Defect Levels in Neutron-Irradiated GaAs Schottky Diodes and Laser Diode Degradation.

摘要

GaAs Schottky and laser diodes are irradiated with high energy neutrons and the resultant trap and defect structure analyzed. The Schottky diodes are irradiated with a clean high-energy neutron beam from a Van de Graaff accelerator,and the laser irradiation is done in a nuclear reactor. The defect structure is shown to consist of energetically discrete trap levels,but the levels are found not to operate independently. A new defect model is proposed based on coupled defect levels and is shown to be in good agreement with the observations. On the basis of this model,values for the discrete trap levels are determined. Experimentally,Schottky diodes are cooled to temperatures in the region 78K,to 178K,the back bias is turned off and on again,and the capacitance versus time (capacitance decay) is monitored. These measurements are used to derive the activation energies of the trap levels. Trap levels are found at 175, 220, 325, 380and 460mV below the conduction band. Several general numerical techniques are developed for the purpose of fitting experimental data to both the independent-level and coupled-level decay models. (Author)