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

Abstract

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)

Current status of GaN power devices

“…These are summarized in Table I. The first proposed structure uses a recessed-gate approach [8], in which the AlGaN barrier layer (∼20 nm thick) below the gate is etched to a thickness of 2∼5 nm, which causes the 2DEG to almost vanish in this region, causing a positive shift in the threshold voltage. However, it is difficult to completely deplete the 2DEG in order to obtain a sufficiently high threshold voltage.…”

Drift region optimization in high‐voltage GaN MOS‐gated HEMTs

“…The GaN cap has been used to achieve better surface smoothness in GaN HEMT epi layers [10], and reduce current collapse [11]. GaN MOS-HEMT that has a GaN cap layer with high breakdown voltage has also been reported [12].…”

GaN for automotive applications

“…In recess structure [4], the barrier layer of AlGaN at channel region is etched to make thinner AlGaN under the gate. The 2DEG density is proportional to the AlGaN layer thickness.…”