GT Advanced Technologies Inc fka GTAT

[Netsurfer]

Tera Xtal was one of several customers in Asia. HTOT was a large customer that ordered 360 systems and only received 150. Link to other customers are in the attached link for reference. The link is dated.....October 2014......but the customers mentioned should be valid.
http://www.wantchinatimes.com/news-subclass-cnt.aspx?id=20141014000114&cid=1102

The seeds are hockey puck shaped cylinders of single crystal sapphire that are typically harvested from a boule. Getting the initial material in the proper crystal orientation can be a challenge. GT typically required customers to buy seeds from them in order to assure that proper yields were met. Off axis seeds could result in reduce yields. Picture stacking LEGOS in a barrel.
If the bottom is not flat the LEGOs will stack at an angle to the side walls while they are supposed to stack parallel to the side walls.

The single crystal seed is placed in the bottom of a crucible...typically made of Molybdenum. The crucible is then topped off with 99.999% pure Al2O3 crushed to various sizes to optimize packing density.

The crucible is then put in the furnace and heated to melt the feed stock......the crushed Alumina. The trick / art is to fully melt the stock without melting the seed as the seed defines the crystal orientation of the boule. As the liquid Alumina freezes it follows the crystal lattice of the seed. The recipe for the heat extraction is a trial and error process .......once a thermal baseline model has established a starting point.

Each boule size had its own recipe and could have had varying size seed pucks to compensate for the larger charge and melt time.

This may be old news to some and informative to others.