Metal-Insulator-Metal Diodes for High Frequency Applications

Abstract

Ultrafast electrical components have been required to apply to various devices such as the high-speed computer, the optoelectronic devices, and the communication systems. Recently for the communication field, the demanded frequency almost approaches THz range. Thus, electrical components, operated in terahertz (THz) area, should be developed. One of the challenging electrical devices is a diode, which has rectifying characteristics. Schottky diode has been used widely to convert alternative current (AC) to direct current(DC) in high frequency area. Unfortunately, the applied frequency of Schottky diodes is limited below THz level. Metal-insulator-metal (MIM) diode has been studied to overcome the frequency limit due to its fast response time. Some MIM diode results have expected theoretically an operation up to 100THz level by the nano-scale small junction dimension and the tunneling current. Therefore, from this structure we can have a motivation to solve the limit for various THz applications. Our purpose is to improve the asymmetric of I-V curve as well as the decrease of RC (resistance capacitance) constant time in MIM diode structure for high frequency rectifying performance. To achieve these purposes, a simple vertical MIM diode, a lateral MIM diode, and a metal-insulator-carbon nanotube (MIC) diode have been studied. These devices were fabricated using optical and electron beam lithography, physical vapor deposition(PVD), growth of a vertically aligned carbon nanotube by plasma enhanced chemical vapor deposition (PECVD), and lift-off process. The electric characteristics and figure of merits of these MIM diodes are investigated especially for high-speed operation. The lateral MIM and the MIC structure have shown the nonlinearity and the asymmetric characteristics depending on structural effect and work function difference. Especially in MIC diode, it shows a good rectifying performance up to 10 MHz in direct measurement mode and the estimated maximum cut-off frequency is 3.47 THz. ⓒ 2013 DGIST