PAM XIAMEN offers AlGaN Template on Sapphire or Silicon Substrate. AlGaN (Aluminum Gallium Nitride) is a direct bandgap ternary semiconductor alloy material, and its band gap at room temperature can vary continuously from 3.4eV to 6.2eV depending on the composition of Al. The large forbidden band width and high thermal conductivity of AlGaN epitaxial template determine that it has broad application prospects in high-brightness white light emitting devices, short-wavelength lasers, solar-blind ultraviolet detectors, and high-temperature, high-power electronic devices. More details of AlGaN template wafers, please see below:
1. AlGaN Template Specifications
1.1 AlGaN/Sapphire Template
Al(0.1)Ga(0.9)N Epitaxial Template on Sapphire (C plane), N- type, 10x10x0.5mm Al(0.1)Ga(0.9)N thickness: 200nm+/- 20nm, Production Grade
Al(0.1)Ga(0.9)N Epitaxial Template on Sapphire (C plane), N- type, 2″diameter,Al(0.1)Ga(0.9)N thickness:200nm+/- 20nm, Production Grade
Al(0.1)Ga(0.9)N Epitaxial Template on Sapphire (C plane), P- type, 2″diameter,Al(0.1)Ga(0.9)N thickness:200nm+/- 20nm, Production Grade
1.2 AlGaN on Silicon Template
Si-based AlGaN(20% Al) Template, 6” diameter, Al(20%)GaN thickness 100A~200A
Please note: for AlGaN thin film on Si, there should be 120-150nm AlN buffer between Si substrate and AlGaN.
2. About AlGaN on Sapphire Substrate
Due to the lack of suitable (lattice matching and thermal expansion matching) substrate materials, cheap sapphire substrate (0001) is often chosen as the substrate for epitaxial growth of AlGaN materials. The MOCVD method is mainly adopted for AlGaN on sapphire growth. The early epitaxial growth of AlGaN materials generally used GN materials as the buffer layer. Although the lattice constant difference between GaN and sapphire substrate (0001) is as high as 17%, the current low-temperature nucleation layer technology can easily obtain a GaN epitaxial layer with bright surface and good crystal quality. Growing AlGaN epitaxial materials on a very thick GaN buffer layer, which is greater than 1um, can grow epitaxial layers with better crystal quality. However, when the thickness and Al composition are large, the lattice constant of AIGaN is smaller than that of GaN. Coupled with the large thermal mismatch between the two, the tensile strain existing in the AlGaN epitaxial layer leads to a large number of cracks, which will seriously affect the performance of the device.
Later, someone used a very thin (10-30nm) low-temperature and high-temperature AIN intermediate layer between GaN and AlGaN, and a crack-free AlGaN epitaxial layer with an Al composition greater than 0.4 and a thickness greater than 1um was grown on GaN. The applications of AlGaN/GaN epitaxial materials in optoelectronics include blue-green semiconductor light sources and front-illuminated ultraviolet detectors. Some applications require the growth of AIGaN epilayer on sapphire substrate. For example, the backlight solar-blind AlGaN pin ultraviolet detector requires the substrate to be transparent to the ultraviolet light in the solar-blind spectrum. Since the strong absorption of GaN to ultraviolet light is less than 365nm, the epitaxial material for backlight solar-blind AlGaN pin ultraviolet detector must be grown on a sapphire substrate that is transparent to solar-blind ultraviolet light. Take AlGaN-based UV photodetector for example: for deep ultraviolet light emitting devices with a wavelength less than 340nm, in order to improve the light extraction efficiency, it is necessary to avoid the use of GaN buffer layer, but it should grow an AlGaN nucleation layer deposited on sapphire substrates. Like GaN, AlGaN has a large lattice mismatch with the sapphire substrate. The use of low-temperature nucleation layer technology is a necessary means to grow an AlGaN film on sapphire substrate with good quality.
3. About Growth of AlGaN on Silicon Substrate
AlGaN thin film tends to grown on a heterogeneous substrate. Take the sapphire for example. It is the most common substrate for nanoporous AlGaN template for back-illuminated devices. However, because silicon can obtain back illumination by chemical means and has low cost, silicon substrate, a UV opaque substrate, is also a good choice for growing AlGaN thin film. When the silicon substrate is used for solar-blind PD, the lattice mismatch will cause high dislocation density and crack-initiated stress.
Thick crack-free AlGaN films can be grown on (111) silicon substrates by using substrate patterning and maskless selective area regrowth. It is an important technology that can separate the epitaxial layer from the substrate and allow crack-free growth. Moreover, mask is beneficial to reduce the dislocation density through tilting the direction for growth.
4. Status Quo of AlGaN Epitaxial Template
With the maturity of GaN material research technology in the visible light range and the application of devices, the research of AlGaN template and short-wavelength ultraviolet devices has gradually become a new hot spot in the research of nitride semiconductors.
In the preparation of AlGaN materials, especially in the process of growing high-Al content AlGaN materials, the main challenges faced are AlGaN surface cracking, low surface migration ability of Al atoms, and difficulty in doping. Growth of AlGaN on AlN template substrate can solve the problem of AlGaN cracking. Side epitaxial growth on micron-level trench AlN/sapphire template reduces the dislocation density in AlN by nearly two numbers. The AlN substrate preparation method of the hydride vapor phase epitaxy and physical vapor transport technology has also developed rapidly. A low dislocation density AlN single crystal substrate of less than 2 inches can be provided.
With regard to AlGaN-based ultraviolet and deep ultraviolet detectors, as the Al composition increases, the difficulty of material growth continues to increase, and the performance of the detector decreases.
In terms of deep-ultraviolet LEDs, all-wavelength deep-ultraviolet LEDs can be achieved through continuous improvement of material quality (such as the use of AlN template substrates and insertion layer technology) and optimization of device structure (such as the use of plasmons to improve light extraction efficiency). In this way, the performance of UV and deep UV LEDs has been continuously improved.