Characterization of the anomalous giant piezoresistance in AlAs two-dimensional electrons with anti-dot lattices

We report the characterization of a giant piezoresistance effect observed in a two-valley, two-dimensional electron system confined to an AlAs quantum well and patterned with anti-dot lattices of ∼1 μm period. The system exhibits a low-temperature piezoresistive gauge factor (the fractional change in resistance divided by the fractional change in the sample's length), which depends on the anti-dot lattice period and can be as high as 22 000. Via monitoring the resistance of a simple, 40 μm long Hall bar sample based on this system, we are readily able to measure strain values down to 10 ^-8 or, equivalently, length changes of the order of 1/100 of the Bohr radius.