Bow-Tie Microwave Diodes on the Base of Modulation-Doped Semiconductor Structure with Wide Spacer: Theory and Experiment

Bow-tie microwave diodes have proven to be effective sensors of electromagnetic radiation across a wide wavelength range, from centimeter-scale radio waves to micrometer-scale mid-infrared radiation. Their operation is based on electron heating by strong electric fields. However, the experimental data obtained so far remain inconclusive, and the exact nature of the voltage detected by bow-tie diodes is not yet fully understood. In this work, we extend the investigation of the electrical properties of bow-tie diodes based on modulation-doped semiconductor structures with a wide spacer. The analysis focuses on the influence of diode metal contact geometry, illumination conditions, and orientation relative to the crystallographic axes. To elucidate the origin of the voltage detected by bow-tie diodes, we compare theoretical predictions of their electrical parameters—including voltage sensitivity, electrical resistance, asymmetry of the I–V characteristic in weak electric fields, and the nonlinearity coefficient of the I–V characteristic in strong electric fields—with corresponding experimental results. The results of our investigations indicate that, for most diodes, the detected voltage originates from electron heating by the microwave electric field, as evidenced by the polarity of the detected voltage matching the thermoelectric emf of hot carriers.