We present our studies on fabrication and electrical and optical characterization of
semiconducting asymmetric nanochannel diodes (ANCDs), focusing mainly on the temperature dependence of their current–voltage (I–V) characteristics in the range from room temperature to
77 K. These measurements enable us to elucidate the electron transport mechanism in a nanochannel. Our test devices were fabricated in a GaAs/AlGaAs heterostructure with a twodimensional
electron gas layer and were patterned using electron-beam lithography. The 250-nmwide, 70-nm-deep trenches that define the nanochannel were ion-beam etched using the photoresist as a mask, so the resulting nanostructure consisted of approximately ten ANCDs
connected in parallel with 2-μm-long, 230-nm-wide nanochannels. The ANCD I–V curves
collected in the dark exhibited nonlinear, diode-type behavior at all tested temperatures. Their
forward-biased regions were fitted to the classical diode equation with a thermionic barrier, with the ideality factor n and the saturation current as fitting parameters. We have obtained very good
fits, but with n as large as ~50, suggesting that there must be a substantial voltage drop likely at
the contact pads. The thermionic energy barrier was determined to be 56 meV at high temperatures. We have also observed that under optical illumination our ANCDs at low temperatures exhibited, at low illumination powers, a very strong photoresponse enhancement that exceeded that at room temperature. At 78 K, the responsivity was of the order of 104 A/W at the nW-level light excitation
