PHOTO-ESR STUDY OF THE DX TO SHALLOW DONOR CONVERSION IN TE DOPED ALXGA1-XAS

Results of detailed electron spin resonance (ESR) study of Te doped Al xGa1-xAs epilayers with x = 0.41, 0.42, and 0.5 Al fractions are prese nted. It is shown that the ESR signal observed critically depends on c ooling steps and that the shallow donor ESR signal can be observed pri or to illumination. The first ESR study of AlGaAs layers with removed GaAs substrate are presented. The mechanism of the enhanced photosensi tivity of the ESR signal is explained. It is found very paradoxical th at the ESR signals decreases upon the illumination even though shallow donor concentration is increased.