Atom probe tomography study of Mg-doped GaN layers

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Research

Background:

• Gallium Nitride (GaN) is a key material for optoelectronic devices.
• Understanding dopant behavior, such as Magnesium (Mg) in GaN, is crucial for device performance.
• Stacking faults (SFs) in GaN can impact optical properties, but their behavior in highly doped material is not fully understood.

Purpose of the Study:

• To investigate the effect of high Magnesium doping concentrations on the microstructure and optical properties of homoepitaxial GaN (0001) layers.
• To determine the relationship between Mg distribution, cluster formation, and the optical activity of stacking faults.

Main Methods:

• Atom probe tomography (APT) was employed to analyze the three-dimensional distribution of Mg atoms in GaN.
• Cathodoluminescence (CL) spectroscopy was used to study the optical emission properties of the GaN layers.

Main Results:

• Mg cluster formation was observed exclusively in GaN layers doped at 1 × 10(20) cm(-3).
• Lower doped GaN layers (∼5 × 10(19) cm(-3)) exhibited homogeneous Mg distribution and displayed emission attributed to stacking faults.
• The stacking fault emission was absent in the higher doped layer where Mg clusters were present.

Conclusions:

• Mg clusters in highly doped GaN are proposed to induce a screening effect.
• This screening effect is hypothesized to disrupt the exciton binding to stacking faults.
• Consequently, Mg clusters render stacking faults optically inactive in highly doped GaN.