Page 258 - Chalcogenide Glasses for Infrared Optics

AMI Infrar ed Crystalline Materials 233

T/C

Heater

As

Quartz
chamber

Heater
T/C
GaAs melt

T/C

Spin

FIGURE 9.15 Vertical Bridgman crystal grower.

improved crystal perfection. Again the crystals produced are not large
in diameter. A comparison of the advantages of all the different methods
from a device standpoint was also discussed in their paper. 20

9.9 Horizontal Bridgman Production of GaAs
Plates at AMI
AMI purchased a horizontal Bridgman machine from Morgan Semi-
conductor in Garland after the company was bought out. The most
experienced operator from Morgan, Dale Welt, came along with the
machine and joined AMI. The machine was very heavy and 12 ft long.
The mounting was direct to the concrete floor. Figure 9.16 illustrates
the horizontal Bridgman method for growing GaAs crystals. The top
diagram is a simplistic illustration of the horizontal Bridgman GaAs
crystal growth process. In the connected two evacuated quartz cham-
bers, there is elemental arsenic on one side and elemental gallium in
a boat. The remoteness of the arsenic chamber allows accurate control
of the arsenic vapor pressure. The boat is usually one-half of a cylinder