Defect Analysis in a Long-Wave Infrared HgCdTe Auger-Suppressed Photodiode

Area of Science:

• Semiconductor Physics
• Materials Science
• Optoelectronics

Background:

• HgCdTe heterostructures are crucial for long-wave infrared (LWIR) photodiode applications.
• Understanding deep defects is essential for optimizing photodiode performance and reducing dark currents.

Purpose of the Study:

• To characterize deep defects in LWIR HgCdTe photodiodes.
• To identify the specific defects responsible for increased dark currents.
• To determine the physical parameters of these defects.

Main Methods:

• Metal-organic chemical vapor deposition (MOCVD) for photodiode fabrication.
• Deep-level transient spectroscopy (DLTS) for defect energy level and concentration measurements.
• Photoluminescence (PL) spectroscopy for defect verification and energy level determination.

Main Results:

• Two defects were identified: an electron trap (252 meV) and a hole trap (89 meV).
• The hole trap, attributed to mercury vacancies (VHg), was found to be the main contributor to dark current.
• Specific parameters for the VHg trap were determined: capture cross-section (σ = 10⁻¹⁶–4 × 10⁻¹⁵ cm²) and concentration (N = 3–4 × 10¹⁴ cm⁻³).

Conclusions:

• Mercury vacancies (VHg) are a significant defect in LWIR HgCdTe photodiodes.
• VHg defects directly increase dark currents, impacting device performance.
• The detailed characterization provides critical data for mitigating dark current in future HgCdTe photodiode designs.