Selective thermal neutron transmutation doping with Gd masks in GaN semiconductors

For the first time, selective neutron transmutation doping was successfully performed on GaN through Gd masks, showing the feasibility of patternable doping through neutron irradiations. In collaborating with Oak Ridge National Laboratory, GaN with Gd masks was irradiated by directional neutrons. By using the Gd properties with high neutron absorption cross-sections, it was confirmed that the area covered by Gd masks on GaN was completely shielded from neutron, and the uncovered area was doped with the generated Ge and ¹⁴C. The difference was clearly identified in various ways when comparing the area exposed by neutrons and the area unexposed by neutrons. The discoloration by the ejected protons and elastic scattering of neutrons appeared only in the exposed area, and the unexposed area was the same as before irradiation. The neutron scattering angle in GaN was estimated by comparing the front and backside. From energy dispersive X-ray spectroscopy spectra and secondary ion mass spectrometry measurement, the concentration difference as well as the exact concentration of produced ¹⁴C was also checked. Schottky barrier diodes on the selectively doped GaN were fabricated and investigated to study the electrical properties.