ABSTRACT
Interest in the materials dates from the 1950s when, because of its high electron mobility, GaAs was first seriously considered as a possible alternative to germanium and silicon for transistor applications. In the 1960s an entirely new line of enquiry was initiated when Gunn discovered that microwave oscillations can be obtained from bulk GaAs when it is subjected to a high electric field. Crystals can be produced within a wide range of electrical conductivity; in particular, very highly resistive material can be made. The difficulty of course, is that in general different compounds will have different values of lattice constant. Unfortunately, the lattice constant of this material would not correspond to that of either of the easily available substrate materials (GaAs and InP). The phenomenon is the basis of the potentially important 'high electron mobility' transistor, currently under development in many laboratories.
