Antilocalization Effect on Photo-Generated Carriers in Semi-Insulating Gaas Sample

Magnetoresistance measurements were performed on an illuminated semi-insulating GaAs sample with intrinsic deep level defects. Electrical carriers were photo-generated under light excitation and positive magnetoresistance for B < 0.2 T was observed in the whole range of temperatures measured (220-315 K). Using the model developed by H. Fukuyama and K. Hoshino, we interpreted the positive magnetoresistance as mainly caused by weak antilocalization effects over hole carriers for T> 240 K. The high disorder originated from the low temperature growth of the sample leads to the strong localization of carriers and gives rise to the positive magnetoresistance observed at temperatures as high as room temperature