Higher resistivities obtained by iron-diffusion into undoped semi-insulating GaAs

A simple diffusion process at low temperatures of 500-550 degrees C can increase the resistivity of GaAs by one order of magnitude; deep accepters of iron on the order of 10(14) cm(-3) were introduced into liquid encapsulated Czochralski(LEC)-grown GaAs wafers from a spin-on source to obtain higher resistivity in the range of 10(8) Omega.cm. Control of the Fermi level onto the middle of the energy gap was accomplished by compensating deep donors of electron level No. 2 (EL2) by the accepters located at E-t - E-v = 0.46 eV. A calculation based on carrier-compensation concurs with the trend in the resistivity variation experimentally obtained by iron-diffusion in the temperature range of 450-600 degrees C.