Pollution prevention in the semiconductor industry through recovery and recycling of gallium and arsenic from gaas solid wastes

 A process has been developed for the on-site recovery of both arsenic and gallium from gallium arsenide (GaAs) solid wastes. Until the present, very little effort has been made to attempt to recycle any but the largest-sized pieces of such wastes back into the crystal-growing process. Even when recovery is attempted, all of the effort has been focused on the high-value gallium and no efforts have been made for recovery and reuse of the toxic constituent arsenic. The process described herein first involves the thermal separation of GaAs solid wastes into their constituent elements (with a minimum of energy input or additional handling). Each of the separated elements is then purified to the required levels for further crystal growth using low-cost procedures. Because of this three step approach, the developed procedure can accommodate a wide range of input material characteristics. Prior work with GaAs thermal separation and constituent element purification provided a template for the development of this process, and subsequent thermodynamic consideration of each of these unit operations provided a theoretical basis for process optimization. A patent application for the developed process has been submitted to the United States Patent Office. This paper details the development of the thermal separation process, with important design specifications.