Novel double-level-T-gate technology

We developed a novel double-level-T-gate technology based on wet etching of a metal gate interlayer. With the help of this technological process we prepared T-gate feet with widths as small as 200 nm. The major advantage of our process is its use of only standard optical lithography. It allows the fabrication of 100 nanometer size T-gates for transistors. High electron mobility transistors (HEMTs) were fabricated on an AlGaN/GaN/sapphire material structure with an original gate length Lg of 2 μm. Their cutoff frequency of 6 GHz was improved to 60 GHz by etching the gate to a 200 nm length double T-gate contact.