Voltage and Current Excitation from Acoustically Stimulated Band Gap Modulation in InSb

Some semiconductors have energy band gaps that depend on mechanical pressure. We theorize that a gradient in the band gap occurs when an acoustic pressure gradient is present in these materials, and that carrier density gradients develop and produce diffusion current if the electron and hole mobilities differ. The electrical response depends on temperature and the magnitude of difference between electron and hole mobilities. Experiments have shown that a pressure gradient causes a gradient in carrier density in indium antimonide (InSb). The energy band gap of InSb increases with pressure, and carrier densities decrease. A standing acoustic wave in InSb modulates a pressure-induced variable band gap and corresponding carrier density gradients which leads to a dynamic diffusion current and internal electric field. Open-circuit voltage and closed-circuit current are predicted to be in mV and tenths of mA ranges for an intrinsic InSb bar at room temperature with dimensions of 13.7 mm by 5 mm by 3mm, and hosting a longitudinal standing acoustic wave at a frequency of 230 kHz and with amplitude of 2.23 MPa (rms). Acoustically driven electrical responses fluctuate on the same time and spatial scales as the acoustic wave, and it is shown electron transport may be treated as quasi-static.