Radiation induced carbon complexes in gallium arsenide

Gallium arsenide grown by the metallorganic chemical vapour deposition method and n-doped to various silicon concentrations was irradiated with reactor neutrons (1 MeV equivalent damage in silicon) in the fluence range 0 to 3 × 10¹⁵ cm⁻². Native defects, including carbon which is a residual impurity of the growth method, and those introduced by irradiation, were characterized by photoluminescence (PL) and deep level transient spectroscopy (DLTS). In some samples with fixed doping value, the PL intensity of all the transitions, including that to the carbon impurity increases at low fluence levels before decreasing at high fluence. At higher fluences, the transition to the carbon impurity goes through other maxima. The carbon PL intensity versus fluence curve depends on initial doping. DLTS results reveal the removal of a trap EL12 at low fluences, but the introduction of other traps at higher fluences. The defect introduction rates depend on fluence. We attribute the variation in the carbon PL intensity to an interaction between the defects introduced by the irradiation and the carbon impurity.