Junction Formation and Leakage Current Suppression in Planar High-Purity Germanium Detectors for Low-Energy X-Ray...

Area of Science:

• Semiconductor Physics
• Materials Science
• Detector Technology

Background:

• Planar high-purity germanium (HPGe) detectors require improved dark-current control for sensitive low-energy X-ray detection.
• Existing fabrication methods often overlook interconnected processing routes for surface treatment, junction formation, and leakage current regulation.

Purpose of the Study:

• To develop an integrated device fabrication strategy for planar HPGe detectors.
• To optimize near-surface treatment, N/P junction formation, and guard-ring electrode design.
• To achieve low dark current and stable current response for low-energy X-ray detection.

Main Methods:

• Chemical mechanical polishing (CMP) to reduce surface roughness.
• Optimized lithium (Li) thermal diffusion for N-type contact layer formation.
• Boron (B) ion implantation and rapid thermal processing (RTP) for P-type junction fabrication.
• Guard-ring electrode implementation.
• Geant4 simulations for response analysis.

Main Results:

• CMP reduced HPGe surface roughness (Sa) to 6.68 nm.
• Optimized Li diffusion and B implantation yielded favorable electrical and structural properties.
• Guard-ring electrode reduced dark current from 6.5 × 10^-9 A to 2.03 × 10^-9 A at -20 V.
• Stable switching current response achieved under 12 keV X-ray irradiation.

Conclusions:

• The interconnected processing route effectively minimizes dark current and enhances response stability in planar HPGe detectors.
• Optimized fabrication processes provide a foundation for advanced low-energy X-ray detection applications.
• The study validates the effectiveness of guard-ring electrodes in improving detector performance.