Millimeter-wave GaN-based HEMT development at ETH-Zürich

Abstract

We review the AlGaN/GaN high electron mobility transistor (HEMT) activities in the Millimeter-Wave Electronics Group at ETH-Zürich. Our group's main thrust in the AlGaN/GaN arena is the extension of device bandwidth to higher frequency bands. We demonstrated surprising performances for AlGaN/GaN HEMTs grown on high-resistivity (HR) silicon (111) substrates, and extended cutoff frequencies of 100 nm gate devices well into the millimeter (mm)-wave domain. Our results narrow the performance gap between GaN-on-SiC (or sapphire) and GaN-on-silicon and establish GaN-on-Si as a viable technology for low-cost mm-wave electronics. We here contrast the difference in behaviors observed in our laboratory between nominally identical devices built on high-resistivity silicon (HR-Si) and on sapphire substrates; we show high-speed devices with high-cutoff frequencies and breakdown voltages which combine fT,MAX × BV products as high as 5–10 THz V, and show AlGaN/GaN HEMTs with fT values exceeding 100 GHz on HR-Si. Although the bulk of our activities have so far focused on AlGaN/GaN HEMTs on HR-Si, our process produces excellent device performances when applied to GaN HEMTs on SiC as well: 100 nm gate transistors with fT > 125 GHz have been realized at ETH-Zürich.

Single and double‐gate based AlGaN/GaN MOS‐HEMTs for the design of low‐noise amplifiers: a comparative study

“…These devices have tremendously attracted radio‐frequency (RF) circuit design engineers to design power amplifiers (PAs) [3] and low‐noise amplifiers (LNAs) [4, 5], which can be used for the next generation RF front end transceivers. In order to enable high frequency and low noise operation of the device, the gate length of the device must be scaled down [6]. In fact, one of the possible techniques to reduce the noise figure of the device is to enhance the cut‐off frequency of the device since both are interrelated with each other [7].…”

“…In fact, one of the possible techniques to reduce the noise figure of the device is to enhance the cut‐off frequency of the device since both are interrelated with each other [7]. However, with a decrease in gate length, there is a significant increase in gate leakage current, which in turn produces different short‐channel effects (SCEs), such as drain‐induced barrier lowering (DIBL) and, channel length modulation (CLM) [6]. However, these effects deteriorate device performances.…”