Boron lattice site location in (BGa)As and (BGa)P thin films studied using RBS and NRA with a channeled He+ ion beam

In this study the boron lattice site location in ternary BxGa1-xAs and BxGa1-xP thin films grown on (0 0 1) GaAs and (0 0 1) GaP, respectively, using low pressure metal-organic vapour-phase epitaxy (MOVPE) with boron concentrations between x = 0.8% and x = 3.2% was investigated with RBS and the 10B(α,p)13C nuclear reaction using a 2.3 MeV He+ ion beam. For this purpose, the ion beam was aligned with the [0 0 1], [0 1 1] and [1 1 1] axis and the RBS and proton yield from the nuclear reaction compared with random ion incidence. For comparison, theoretical proton yields which assume boron to be located on substitutional lattice sites only were calculated for each sample/axis combination and compared with the experimental yields. The RBS/channeling measurements show a very good crystal quality of the films with χmin being in the range of 3-5% for the [0 1 1] axis. The best crystal qualities, i.e. the lowest χmin values and dechanneling rates, are achieved for low boron concentrations. From NRA/channeling it can be deduced that in the BxGa1-xAs films the fraction of interstitial boron is approximately 5% for low boron concentrations of x = 1% and 6-10% for concentrations up to x = 3.2%, whereas the fraction of interstitial boron is less than 3% in the BxGa1-xP film studied despite a concentration of x = 2.0%. This indicates that antisite effects of the boron incorporation are more likely in GaAs compared to GaP.