Application of Damage Constants in Gamma Irradiated Anphoterically Si Doped GaAs LEDs

The effect of gamma irradiation on the electrical and optical properties of amphoterically Si-doped GaAs LEDs has been investigated. The lifetime-damage constant product, tau/sub 0/K/sub ..gamma../, for degradation of the light output at constant low voltage was found to be 7.5 x 10/sup -7/ Rads/sup -1/. However, because of the presence of space charge limited current (SCLC) flow at higher currents, which conform to the practical operating range of 10 to 50 mA, the light output degraded more rapidly than at lower voltages. It is shown that the same value of tau/sub 0/K/sub ..gamma../ can be used to predict the degradation at practical operating currents when the SCLC is taken into account. Consequently, the practical implications of the results are that care must be taken in predicting degradation with a low voltage tau/sub 0/K/sub ..gamma../, and that the doping conditions leading to the presence of the SCLC should be avoided for LEDs that must operate in a radiation environment.