Damage in InGaN/GaN bilayers upon Xe and Pb swift heavy ion irradiation

Area of Science:

• Materials Science
• Solid State Physics
• Ion Beam Physics

Background:

• Indium Gallium Nitride (InGaN) and Gallium Nitride (GaN) are critical materials for optoelectronic devices.
• Understanding their response to radiation is crucial for device reliability in harsh environments.
• Swift heavy ions (SHIs) can induce significant structural modifications in crystalline materials.

Purpose of the Study:

• To investigate the radiation effects of SHI bombardment on InGaN/GaN bilayers.
• To determine the susceptibility of InGaN and GaN to irradiation damage.
• To characterize the structural and elastic responses to SHI irradiation.

Main Methods:

• Irradiation of InGaN/GaN bilayers with xenon (Xe) and lead (Pb) ions at various energies and fluences.
• Analysis using Rutherford Backscattering Spectrometry in Channeling mode (RBS/C).
• Characterization via X-Ray Diffraction (XRD) and micro-Raman spectroscopy.
• Monte Carlo simulations (McChasy code) for damage assessment.

Main Results:

• InGaN exhibits higher susceptibility to irradiation damage compared to GaN.
• SHI bombardment leads to lattice expansion, primarily of the c-lattice parameter, indicating elastic response.
• Strain is observed even at low fluences, suggesting localized damage effects.
• Micro-Raman spectroscopy reveals a shift from dominant biaxial strain to combined hydrostatic and biaxial strain with increasing defect concentration.
• Simulations indicate the formation of randomly displaced atoms and dislocation loops.

Conclusions:

• The Poisson effect, caused by ion track pressure, is identified as the driving force for lattice expansion.
• SHI irradiation induces complex structural changes and strain in InGaN/GaN bilayers.
• The findings provide insights into the radiation hardness of nitride-based materials for potential applications exposed to energetic ions.