Structure and luminescence of a-plane GaN on r-plane sapphire substrate modified by Si implantation* *Project supported by the Key-Area Research and Development Program of Guangdong Province, China (Grant Nos. 2019B010132001, 2020B010174003, and 2019B121204004), the Basic and Application Basic Research Foundation of Guangdong Province, China (Grant Nos. 2020A1515110891 and 2019A1515111053), and the Fund from the Ion Beam Center (IBC) at HZDR.

Abstract

We show the structural and optical properties of non-polar a-plane GaN epitaxial films modified by Si ion implantation. Upon gradually raising Si fluences from 5 × 1013 cm−2 to 5 × 1015 cm−2, the n-type dopant concentration gradually increases from 4.6 × 1018 cm−2 to 4.5 × 1020 cm−2, while the generated vacancy density accordingly raises from 3.7 × 1013 cm−2 to 3.8 × 1015 cm−2. Moreover, despite that the implantation enhances structural disorder, the epitaxial structure of the implanted region is still well preserved which is confirmed by Rutherford backscattering channeling spectrometry measurements. The monotonical uniaxial lattice expansion along the a direction (out-of-plane direction) is observed as a function of fluences till 1 × 1015 cm−2, which ceases at the overdose of 5 × 1015 cm−2 due to the partial amorphization in the surface region. Upon raising irradiation dose, a yellow emission in the as-grown sample is gradually quenched, probably due to the irradiation-induced generation of non-radiative recombination centers.