The chemical composition of sapphire crystal is alumina, with the crystal structure hexagonal lattice. Sapphire is a commonly used substrate material for gallium nitride (GaN) epitaxial growth. It has ultra-high hardness, stable physical and chemical properties at high temperatures, excellent optical performance.

Generally the GaN-based device is grown on the C-plane <0001> of sapphire (polar plane), which has a strong polarization effect. The strong polarization effect makes the AlGaN / GaN heterojunction interface generates a high density and high mobility two-dimensional electron gas (2-DEG) , which is beneficial to the performance of GaN-based high electron mobility transistors (HEMT ). Ever so, the polarization effect is grately harmful to the optoelectronic device: the energy band is bended and tilted, and the energy level is changed due to the built-in electric field caused by the polarization effect. This kind of strong polarized electric field separates the positive and negative carriers in space, so the overlap of the wave function of the electron and the hole becomes smaller, all of these significantly reduces the luminous efficiency of the material, and leads the red-shift phenomenon.

The semi-polar and non-polar GaN can be grown on the sapphire substrate with some special planes like M-plane <1-100>and R-plane <1-102>. The semi-polar and non-polar GaN have good performance to improve the device droop effect, wavelength shift phenomenon and long wavelength band efficiency of LED device. Studies have shown that using the high-temperature AlN nucleation layer and the higher AlGaN growth temperature, or a buffer layer with the multilayer AlGaN, or using Si doping technique can effectively improve the crystal quality and the dislocation density of semi-polar and non-polar AlGaN thin films grown on sapphire substrates.  

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Standard wafer the most widely used as LED substrate.

2 inch C-plane sapphire wafer thichkness 0.43mm Single sided polished (SSP) /Double sided polished (DSP) 

3 inch C-plane sapphire wafer thichkness 0.60mm SSP/DSP

4 inch C-plane sapphire wafer thichkness 0.65mm SSP/DSP

6 inch C-plane sapphire wafer thichkness 1.0mm SSP/DSP  

Sapphire plate used as carrier, bonding substrate, windows.

2 inch C-plane sapphire wafer thichkness 0.3 mm DSP

4 inch C-plane sapphire wafer thichkness 1.0 mm DSP

Diameter 104mm C-plane sapphire wafer thichkness 1.0 mm DSP (used for bonding with GaAs)

Diameter 156mm C-plane sapphire wafer thichkness 1.0 mm DSP (used for bonding with GaAs)

6 inch C-plane sapphire wafer thichkness 0.5 mm DSP

8 inch C-plane sapphire wafer thichkness 1.0 mm DSP

Sapphire wafer with special orientation.

2 inch / 4 inch A-plane sapphire wafer SSP/DSP

2 inch / 4 inch R-plane sapphire wafer SSP/DSP

2 inch / 4 inch M-plane sapphire wafer SSP/DSP

2 inch / 4 inch C-plane off-cut sapphire wafer SSP/DSP 

More details please download <catalogue> and contact us by email...

Patterned sapphire wafer (PSS)

The PSS technique is using a mask with a periodic sub-microstructure pattern, to transfer the pattern to sapphire substrate by wet etching or dry etching, and finally remove the mask to obtain a patterned sapphire substrate.

The patterned substrate can effectively reduce the linear dislocation density of heteroepitaxial caused by the mismatch of lattice constant and thermal expansion coefficient, and improve the quantum efficiency in the device; The pattern can increase the probability of the photons exiting the device by scattering the photons emitted from the active region,  to improve the light extraction efficiency of the LED device.

At present, micron patterned sapphire substrates have been widely used in LED industry. Compared with LEDs based on non-patterned substrates, the luminous power of PSS-LEDs is increased by about 30%. Due to the different size and shape of the sapphire patterned substrate, which have different effects on the LED device, the PSS technique is still an important research topic in the field of epitaxy research.

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2 inch PSS  |  4 inch PSS

Orientation: C-plane (0001) off angle 0.2 ± 0.1º (M axis)

Thickness: 430um

Pattern type: Cone

Pattern H: 1.6-1.8um

Pattern W: 2.7-2.85um

Pattern W: 3.0±0.1um

TTV<10um 

More details please download <catalogue> and contact us by email...

The Blue / Green LED on sapphire substrate

The working principle of LED is that the electrons and holes injected into the P / N section of the diode meet and recombine in the case of forward conduction, converting the potential energy into light energy. The wavelength of the emitted photon (that is, the color of the light) is determined by the energy band width of the semiconductor. The current material base of the blue and green LED is a group III nitride semiconductor, that is a AlGaInN alloy system with GaN and InNAlN.

To epitaxially grow a GaN film on a sapphire substrate, the first step is to epitaxial a GaN buffer layer on the substrate (epitaxial GaN nucleation layer with low temperature, then epitaxial u-GaN buffer layer with high temperature); the second step is to grow n-GaN ( Si-doped ) to provide electron injection; the third step is to grow a multi-functional quantum well (MQW) to provide a radiation recombination center, in which the electrons and holes recombine; the fourth step is to grow a p-GaN layer (Mg-doped) to provide hole injection. Here is a common structure of Horizontal LED in the figure:

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Green LED substrate  |  Blue LED substrate

Substrate: 4inch SSP/DSP sapphire

Thickness of epitaxial layer: < 5000nm

WP: 520-530nm（Green）  |  450-460nm（Blue）

Bow<150um 

More details please download <catalogue> and contact us by email...

Sapphire as material of optical components and special-shaped parts

Sapphire crystal has the characteristics of high hardness, good light transmittance, electrical insulation, good mechanical properties, stable chemical properties, wear resistance, wind erosion resistance. It can be applied to the materials of high-strength window, microwave tubes, ultrasonic transmission elements, laser cavities, bearings of precision instrument, crucible, blades, etc.

Physical and chemical properties of sapphire:

Crystal structure: Hexagonal lattice a = 4.76Å c = 12.99Å

Melting point 2053 ℃

Density 3.98g / cm3

Hardness 9 (Mohs)

Linear thermal expansion coefficient: 6.7x10-6 / ° C parallel to the С axis, 5.0x10-6 / ° C perpendicular to the С axis

Thermal conductivity: 46.06 @ 0 ℃ 25.12 @ 100 ℃, 12.56@400℃ (W / (m.k))

Heat capacity: 0.10 (cal / ℃)

Refractive index 1.762-1.770

Birefringence 0.008 ~ 0.010

Medium and short wave infrared light transmittance ≥85%

Dielectric constant 9.4@300K A axis~11.58@300K C axis

Insoluble in water, free from acid and alkali corrosion, it can be corroded by hydrofluoric acid, phosphoric acid and molten potassium hydroxide at 300 ℃.

* Sapphire special-shaped parts commonly are customized as per drawings, please contact customer service.