Submicrometer‐Thick Step‐Graded AlGaN Buffer on Silicon with a High‐Buffer Breakdown Field

Abstract

Submicrometer‐thick AlGaN/GaN high‐electron‐mobility transistor (HEMT) epilayers grown on silicon substrate with a state‐of‐the art vertical buffer breakdown field as high as 6 MV cm−1 enabling a high transistor breakdown voltage of 250 V for short gate‐to‐drain distances despite such a thin structure are reported. HEMTs with a gate length of 100 nm exhibit good DC characteristics with a low drain‐induced barrier, going as low as 100 mV V−1 for a VDS of 30 V. Breakdown voltages of each epilayer from the decomposed heterostructure reveals that the outstanding breakdown strength is attributed to the insertion of Al‐rich AlGaN in the buffer layers combined with an optimized AlN nucleation layer. As a result, large signal measurements at 10 GHz could be reliably achieved up to VDS = 35 V despite the use of a 100 nm gate length. These results demonstrate the potential of submicrometer‐thick buffer GaN‐on‐Si heterostructures for high‐frequency applications.