Piezoresistance Effect in Germanium and Silicon

Giant piezoresistance in silicon-germanium alloys

“…The sensitivity of a piezoresistive sensor is determined by the strain gauge factor, given by G = 1 R dR d , where R is the resistance and the strain. The largest ambient temperature G found for single crystalline bulk silicon is G = 170, 3,5 and for germanium G = 100. 6 The state of the art material in the industry is poly-silicon, with G < 10, which can be improved to G 20 by using p-type poly-SiGe.…”

“…2 With improvements in the semiconductor electronics manufacturing processes, and the discovery in the 1950s that silicon and germanium have a very large piezoresistive effect, 3 the field of piezoresistive sensors started to flourish. Today, these sensors have a considerable market share of all microelectromechanical systems (MEMS)-based sensors, with applications that include strain gauges, accelerometers, pressure, force, and inertial sensors, atomic force microscopy, and even data storage.…”

Geometric and chemical components of the giant piezoresistance in silicon nanowires

“…Thus the stress will directly modify the free charge carrier density in the SiNW via a change in the interface trapped charge. This should be contrasted with the bulk PZR which is principally due to a change of the charge carrier mobility [2]. Although it is difficult to relate resistivity to a doping concentration (and hence a depletion layer width, W ) in SiNWs [28], the non-linear IV characteristic (inset, Fig.…”

“…In bulk crystalline silicon π depends on the crystal direction and doping type [2]. In the 110 direction of interest here π = π bulk = +71 × 10 −11 Pa −1 in p-Si and π = π bulk = −31 × 10 −11 Pa −1 in n-Si [2].…”

“…This effect, called piezoresistance (PZR), is well known in bulk crystalline silicon [2] and is widely exploited in order to improve the speed, gain and symmetry of modern CMOS microelectronic devices [3], as well as enabling silicon based MEMS sensor technologies [4]. Silicon nanowires (SiNW) have attracted attention for their PZR because of reports of giant or anomalous effects [5][6][7][8][9] that differ either in sign or magnitude from the bulk PZR.…”