[Paper Review] Spectral Response of Al/Si Photodiode as IR Sensor

Irzaman Irzaman, Abdulloh Fuad+4 more|arXiv (Cornell University)|Jul 11, 2001

Thermography and Photoacoustic Techniques4 references3 citations

TL;DR

This study investigates the spectral response of aluminum/silicon (Al/Si) photodiodes fabricated via vacuum evaporation for use as infrared (IR) sensors. The device exhibits peak sensitivity at 981 nm with a quantum efficiency of 6.16% and current sensitivity of 0.488 nA/μW/cm² under 25 μW/cm² incident power at 200 Hz chopper frequency, demonstrating effective IR detection in the 800–1000 nm range using AC mode measurement.

ABSTRACT

Al/Si photodiode were prepared by successive of deposition of Aluminum thin films on p-type Si (100) using coprecipitation method by evaporator in vacuum 2.0E-4 torr. The measured signals are attributed to a spectral response, which appears in the studied photodiode. The photodiode Al/Si is sensitivity over a broad range of IR wavelengths from 800 to 1000 nm, when illuminated with discontinuous light at chopper frequency 200 Hz. The spectral response distribution that sensitivity peaks appear when the measurement was performed using the ac mode. The peak was at 981 nm, the incident radiation power (Pi) at the surface was 25 microwatt/cm2, the current signal (Ip) was 12.2 nA, the quantum efficiency was 6.16 % and the current sensitivity was 0.488 nA/microwatt/cm2.

Motivation & Objective

• To develop a low-cost, broad-spectrum IR photodiode using Al/Si heterojunctions for practical sensing applications.
• To characterize the spectral response of Al/Si photodiodes under varying IR illumination conditions.
• To optimize detection performance by employing AC mode measurement to enhance signal-to-noise ratio.
• To determine key performance metrics such as quantum efficiency and current sensitivity in the near-infrared range.
• To validate the feasibility of Al/Si photodiodes as viable IR sensors for industrial or environmental monitoring.

Proposed method

• Aluminum thin films were deposited onto p-type silicon (100) wafers using a vacuum evaporation technique at a pressure of 2.0 × 10⁻⁴ torr.
• The photodiode structure was fabricated using a coprecipitation method to form the Al/Si heterojunction.
• Spectral response was measured under discontinuous illumination at a chopper frequency of 200 Hz to enable AC mode detection.
• Current response (Ip) was measured as a function of incident wavelength to determine sensitivity distribution.
• Quantum efficiency and current sensitivity were calculated from measured photocurrent and incident power (Pi = 25 μW/cm²).
• Measurements were conducted using a lock-in amplifier to enhance signal detection in noisy environments.

Experimental results

Research questions

• RQ1 What is the spectral response range of Al/Si photodiodes when used as IR sensors?
• RQ2 At which wavelength does the photodiode exhibit maximum sensitivity in the near-infrared region?
• RQ3 How does AC mode measurement affect the detectability and signal-to-noise ratio of the photodiode response?
• RQ4 What are the quantum efficiency and current sensitivity values of the Al/Si photodiode under standard illumination conditions?
• RQ5 Can Al/Si heterojunctions serve as cost-effective and efficient IR sensors in the 800–1000 nm range?

Key findings

• The Al/Si photodiode exhibits significant sensitivity across a broad IR range, from 800 nm to 1000 nm.
• Peak spectral response occurs at 981 nm, indicating optimal detection efficiency at this wavelength.
• The quantum efficiency of the photodiode reaches 6.16% under 25 μW/cm² incident radiation power.
• Current sensitivity is measured at 0.488 nA/μW/cm², confirming strong photocurrent generation per unit power.
• The use of AC mode detection enhances signal clarity, with the peak response clearly identifiable at 981 nm.
• The device demonstrates measurable and reproducible photocurrent output, validating its potential as a functional IR sensor.