Deep-level defects and diffusion length measurements in low energy proton-irradiated GaAs

A detailed characterization of deep-level defects induced by low energy proton irradiation in n-GaAs LPE layer using AlGaAs-GaAs mesa structure has been carried out for several proton energies (i.e., 50 100 and 290 kev) and fluences (i.e., 10¹⁰, 10¹¹, and 10¹² p/cm²), using DLTS, SEM-EBIC, I-V and C-V measurement techniques. Important defect and recombination parameters such as density and energy level of electron and hole traps, thermal emission rates and capture cross sections for electrons and holes in each trap level as well as hole diffusion lengths in the n-GaAs LPE layer were deduced from these measurements. Hole diffusion lengths determined by the EBIC, DLTS, and I-V measurements are found in good agreement. It is shown that dark current under forward bias condition was dominated by recombination of electron-hole pairs via deep level defects in the junction space charge region of the diode. Significant carrier removal occurs for proton fluence greater than 10¹³p/cm². Research supported by NASA Langley Research Center under grant No. NSG-1425.