Hot-zone in Sapphire Grower

  Sapphire (Sapphire) is a single crystal of alumina (Al2O3). Its optical penetration band is very wide, from near ultraviolet (190nm) to mid infrared.It has good light transmittance. Sapphire crystal has excellent optical properties, mechanical and chemical stability, high strength, high hardness and corrosion resistance. It can work under the harsh conditions near 2000 C, so it is widely used in infrared military equipment, satellite space technology, high intensity laser window material. Its unique lattice structure, excellent mechanical properties and good thermal properties make sapphire crystal become the practical application of semiconductor GaN/Al2O3 light-emitting diode (LED), the most ideal substrate materials such as large-scale integrated circuit SOI and SOS and superconducting nanostructure film. With the continuous and rapid growth of LED TV, LED Monitor, LED NB, LED Phone and LED lighting market in recent years, the demand expansion of the sapphire market for LED substrate has been strongly promoted.

Advantages:

the technology of sapphire substrate is mature and the quality of the device is good.

Sapphire has good stability and can be used in high temperature growth.

Sapphire has high mechanical strength and is easy to handle and clean

Table 1 Comparison of growth technology

The main growth   technology	Advantages	Disadvantages	Application
Czochralski method	High quality (optical grade), low defect density, large size, high production capacity and relatively low cost	The operation is complicated, the consistency is not high and the rate of finished products is low. It is difficult to grow C axle crystal	More than 70% of the sapphire substrates of LED in the whole world。The United States（Rubicon）、Russia（Monocrystal）、South Korea（Astek）
Czochralski method	The growth status easy to be observed, the size easy to be controlled and crystal shape relatively regular	Great density of defects; the use of iraurita crucible required, high cost; and size is limited	Honeywell in Canada (it was acquired in 2008 by China Silian Group), Saint-Gobain in France   and Sapphire enterprise in Japan.
EFG method	The quality is good.	Crystal direction of large size difficult to be adjusted	Namiki in Japan                  Japan's Kyocera
The temperature gradient method	Simple equipment, convenient operation, no mechanical disturbance, stable interface, high rate of finished products, C axle crystal can be grown	No crystal rotation, thermal field difficult to be even; the crystal to be annealed successively, long cycle and high cost; remarkable forced crucible effect	Photoelectric Materials Division of CAS Shanghai Institute of Optics and Fine Mechanics, and Epistone in Shenzhen, China
Vertical gradient freeze method	Simple equipment, high rate of finished products	High crystal defect density	Yunnan sapphire crystal has been put into mass production, but the price is about half of that of the crystal chip grown by kyropulos method
Vertical horizontal gradient freezing	The crystal size (diameter and _x0010_ height) and shape relatively unrestricted	Patent is in the hands of STC South Korea	South Korea (STC)
Heat exchanger method	The crystal diameter is big and quality is high	The crystal is short, the equipment and the process requirements are complex, high cost, high technological requirements and the main problem is that the crystal is easy to crack	The United States Crystal System (acquired by GT-Solar of America in July 2010) and China has started to step into this area.
Sapphire growth technique with micro-pulling and shoulder-expanding at cooled center	Crystal integrity is good; original annealing can be achieved, short cycle and low cost	Vulnerable to the impact of temperature fluctuation and difficult in growth of C axle crystal;	HIT Druid Electronic Technology Co Ltd

 

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