Nuclear reaction analysis of carbon-doped GaN: the interstitial carbon as an origin of yellow luminescence

Nuclear reaction analysis (NRA), using the 12C(d, p)13C and 14N(d, p)15N reactions, in conjunction with Rutherford backscattering spectrometry (RBS) in the channeling geometry is used to evaluate the substitutional fractions of C and N in 〈0001〉-oriented GaN intentionally doped by a gas phase doping at 1000 °C for 3 h under C2H6-gas flow to a C concentration of ∼3.7×1020 cm−3. The C doped samples show the intense photoluminescence at ∼2.2 eV, so-called the yellow luminescence (YL). From NRA, ∼74% for C atoms and ∼7.5% for N atoms are displaced from their lattice sites, respectively. The displacement of Ga atoms cannot seen from the angular scan of the RBS channeling so that it is evident that the Ga vacancies are not introduced by the gas phase doping. These results suggest the existence of the interstitial C and the displacement of nearby N atoms. This strongly supports a mechanism of the YL attributing to the interstitial carbon and/or its complex defects.