Compensation mechanism and transport behaviour of semi-insulating GaAs:Cu

Semi-insulating conditions are obtained by copper diffusion of n-type GaAs in a conventional compensation process accompanied by an apparent transformation of the EL2 donor into another deep donor that pins the Fermi level. The anomalous temperature dependence of the low electron Hall mobility of the GaAs:Cu samples significantly differs from the usual one in undoped semi-insulating samples. It is suggested that potential fluctuations caused by inhomogeneous impurity distribution in the closely compensated samples may be responsible for the anomalous conduction which is similar to that observed in different types of inhomogeneous semi-insulating material.