We report on the room-temperature electrical rectification at 1.5 THz of a unipolar nanodiode based on symmetry breaking in a nanochannel. The exploitation of its nonlinear diodelike characteristic and intrinsically low parasitic capacitance enables rectification at ultrahigh speed. The zero-voltage threshold and unique planar layout make the nanodiode suitable for building large arrays. This is the highest speed reported in nanorectifiers to date.

Unipolar nanodiodes, also known as self-switching devices, have recently been demonstrated as terahertz detectors at room temperature. Here, we study their low-frequency noise spectra and noise equivalent power and show that both performance parameters are comparable to those reported for state-of-the-art Schottky diodes. The truly planar nanodiode layout enables building structures with thousands of devices connected in parallel, which reduce low-frequency noise without affecting sensitivity. The observed 1/f noise can be described by Hooge's mobility fluctuation theory.

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Self-switching diode (SSD) is a unipolar two-terminal planar device which has a typical channel in nanoscale dimension. It has shown outstanding properties as a microwave and submillimeter wave rectifier by exploiting its nonlinear current-voltage (I-V) characteristic and intrisically low parasitic capacitance. In detection systems, SSDs are often used with an antenna to form a rectifying antenna (rectenna). The large impedance mismatch between SSD and antenna, due to high resistance of a single SSD, has always hampered the rectenna to achieve good extrinsic rectification performance (e.g., voltage responsivity > 400 V/W). As such, a large array of SSDs connected in parallel is very much desired to reduce the device resistance, and hence minimizing the impedance mismatching issue. In this work, an interdigital structure which can accommodate approximately 2,000 SSDs in parallel has been utilized. The material used was InGaAs/InAlAs heterostructure grown onto an InP substrate. The fabrication of the SSD array has implemented an electron-beam lithography (EBL) technique and the use of polymethyl methacrylate (PMMA) as a masking layer. The fabricated SSD array has shown a typical diode-like I-V characteristic, indicating that EBL method is not only convenient to realize nanoscale electronic devices, but also very practical for large area operations.