Evaluation of lattice displacement in Mg – Implanted GaN by Rutherford backscattering spectroscopy

Abstract

Evaluation of lattice displacement in Mg-ion implanted GaN is studied by combining elastic recoil detection analysis (ERDA), Rutherford backscattering spectroscopy (RBS) and Photoluminescence (PL) measurements. Mg-ion implantation into GaN single crystal wafer is performed with energies of 30keV (ion fluence; 3.5×1014cm−2) and 60keV (6.5×1014cm−2) at room temperature. The ERDA measurements using the 1.5MeV helium beam can evaluate hydrogen from the surface to ∼300nm. The hydrogen concentration for un-implanted and as-implanted GaN is 3.1×1014cm−2 and 6.1×1014cm−2 at around 265nm in depth. χmin (the ratio of aligned and random yields) near the surface of the 〈0001〉 direction for Ga is 1.61% for un-implanted and 2.51% for Mg-ion implanted samples. On the other hand, the value of χmin for N is 10.08% for un-implanted and 11.20% for Mg-ion implanted samples. The displacement concentration of Ga and N estimated from these χmin values is 4.01×1020cm−3 and 5.46×1020cm−3, respectively. This suggests that Ga vacancy (VGa), N vacancy (VN), Ga interstitial (Gai), and N interstitial (Ni) is introduced in Mg-ion implanted GaN. A strong emission at around 400nm in as-implanted GaN is related to a VN donor and some acceptor pairs. It is suggested that the origin of the very high resistivity after the Mg-ion implantation is attributed to the carrier compensation effect due to the deep level of Ni as a non-radiative center.