Physical Phenomenon
Physical phenomenon where the electrical resistivity of a boron-doped semiconductor changes in response to applied mechanical strain. Utilizing p-type silicon piezoresistance allows for the creation of highly sensitive pressure transducers and accelerometers. The effect is much stronger in semiconductors than in traditional metal foil strain gauges.
This enables the detection of extremely small pressure changes that would otherwise be lost in the noise floor of less sensitive materials.
Crystal Orientation
Magnitude of the effect depends on the direction of the stress relative to the crystal lattice. Most devices utilizing p-type silicon piezoresistance align the sensing elements along the (110) direction of the wafer. This orientation maximizes the longitudinal piezoresistive coefficient.
Thermal Sensitivity
Resistance and the strain sensitivity both vary with ambient temperature. The p-type silicon piezoresistance effect becomes less pronounced as the temperature rises. Sophisticated compensation algorithms or hardware bridges are necessary to maintain accuracy over a wide thermal window.
Metrological Limit
Linearity holds well at low strain levels but degrades as the stress approaches the fracture limit of the crystal. Measurements of p-type silicon piezoresistance are calibrated against a known displacement or force. This calibration accounts for the non-linear behaviour at the extremes of the measurement range.
