Influence of neutron irradiation parameter and annealing temperature on neutron-transmutation-doped heteroepitaxial GaN film.

Neutron transmutation doping (NTD) has demonstrated its initial feasibility in offering precisely controlled and highly uniform dopants within bulk gallium nitride (GaN) wafers. This study aims to assess the doping efficacy of NTD applied to heteroepitaxial GaN films and address the technical challenges related to neutron damage and impurity activation through a comprehensive investigation of neutron irradiation parameters and annealing temperatures. Heteroepitaxial GaN films on sapphire were exposed to neutrons with varying thermal to fast neutron flux ratios in a fission reactor. The results highlight the successful application of the NTD process to heteroepitaxial GaN films, utilizing a relatively harder neutron spectrum with nearly equal thermal and fast neutron fluxes. Notably, a significant activation yield of 95.4 % was achieved through annealing at 1100 °C. Furthermore, the lattice damage and electrical conduction properties of heteroepitaxial GaN films show a strong correlation with the fast neutron fluence and annealing temperature. Elevated annealing temperature promotes the recovery from neutron-irradiated damage and enhances the activation of transmuted dopants. However, some residual defects still persist in neutron-irradiated GaN crystal after annealing. The outcomes of this study are expected to be useful for the establishment of optimal process parameters for NTD-GaN. [ABSTRACT FROM AUTHOR]