The Effect of Gamma Irradiation on the Low Temperature Properties of Amphoterically Si-Doped GaAs LED's

The effects of gamma irradiation on the light intensity, total current, spectral characteristics, and radiative decay time as a function of applied voltage at 76 ~ have been studied in amphoterically Si-doped GaAs light-emitting diodes (LED's). At low voltages, both the total current, I, and radi-ative current are due to space charge recombination with the result that, at constant voltage, I increases with gamma dose, r while the light intensity, L, remains constant. At higher voltages, where the radiative current is due to recombination i the neutral p-region, L decreases harply with r at constant voltage. This rapid decrease is due, in part, to the presence of space-charge limited current (SCLC) flow which also leads to a decrease in I with r at constant high voltage. Spectral measurements show that the emission peak energy is proportional to junction voltage at low currents uggesting radiative tunnel ing of carriers in deep tail states. In accordance with the "wavy band" model t'or these diodes, tail states are also responsible for the observed in