Identification of As, Ge and Se Photoluminescence in GaN Using Radioactive Isotopes

Abstract

We report on experiments which unequivocal identify the chemical nature of optical transitions related to As (2.58 eV), Ge (3.398 eV) and Se (1.49 eV) found in the photoluminescence (PL) spectra of GaN. For this purpose epitaxial GaN layers were doped by ion implantation (60 keV, 3×1012 cm^-2) with the radioactive isotopes ⁷¹As and ⁷²Se. The isotope ⁷¹As (half-life 64.28 h) decays first into ⁷¹Ge (11.43 d), which finally transmutes into stable ⁷¹Ga. The isotope ⁷²Se decays via ⁷²As (26 h) into stable ⁷²Ge. These chemical transmutations were monitored with photoluminescence spectroscopy (PL). The half-lives resulting from exponential fits on our PL data are in excellent agreement with the half-lives of the isotopes. Our experiments clearly show that in each case the luminescence center involves exactly one As, Ge or Se atom. In addition to this, the results imply that no optically active GaN antisite exists.