NEUTRON-IRRADIATION INDUCED CHANGES OF THE ELECTROCHEMICAL PROPERTIESOF N-GAAS

Thermal neutron irradiation produces spatially and energetically homog eneous distributed defects in n-GaAs. These defects act as majority ch arge carrier traps and scattering centres and as recombination sites f or photogenerated charge carriers. This leads to a lowering of the cha rge carrier concentration and mobility and to a decrease in the maximu m photocurrent. Additionally, the photocurrent onset potential is furt her shifted in the positive direction versus the flat band potential. Annealing of irradiated samples at temperatures below 600 degrees C le ads to defect annihilation and thus to restoration of the original ele ctrochemical properties. Annealing at temperatures above 600 degrees C results in an arsenic deficient surface with electronic defect states in the band gap in the near-surface region. Recombination at these de fects appears to affect only the maximum photocurrent and not the phot ocurrent onset potential.