IMPROVEMENT OF MINORITY-CARRIER LIFETIME IN GaAsN GROWN BY CHEMICAL BEAM EPITAXY

Minority-carrier lifetime (electron) in p-type GaAsN film is improved by chemical beam epitaxy (CBE) and thermal annealing. Growth rate (GR) in CBE is an important factor to improve minority-carrier lifetime in bulk (tau(B)). For as-grown samples, tau(B) is increased from 3.2 x 10(2) ps (GR = 2 mu m/h) to 9.0 x 10(2) ps (GR = 0.4 mu m/h). The obtained tau(B) is much longer than the minority-carrier lifetime (similar to 10(1) ps) predicted by the reported carrier diffusion length and mobility. This improvement is due to the increase of nonradiative recombination lifetime (tau(NR)) caused by the decrease of nonradiative recombination centers. By thermal annealing, PL lifetime (tau(PL)) is increased. Therefore, CBE and thermal annealing have a high possibility to obtain the minority-carrier lifetime required to solar cells (> 1 ns).