BBr3 as a boron source in plasma-assisted molecular beam epitaxy

Abstract

Boron is a difficult material to use in a molecular beam epitaxy (MBE) reactor due to its high melting point as a pure compound. Consequently, there is interest in exploring alternative sources for B in MBE. In this paper, the authors detail the construction and operation of a novel BBr3 injection system for plasma-assisted MBE growth and show results for BGaN thin films grown using readily available low purity BBr3 as a proof of concept for the source. The BBr3 system enables the growth of coherent BGaN films with a concentration up to 3% B on the group III site and thicknesses up to 280 nm as determined by high resolution x-ray diffraction. Atom probe tomography and secondary ion mass spectroscopy results of a B0.03Ga0.97N film indicate a high level of Br impurity on the order of 1 × 1019 atoms/cm3 and atmospheric contamination consistent with a low purity source. BBr3 is successful as a B source for high crystal quality BGaN films; however, the Br incorporation from the source limits the applications for this material.