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LED substrate materials basic knowledge of

From: Data:06/02/2016

LED substrate materials:
LED substrate material concept, role, type and performance comparison of
substrate, also known as the substrate, also known as the support substrate.
substrate is mainly the growth of the epitaxial layer of the substrate, in the production and production process, play the role of support and fixation. And the characteristics of the epitaxial layer with a more stringent requirements, otherwise it will influence the growth of the epitaxial layer or the quality of the chip.
LED substrate materials of the type GaN currently available on the market
based series generally have three kinds of materials can be used as substrates: sapphire (Al2O3); silicon (Si); silicon carbide (SiC).
in addition to the above three kinds of commonly used substrate materials, there are GaAs, AlN, ZnO and other materials can also be used as a substrate, usually according to the need to choose the design.
1, sapphire substrate
, GaN based materials and devices are mainly grown on sapphire substrate.
sapphire substrate production technology is mature, the stability of the device better quality
sapphire good can be used in high temperature during the growth of
mechanical strength of sapphire is high, easy to handle and cleaning
lack of
lattice mismatch and thermal mismatch stress, resulting in a large number of defects in the epitaxial layer, at the same time bring difficulties to the follow-up processing device;
sapphire is an insulator, the resistivity is greater than 1011Ω · cm cannot create a device of vertical structure; div>
sapphire hardness is very high, second only to diamond Stone, need of it were thin and cutting, and an increase of a pen, a large investment.
sapphire of heat conduction performance is not very good in the
2, silicon substrate
currently is part of the LED chip using silicon substrate. Chip electrode
silicon substrate using two kinds of contact modes, namely l contact (Lateral-contact, horizontal contact) and V contact (Vertical-contact, the vertical contact), referred to as L type electrode and V type electrode.
through these two kinds of contact, LED chip internal current can be horizontal flow, can also be a vertical flow. As the current can be longitudinally flowing, the luminous area of the LED is increased, and the light emitting efficiency of the LED is improved.
because silicon is a good conductor of heat, the thermal conductivity of the device can be significantly improved, thus prolonging the life of the device.  
3, silicon carbide substrate
SiC is the IV-IV family of two compounds, and is also the only stable solid compound in the element periodic table IV group element, a kind of important semiconductor material.
has excellent thermal, mechanical, chemical and electrical properties, not only produced one of the best materials for high temperature, high frequency and high power electronic devices, and can be used as based on GaN Blue light emitting diode substrate materials.
band gap semiconductor material SiC power device can withstand a higher voltage, greater current, depletion layer can be made thinner, and therefore faster, can make the device smaller, lighter weight. & nbsp;
silicon carbide substrate of heat conductivity (SiC thermal conductivity is 490W/(m· K)) to more than sapphire substrates higher more than 10 times.
using silicon carbide substrate of the chip electrode is L-shaped, two electrode distribution in the surface and bottom of the device, the heat generated can be through the electrode directly derived; at the same time the substrate does not require current diffusion layer, so not light is current diffusion layer of absorbing material, and improve the light efficiency.
but with respect to the sapphire substrate, silicon carbide manufacturing costs are higher, to achieve its commercialization also need to reduce the cost of the corresponding. In addition, SiC substrate absorption of UV light below 380 nm, is not suitable for R & D below 380 nm UV LED.
4, Gan
for GaN growth of the ideal substrate is a GaN single crystal materials, can greatly improve the crystal quality of the epitaxial film, reduce the dislocation density, improve the service life of the device, improve the luminous efficiency, improve the device operating current density.
but it is very difficult to prepare GaN single crystal, so far there is no effective way.
5, zinc oxide
ZnO is able to become a candidate substrate GaN epitaxial, because the two are very striking similarities. The crystal structure of the two is the same, the identification of the crystal lattice is very small, and the band gap is close to the band gap (with a small value, the contact barrier is small).
however, ZnO as a GaN epitaxial substrate is the Achilles heel of the GaN epitaxial growth of the temperature and the atmosphere is easy to break down and corrosion.
at present, ZnO semiconductor material is not used to manufacture optoelectronic devices or high-temperature electronic devices, mainly material quality is not up to the device level and P type doping problem has not been really solve, for the growth of ZnO based semiconductor materials equipment has been developed successfully. & nbsp;
(1) sapphire, silicon and silicon carbide three substrate performance
6, substrate properties of comparison & nbsp;
(2) for growth of GaN substrate material performance of the pros and cons of comparative

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