Narrowband Deep UV Sensor on CVD-Grown Diamond Epilayers.

Area of Science:

• Optoelectronics
• Materials Science
• Solid-State Physics

Background:

• Technological applications like encrypted communication and environmental monitoring necessitate precise wavelength detection.
• Conventional broadband photodetectors (PDs) often require external wavelength filters, adding complexity and cost.
• Advancements in detecting specific wavelengths enhance system security, efficiency, and accuracy.

Purpose of the Study:

• To introduce a thermally resilient metal-semiconductor-metal deep UV photodetector (MSM DUV PD) fabricated on chemical vapor deposition (CVD)-grown diamond.
• To demonstrate the device's capability as a narrowband PD in the deep UV (DUV) range.
• To investigate the underlying mechanisms responsible for the narrowband detection and assess performance at elevated temperatures.

Main Methods:

• Fabrication of an MSM DUV PD on CVD-grown diamond.
• Characterization of spectral response, responsivity, and full width at half maximum (FWHM).
• Evaluation of device performance, including dark current, detectivity, noise equivalent power, and response time, at temperatures up to 423 K.
• Analysis of cathodoluminescence and photoluminescence properties of diamond to understand detection mechanisms.

Main Results:

• The fabricated MSM DUV PD exhibited narrowband detection in the DUV region with an FWHM of 14.4 nm and peak responsivity at 210 nm under a 5 V bias.
• Narrowband detection functionality was maintained at elevated temperatures up to 423 K.
• Radiative and nonradiative recombination via trap energy states in the diamond's bandgap were identified as the cause of narrowband detection.
• The device demonstrated a low dark current (10⁻¹⁴ A), high detectivity (2.64 × 10¹¹ Jones), low noise equivalent power (1.4 × 10⁻¹³ W/Hz¹/²), and a response time of 0.8 s.
• Self-biased operational mode was observed.

Conclusions:

• CVD-grown diamond is a promising material for fabricating thermally resilient, narrowband DUV photodetectors.
• The developed MSM DUV PD offers advantages over conventional broadband PDs by eliminating the need for external filters.
• The device's performance characteristics, including high detectivity and low dark current, make it suitable for detecting weak signals in noisy environments.
• Understanding the role of trap states in recombination is crucial for optimizing future DUV photodetector designs.