Thermal Excitation
Semiconductor materials produce free electrons and holes through the absorption of thermal energy without the influence of dopant atoms. This intrinsic carrier generation increases exponentially as the temperature of the silicon die rises. It sets the lower limit for the resistivity of the material in its pure state.
The effect is negligible at cryogenic temperatures but dominates the behavior of the sensor at high heat.
Lattice Vibration
Atoms in the crystal lattice vibrate more violently as they absorb thermal energy. During intrinsic carrier generation, these vibrations occasionally break a covalent bond to release a charge carrier. This mechanism is an inherent property of the atomic structure.
Leakage Current
These thermally created carriers contribute to a background current that flows even when no pressure is applied. In a sensor undergoing intrinsic carrier generation, the signal to noise ratio decreases as the operating temperature approaches the material limit. This current is often referred to as dark current in optical sensors.
Operating Temperature
Cooling the sensor reduces the number of carriers created by heat. Designers account for intrinsic carrier generation by setting a maximum rated temperature for the device. If this limit is exceeded, the semiconductor loses its ability to modulate current based on mechanical strain.
