Theoretical Study of Double-Heterojunction AlGaN/GaN/InGaN/δ-doped HEMTs for Improved Transconductance Linearity

The aim of this study is to propose a novel double-heterojunction high electron mobility transistor (DH-HEMT) structure, Al 0.3 Ga 0.7N/GaN/In 0.15 Ga 0.85N/ d-doped, to improve transconductance linearity. A theoretically based quasi-two-dimensional model is well calibrated with experiments and is used to project the transistor performance. It is found that a thin In 0.15 Ga 0.85N back barrier and d-doped layer significantly enhance carrier confinement and increase carrier concentration in the channel. It is the combination effect of enhanced carrier confinement and increased carrier concentration that leads to a larger voltage swing. A wider linear range of transconductance can be achieved on account of the larger voltage swing. Moreover, this novel structure not only improves the transconductance linearity but also increases its maximum transconductance and the corresponding drain current, which is beneficial to high power and high frequency applications.