Abstract:
The incorporation of the Fluorine (F) ion into the Aluminum Gallium Nitride on Gallium Nitride (AlGaN/GaN) heterostructure has a significant application in the fabrication of the self-aligned enhancement-mode High Electron Mobility Transistors (HEMTs) devices. A series of positron beam measurements have been done in which the Variable Energy Doppler Broadening Spectroscopy (VEDBS) technique has been used for a systematic study on the AlGaN/GaN heterostructure.
VEDBS was used to probe defects in Fluorine implanted and Fluorine plasma injected Gallium Nitride (GaN) and Aluminum Gallium Nitride (Al0.25Ga0.75N) samples. Secondary Ion Mass Spectroscopy (SIMS) measurement and Stopping Range of Ion in Matter (SRIM) simulation were used to study the fluorine ion profile in GaN and AlGaN/GaN samples.
Group III vacancies (VGa and VAl) were formed when F ions were implanted into GaN and the AlGaN/GaN heterostructure. These kinds of group III vacancies diffuse towards the surface when annealed at low annealing temperature for GaN (400 °C and 600 °C) in N2 ambient. Vacancy clusters were found to form only with long annealing times (~72 hours).