Photocurrent Measurement of PC and PV HgCdTe Detectors

Area of Science:

• Optoelectronics
• Detector Physics
• Metrology

Background:

• Maintaining accurate spectral responsivity scales is crucial for infrared detector characterization.
• Standard photoconductive (PC) and photovoltaic (PV) HgCdTe detectors require specialized preamplifiers for reliable measurements.
• Existing preamplifiers may introduce noise or require compensation, impacting measurement accuracy.

Purpose of the Study:

• To develop novel preamplifiers for HgCdTe detectors operating in PC and PV modes.
• To ensure the maintenance of the spectral responsivity scale of the National Institute of Standards and Technology (NIST) in the 5 μm to 20 μm range.
• To optimize signal-to-noise ratio and minimize uncertainties in photocurrent measurements.

Main Methods:

• Designed a linear PC mode preamplifier that eliminates the need for detector bias current compensation.
• Utilized impedance multiplication with a positive feedback buffer amplifier in a bootstrap PV transimpedance amplifier.
• Analyzed gain equations and calculated signal gain errors for PC and PV preamplifiers.
• Investigated and optimized signal-to-noise ratios and noise/drift performance.

Main Results:

• Developed PC preamplifiers that do not require compensating sources.
• Achieved a maximum signal gain of 10(8) V/A for the PV transimpedance amplifier measuring a 200 Ω shunt resistance photodiode.
• Identified optimal signal frequency ranges for low-uncertainty photocurrent-to-voltage conversion.
• Presented measurement results on signal ranges and noise performance.

Conclusions:

• The developed preamplifiers effectively maintain the spectral responsivity scale for HgCdTe detectors.
• The novel designs offer improved performance in both PC and PV modes, crucial for metrology applications.
• The study provides essential gain equations and performance data for future detector preamplifier design.