Semiconductor Growth is carried out in two Electro-Dynamic Gradient Freeze (EDG) 43 Zone Mellen Furnaces, customized to suit the uses of IMR. These are modified Bridgman furnaces, capable of vertical or horizontal growths, but normally used for modified vertical Bridgman (MVB) growth. The temperature gradient is programmed to translate the length of the furnace bore without movement of the furnace or the working charge. Each zone of the furnace is separately controlled to ± 0.1°C throughout the whole process. In the region critical to the growth, a high degree of control in temperature is provided by the 1” heater zones axially, which are further divided in the radial direction to 4 quadrant zones eliminating any radial-non uniformity. Furnace are equipped with remote alarm systems for safety, and are mounted on vibration isolation fixtures. Two main furnaces are routinely operated and are optimized for different purposes.
The first MVB is a Mellen Electro Dynamic Gradient (EDG) Furnace. This is a 3” bore, 43 zone furnace with an active temperature controlled length of 43 inches, reaching temperatures as high as 1150°C. CdZnTe/CdTe crystals of diameters up to 65 mm are routinely grown in this furnace. ADAPT, a software platform from Mellen, is used to control and operate the furnace. Using this furnace, WSU has grown compensated and uncompensated CdTe, CdZnTe and GaAs with less than 200 ppb atomic total impurities (i.e., during synthesis, encapsulation, crucible and growth, cutting and preparation of samples for purity measurements).
Modified Vertical Bridgman Crystal Growth Furnace
The second MVB furnace is the ACRT (Accelerated crucible Rotation Technique) furnace (ACRT-EDG) This is a 4” bore, 43 zone highly modified Mellen furnace with an active temperature controlled length of 43”, reaching temperatures as high as 1200°C, equipped with Pt heating elements. CdZnTe/CdTe crystals of diameter up to 90 mm (~6 kg) are routinely grown in this furnace. This is equipped with a remote alarm system for safety. A custom-made National Instruments control system is used to operate and monitor the growth process. Additionally, it is equipped with variable rate crucible rotation fixture to actively alter growth kinetics for improved crystal quality and homogeneity.