Gallium vacancy production in carbon, oxygen, and arsenic irradiated n-type gallium arsenide

Ion implantation of semiconductors results in the introduction of vacancies, interstitials, antisites (in compound semiconductors) and complexes involving these defects. The donor to gallium vacancy (D-->V-Ga) and the free electron to gallium vacancy (e-->V-Ga) transitions occurs at 1.4745 and 1.4785 eV respectively in the photoluminescence (PL) spectrum of irradiated n-type gallium arsenide (GaAs) slightly doped with silicon, when the sample temperature is 4 K (A. Jorio et al., Phys. Rev. B50, pages 1557-1566, 1994). We have implanted 4 mu m thick GaAs films grown on bulk GaAs with carbon, oxygen and arsenic ions in order to determine the V-Ga introduction rate using PL. The particle energy was chosen such that the stopping range covered 2 to 20 mu m. The production rate is in agreement with Rutherford scattering theory, in which only primary knock out processes are considered when the stop-ping range is much greater than the epilayer thickness, but less than the theory when the particles are implanted in the epilayer. Since vacancies are created by both primary and secondary ion collisions and removed by recombinations, the data suggests that secondary ion collisions and recombinations are unimportant at high energies when the particles go right through the samples, or that their effects cancel out. At low energies, when implantation occurs, the combined data suggests that vacancies are removed thorough recombinations at a faster rate than they are produced by secondary ions collisions.