GaN and AlGaN/GaN heterostructures grown on two dimensional BN templates

Two dimension materials, like BN and graphene, have been shown to be excellent templates for the growth and fabrication of freestanding III-nitride materials. In this paper we study the effects of BN morphology on GaN and AlGaN/GaN heterostructures grown on these templates. The crystallinity, transport, and optical properties of the GaN layer are examined and found to be well correlated to the BN template. The self-separation of GaN from the BN/sapphire template is also connected to morphology, resulting in freestanding GaN layers. Transport properties of Si doped GaN and AlGaN/GaN heterostructures were examined for different BN templates. The bulk GaN mobility was closely linked to the morphology of the BN template resulting in room temperature mobility from 395 to 520 cm2/Vs. The range in 3D mobility can be linked to increased dislocation densities in GaN grown on rougher BN templates. High 2DEG mobility (~2000 cm2/Vs at 300 K) is achieved in AlGaN/GaN grown on atomically smooth BN templates, with a sheet electron density of 1×1013 cm−2, comparable to values obtained on conventional substrates. Samples grown on BN/sapphire showed mobilities (at 9 K) from ~33000 cm2/Vs to 15200 cm2/Vs depending on BN roughness. The differences are associated with variations in AlGaN/GaN interface-roughness scattering and dislocation density due to the BN template morphology.