Multistage ballistic rectifiers on Si/SiGe hetreostructures

• Applicant: Professor Dr. Joachim Knoch, since 7/2021
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2018 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397194044

Multistage ballistic rectifiers are prepared on modulation-doped Si/SiGe heterostructures. Their single stages consist of asymmetric nanoscale cross junctions, which exhibit a parabolic output-voltage-vs-input-current characteristic. Accordingly, the polarity of the output voltage is independent of that of the input current. The mechanism of this full-wave rectification relies upon a stationary charging of the current-free voltage channel over the distance of the momentum relaxation length (MRL), if the MRL is larger than the lateral dimension of the cross junction. Since the output voltage of a single stage only reaches a few mV, many rectifier stages are necessary for technical applications. In the present project, we exploit the recently published effect of input-current addition, which arises if the stage separation is smaller than the MRL, and which in dual-stage rectifiers causes a synergy gain in the output voltage of a factor of two due to the parabolic transfer characteristic. Therefore, the rectifier stages are positioned as close as possible. At first, the rectifier efficiency of the single stages is determined at low temperatures by measurements in the nonlinear transport regime. As assumed from studying densely positioned dual-stage ballistic rectifiers, the efficiency of the single rectifier stages is worsened by mutual disturbing of the potential landscape defining the asymmetric cross junctions. This problem is to be solved as far as possible by an improved geometry. Accordingly optimized multiple-stage rectifiers are studied regarding their current-addition effects in a temperature range from 4 K to 120 K. Finally, the number of stages will be determined which is necessary to achieve an output voltage approaching the input voltage. Appropriately prepared multi-stage rectifiers will be characterised with respect to parameters which are relevant for their use as technical device.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Ulrich Kunze, until 6/2021