Low energy nitrogen ion doping into GaAs using combined ion-beam and molecular-beam epitaxy method

Abstract

Low energy nitrogen (N) ions were irradiated during the epitaxial growth of GaAs using combined ion beam and molecular beam epitaxy (CIBMBE) method as a function of N + ion acceleration energy ( E a) and N + ion beam current density ( I N). E a was varied from 70 to 170 eV I N from 900 pA/cm 2 to 75 nA/cm 2. GaAs growth rate was fixed to 1 μm/h. In 2 K photoluminescence (PL) spectra of the samples with I N = 3 nA/cm 2 and E a = 70–100 eV, two sharp emissions at 1.508 eV ( X 1) and 1.495 eV ( X 2), which have been attributed to the emissions of excitons bound to isolated N atoms, and another one at 1.443 eV ( X 5) were observed. These results show that nitrogen (N) atom in GaAs becomes optically active as an isoelectronic impurity at least in as-grown condition. For N + ion-irradiated samples with rather high I N, e.g., with I N = 75 nA/cm 2 and E a = 100 eV, a broad emission together with multiple sharp ones were observed after furnace annealing at 750°C which were ascribed to emissions of excitons bound to nitrogen-nitrogen (NN) pairs.