Laser damage mechanisms in conductive widegap semiconductor films

Area of Science:

• Materials Science
• Semiconductor Physics
• Laser-Material Interactions

Background:

• Conductive wide-bandgap semiconductors like Indium Tin Oxide (ITO) and Silicon-doped Gallium Nitride (Si:GaN) are crucial for optoelectronic applications.
• Understanding their laser damage mechanisms is vital for device reliability and performance.
• Previous studies often focused on laser photon energies exceeding the bandgap, limiting insights into sub-bandgap interactions.

Purpose of the Study:

• To investigate and compare the laser damage mechanisms of ITO and Si:GaN films under nanosecond pulsed laser irradiation.
• To elucidate the distinct damage morphologies and underlying physical processes in these two conductive semiconductor films.
• To explore the role of free carrier absorption and potential defect markers in laser-induced damage.

Main Methods:

• Microscopy (e.g., optical, electron microscopy) for morphological analysis.
• Spectroscopy (e.g., optical, Raman) for chemical and electronic state characterization.
• Photoluminescence (PL) spectroscopy to probe electronic transitions and defect states.
• Elemental analysis (e.g., EDX) to determine film composition.
• Controlled nanosecond laser pulse exposure with photon energy below the film bandgaps (1.03 eV, 1064 nm).

Main Results:

• Indium Tin Oxide (ITO) films displayed deterministic features indicative of thermal degradation.
• Silicon-doped Gallium Nitride (Si:GaN) films exhibited highly localized damage, manifesting as eruptions originating at internal interfaces.
• Thermally driven damage in ITO was correlated with free carrier absorption.
• Carbon complexes were identified as potential precursors or markers for laser damage in Si:GaN.

Conclusions:

• Laser-induced damage mechanisms in ITO and Si:GaN differ significantly, even under sub-bandgap irradiation.
• Thermal degradation via free carrier absorption dominates ITO laser damage.
• Interface-related phenomena and potential defect markers like carbon complexes are critical in Si:GaN laser damage.
• These findings provide crucial insights for the design and application of wide-bandgap semiconductor devices subjected to laser exposure.