro-LED wafer with specific parameters as follows. GaN is widely recognized as the most suitable substrate material for the growth of GaN epitaxial films. The use of homogeneous epitaxial growth fundamentally addresses the lattice mismatch and thermal mismatch issues commonly encountered with heterogeneous substrates. By minimizing the stress caused by differences in material properties during the growth process, GaN-on-GaN enables the formation of high-quality GaN epitaxial layers that outperform those grown on heterogeneous substrates.
1. Specification of Micro-LED Epi Wafer on Bulk GaN Substrate
| Item | GaN-on-GaN Micro-LED Epi Wafer for Green and Blue Light |
| Diameter | 2 & 4 inch |
| Substrate | |
| Material | N Type FS GaN |
| Orientation | C plane（0001）off angle toward M-axis 0.55±0.15° |
| Surface Finished | SSP, DSP |
| Epi Layer | |
| Structure | pGaN/MQWs/nGaN |
| Thickness | 3.2±0.5um |
| Surface Roughness | <0.5nm |
| Dislocation Density | 5*107cm-2 |
| Particles（>20um) | <5pcs |
| Wavelength | Blue: 465±10nm; Green: 525±10nm |
| Wavelength FWHMs | Blue: <20nm; Green:<35nm |
2. Comparison Between GaN-on-Sapphire and GaN-on-GaN LED Wafer
The choice of substrate plays a crucial role in determining the performance of GaN-based LEDs. Currently, the light-emitting layer in GaN LEDs is typically composed of GaN and indium gallium nitride (InGaN) materials and is epitaxially grown on sapphire or silicon substrates.
However, heteroepitaxial growth on sapphire or silicon introduces significant challenges due to lattice constant mismatches, resulting in extremely high defect densities (~109–1010 cm–²) in the nitride film. These defects contribute to reduced LED luminous efficiency and overall device performance.
AFM measurements (Fig. 1) comparing the blue LED luminous layers grown on sapphire and GaN substrates reveal striking differences. On sapphire substrates, the luminous layer is riddled with defects, and as the quantum well (QW) thickness increases from 2.7 nm to 15 nm, the size of the defects grows larger. In contrast, on GaN substrates, even at a QW thickness of 15 nm, the surface remains less defects and relatively smooth.
Fig. 1 AFM of Micro-LED Wafer on Sapphire and GaN Substrates: (a) 2.7 nm QW, (b) 6.0 nm QW, (c) 15.0 nm QW
Furthermore, TEM cross-sectional analysis (Fig. 2) of the GaN-on-GaN luminescent layer shows that the interface between the quantum well and quantum barrier remains smooth even at 15 nm QW thickness. This indicates that GaN-on-GaN structures achieve superior material quality, free from the lattice mismatch issues prevalent in GaN-on-sapphire growth.
Fig. 2 TEM Cross-Section of a Blue LED Luminescent Layer Grown on a GaN Bulk Substrate
Additionally, GaN-on-GaN mitigates polarization field effects caused by lattice mismatch, which is another limitation of GaN-on-sapphire. By reducing these effects, GaN-on-GaN improves quantum efficiency and overall LED performance.
3. Advantages of Device Preparation on GaN-on-GaN Micro-LED Wafer
GaN-on-GaN provides several key advantages that enhance device performance and simplify manufacturing processes:
1) Vertical Structure Feasibility
The conductive N-type GaN substrate in GaN-on-GaN enables the production of vertical structures. This eliminates the need for the laser ablation process required in sapphire-based vertical structures, simplifying manufacturing, reducing costs, and improving yields.
2) Enhanced Light Extraction
The N-face surface on the back of the GaN substrate allows for wet etching to create pyramid structures, improving light extraction efficiency. This is critical for optimizing device brightness and efficiency, particularly in high-performance LEDs.
3) Superior Display Uniformity and Brightness
GaN-on-GaN exhibits better display uniformity and higher brightness compared to GaN-on-sapphire. These advantages make GaN-on-GaN Micro-LED display ideal for applications under strong ambient light, such as AR/MR devices.
4) Reduced Defect Density
GaN-on-GaN significantly reduces dislocation density, addressing the non-radiative recombination centers that typically limit device efficiency. This translates to higher quantum efficiency, better thermal performance, and improved device reliability.
Whether you need GaN wafers for research or for industrial applications, please contact us email at [email protected] and [email protected].