An over 100 W AlGaN/GaN enhancement‐mode HEMT power amplifier with piezoelectric‐induced cap structure

A novel piezoelectric‐induced cap structure in an AlGaN/GaN high electron mobility transistor (HEMT) was developed for enhancement‐mode (E‐mode) operation with high maximum drain current density (Idmax), high breakdown voltage (BVgd) and small current collapse. Our developed cap structure consists of a thin GaN/AlN/ GaN triple‐layer, which reduces the sheet resistance (Rsh) due to conduction band bending. The threshold voltage (Vth) is +0.25 V with a high Idmax of 520 mA/mm, a high BVgd of 336 V and small current collapse by using the developed cap structure and a gate recess technique. The single‐chip AlGaN/GaN E‐mode HEMT amplifier achieved a high output power of 126 W at 2.5 GHz with improved distortion characteristics. This is the first report of an AlGaN/GaN E‐mode HEMT with an output power of over 100 W. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)