Metal-insulator-metal tunneling diode for uncooled infrared high-speed detectors

A metal-insulator-metal (MIM) tunneling diode having response time less than a picosecond (10(-12) second) is extremely important for mixers and detectors operating at terahertz and infrared frequencies. One of the key objectives of this work is to develop fabrication processes which are well-suited for mass production of nanogap MIM tunneling diodes with junction area in the range of 10(-2) mu m(2) thus enabling the coveted terahertz frequencies due to the greatly reduced junction capacitance. A contemporary electron beam stepper of such resolution costs tens of millions and is not viable for mass production. This work employs standard photolithography and atomic layer deposition (ALD) methods, which allow formation of a micrometer-wide finger in the second metal layer that is separated from the first layer metal electrode by an ALD-deposited sidewall dielectric spacer, thus forming a nm-thick vertical tunneling junction. The junction area is defined by the width of the finger and the thickness of the electrode, while the junction thickness is controlled by the ALD deposited insulating layer. So far, by using a newly developed process, MIM tunneling diode with micron-scale self-aligned cross-fingers have been successfully demonstrated. Some preliminary DC characterizations have been carried out, and device characteristics such as responsivity, I-V, and C-V curves are documented. Ongoing research for modeling of MIM tunneling diode based on measured data and further reduction of the device junction area enabled by the new process will lead to MIM diode that could detect the infrared and terahertz spectra with greatly enhanced responsivity.