Radiation-induced surface degradation of GaAs and high electron mobility transistor structures

Transistor heterostructures with high-carrier-mobility have been studied. It is shown that, as the $\gamma$-irradiation dose $\Phi$ increases, their degradation occurs in the following sequence. (i) At $\Phi<$ 10$^7$ rad, the GaAs surface layer is damaged to a depth of 10 nm due to a $>$ 0.2-eV decrease in the diffusion energy of intrinsic defects and, probably, atmospheric oxygen. (ii) At $\Phi>$ 10$^7$ rad, highly structurally disordered regions larger than 1 $\mu$m are formed near microscopic defects or dislocations. (iii) At $\Phi>$ 10$^8$ rad, there occurs degradation of the internal AlGaAs/InGaAs/GaAs interfaces and the working channel. An effective method for studying the degradation processes in heterostructures is to employ a set of structural diagnostic methods to analyze processes of radiation-induced and aging degradation, in combination with theoretical simulation of the occurring processes.