Vertical InGaAs Channel Metal–Insulator–Semiconductor Field Effect Transistor with High Current Density

Abstract

A high-speed transistor operation is expected from using an undoped channel region. We propose a vertical InGaAs-channel metal–insulator–semiconductor field effect transistor (MISFET) with an ultra-narrow mesa structure, an undoped channel, and a heterostructure launcher. According to a Monte Carlo simulation, a cutoff frequency of 1.5 THz is expected when a 20-nm-wide mesa structure, a 60-nm-long channel, and a 5 MA/cm2 drain current density are achieved. We fabricated an ultra-narrow mesa structure by using selective undercut etching. In the fabricated device, the channel mesa was 15 nm wide, and the observed drain current density was 0.95 A/mm. Because the channel mesa width was 15 nm, the drain current density per unit area was 6.3 MA/cm2. A high current density was achieved for a short charging time. By comparing the drain current density of the 60-nm-long channel device with that of a 100-nm-long channel device, we inferred that quasi-ballistic transportation can be achieved in our devices.