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 (τ_B). For as-grown samples, τ_B is increased from 3.2 × 10² ps (GR = 2 μm/h) to 9.0 × 10² ps (GR = 0.4 ×m/h). The obtained τ_B is much longer than the minority-carrier lifetime (~10¹ ps) predicted by the reported carrier diffusion length and mobility. This improvement is due to the increase of nonradiative recombination lifetime (τ_NR) caused by the decrease of nonradiative recombination centers. By thermal annealing, PL lifetime (τ_PL) is increased. Therefore, CBE and thermal annealing have a high possibility to obtain the minority-carrier lifetime required to solar cells (> 1 ns).