The giant piezoresistance (PZR) previously reported in silicon nanowires is experimentally investigated in a large number of surface depleted silicon nano- and micro-structures. The resistance is shown to vary strongly with time due to electron and h
ole trapping at the sample surfaces. Importantly, this time varying resistance manifests itself as an apparent giant PZR identical to that reported elsewhere. By modulating the applied stress in time, the true PZR of the structures is found to be comparable with that of bulk silicon.
The tunnel photocurrent between a gold surface and a free-standing semiconducting thin film excited from the rear by above bandgap light has been measured as a function of applied bias, tunnel distance and excitation light power. The results are comp
ared with the predictions of a model which includes the bias dependence of the tunnel barrier height and the bias-induced decrease of surface recombination velocity. It is found that i) the tunnel photocurrent from the conduction band dominates that from surface states. ii) At large tunnel distance the exponential bias dependence of the current is explained by that of the tunnel barrier height, while at small distance the change of surface recombination velocity is dominant.
