Piezoelectric charge densities in AlGaN/GaN HFETs

Abstract

New estimates of the piezoelectric charge density at (0001) AlGaN/GaN interfaces are provided. Undoped HFET structures grown by both MBE and MOCVD, on sapphire and SiC substrates, exhibit electron densities of ~5 × 1013 cm–2·xAl (where xAl is the aluminium mol fraction in the AlGaN), which can be attributed to piezoelectric effects. These have a significant influence on the design and behaviour of III-V nitride HFETs.