Depth-dependent EBIC microscopy of radial-junction Si micropillar arrays

Area of Science:

• Semiconductor device physics
• Materials science and engineering
• Optoelectronics

Background:

• Radial-junction architectures offer advantages over planar designs for optoelectronic devices.
• Three-dimensional (3D) structures maximize optical interaction and carrier extraction.
• Fabrication advances enable cost-effective and high-performance radial-junction devices.

Purpose of the Study:

• To characterize radial PN junctions fabricated using silicon micropillars and phosphorus diffusion.
• To evaluate the carrier separation and collection efficiency of these 3D junctions.
• To assess the suitability of electron-beam induced current (EBIC) microscopy for analyzing micro/nanostructured semiconductors.

Main Methods:

• Fabrication of p-type silicon micropillars via deep reactive-ion etching (DRIE).
• Formation of an n-type layer through phosphorus gas diffusion.
• Characterization using electron-beam induced current (EBIC) microscopy.
• Analysis using Monte-Carlo simulations and EBIC modeling.

Main Results:

• Uniform PN junctions were conformally constructed on the 3D pillar array.
• EBIC efficiency increased with incident electron beam energy, consistent with planar devices.
• The radial-junction pillar array achieved approximately 70% EBIC efficiency at 10 kV, slightly lower than planar devices (≈ 81%).

Conclusions:

• The depth-dependent EBIC approach is suitable for evaluating PN junctions in micro/nanostructured semiconductors.
• Reduced efficiency in radial junctions may stem from unpassivated surfaces and DRIE-induced defects.
• Radial-junction architectures show promise for advanced optoelectronic applications.