Novel H⁺-Ion Sensor Based on a Gated Lateral BJT Pair

Area of Science:

• Materials Science
• Electrical Engineering
• Analytical Chemistry

Background:

• Classical ion-sensitive field-effect transistors (ISFETs) require bulky reference electrodes, complicating fabrication and integration.
• Existing ISFETs face challenges with miniaturization and integrated manufacturing due to reference electrode limitations.

Purpose of the Study:

• To propose and characterize a novel H⁺-ion sensor based on a gated lateral bipolar junction transistor (BJT) pair.
• To demonstrate an ISFET-type sensor that operates without a traditional external reference electrode.
• To explore a cost-effective alternative to current ISFET sensor technology.

Main Methods:

• Fabrication of a gated lateral BJT pair with one component featuring a silicide layer and the other without.
• Operation of the BJT pair in a metal-oxide semiconductor field-effect transistor (MOSFET)-BJT hybrid mode.
• Testing the sensor's response to buffer solutions of varying pH values.

Main Results:

• The proposed device simultaneously detected H⁺-ion concentration and acted as an internal reference due to differential sensitivities.
• Achieved a sensor sensitivity of approximately 0.175 μA/pH.
• Demonstrated successful operation without an external reference electrode.

Conclusions:

• The developed gated lateral BJT pair sensor offers a promising, electrode-free approach for H⁺-ion sensing.
• This technology has significant potential for reducing the manufacturing costs of ISFET-based sensors.
• The self-referencing capability enhances the practicality and applicability of the sensor.