Anisotropic low-temperature piezoresistance in (311)A GaAs two-dimensional holes

The authors report low-temperature resistance measurements in a modulation-doped, (311) A GaAs two-dimensional hole system as a function of applied in-plane strain. The data reveal a strong but anisotropic piezoresistance whose magnitude depends on the density as well as the direction along which the resistance is measured. At a density of 1.6 X 10(11) cm(-2) and for a strain of about 2 X 10(-4) applied along the [01(1) over bar], e. g., the resistance measured along this direction changes by nearly a factor of 2, while the resistance change in the [(2) over bar 33] direction is less than 10% and has the opposite sign. The accurate energy band calculations indicate a pronounced and anisotropic deformation of the heavy-hole dispersion with strain, qualitatively consistent with the experimental data. The extremely anisotropic magnitude of the piezoresistance, however, lacks a quantitative explanation. (c) 2007 American Institute of Physics.