THE ENERGY-DEPENDENCE OF LIFETIME DAMAGE CONSTANTS IN GAAS LEDS FOR 1-500 MEV PROTONS

The energy dependence of lifetime damage constants have been measured in GaAs LEDs for 1 - 500 MeV protons. At energies below about 100 MeV, the dependence is close to that expected based on proportionality bet ween non-ionizing energy loss (NIEL) and damage constants. In the 150 - 500 MeV range, however, a monotonic decrease in damage constant is f ound, at variance with published calculations which show an increase w ith energy. Two possible explanations are suggested; an inadequate mod el for the calculated energy dependence of NIEL, or the creation of da mage clusters which have less effect than the deposition of an equival ent energy in the form of point defects.