Gallium arsenide can be used to make transistors, much like the more common semiconductor silicon. GaAs based circuits are usually capable of much greater speeds than silicon. Seymour Cray pushed for widespread adoption of the substance in computer chips and used it heavily in the creation of his supercomputers. GaAs is also used in space hardened applications because it is better at withstanding the large amount of radiation in space. There are two major drawbacks to gallium arsenide though. First, it is extremely expensive to use GaAs rather than silicon. Second, due to the arsenic that it contains, it is poisonous and dangerous to work with and to manufacture.