Dopant activation process in Mg-implanted GaN studied by monoenergetic positron beam

Area of Science:

• Materials Science
• Semiconductor Physics
• Defect Engineering

Background:

• Magnesium (Mg)-implanted Gallium Nitride (GaN) is a key material for optoelectronic devices.
• Understanding Mg activation and its relationship with defects is critical for device performance.
• Positron annihilation spectroscopy (PAS) is a sensitive technique for studying vacancy-type defects.

Purpose of the Study:

• To investigate the process of Mg activation in GaN.
• To elucidate the relationship between Mg activation and vacancy-type defects.
• To determine the role of sequential nitrogen (N) implantation in enhancing Mg activation.

Main Methods:

• Mg+ and N+ ions were implanted into GaN at specific energies and concentrations.
• Capacitance-voltage (C-V) measurements were used to assess Mg activation.
• Positron annihilation spectroscopy (PAS) was employed to identify and quantify vacancy-type defects.
• Annealing studies were performed at various temperatures (below 1000 °C and above 1200 °C).

Main Results:

• Sequential N implantation significantly enhanced Mg activation in GaN.
• Before annealing, Ga-vacancy related defects, such as divacancies, were the primary defect species.
• Annealing below 1000 °C led to vacancy clustering.
• Annealing above 1200 °C resulted in a decrease in vacancy size due to recombination with excess N atoms.
• N implantation suppressed vacancy clustering.

Conclusions:

• The suppression of vacancy clustering by sequential N implantation is the primary reason for the enhanced Mg activation in Mg-implanted GaN.
• This finding provides a pathway for optimizing the electrical properties of Mg-doped GaN through defect engineering.