Novel Semiconductor Nanodevices for Detections of THz Signals

By introducing a broken geometric symmetry in a semiconductor nanochannel, we have realized an array of planar nano-diodes, called a self-switching device (SSD), using only one nanolithography step. Not only being much simpler than conventional diodes which generally require a multi-layer architecture and multi-step lithography, the SSD also possesses a very high operational speed because of the simplicity and hence a low parasitic capacitance. A stable detection sensitivity up to 110 GHz was demonstrated at room temperature. This is, to the best of our knowledge, the highest speed that has been reported in various types of novel electronic nanodevices to date. The novel working principle enabled the SSD to detect microwaves without a DC bias. We show that the planar architecture allows for an arbitrary number of SSDs to be connected in parallel by folding a linear array as many times as required over a large area. This reduces the total impedance and more importantly enables a low detection noise because the fluctuations in individual SSDs are averaged out. Although only about one percent of the RF power was effectively applied to an array of 18 parallel SSDs due to the impedance mismatch, our experiment showed a sensitivity of approximately 120 mV DC output for every mW of nominal microwave input. In another array consisting of 45 SSDs, the sensitivity reached more than 800 mV/mW, which is about twice of that of a standard microwave diode detector