The influence of an underlying 2-dimensional electron
gas (2DEG)
on the performance of a normally off p-type metal oxide semiconductor
field effect transistor (MOSFET) based on GaN/AlGaN/GaN double heterojunction
is analyzed via simulations. By reducing the concentration of the
2DEG, a greater potential can be dropped across the GaN channel, resulting
in enhanced electrostatic control. Therefore, to minimize the deleterious
impact on the on-state performance, a composite graded back-to-back
AlGaN barrier that enables a trade-off between n-channel devices and
Enhancement-mode (E-mode) p-channel is investigated. In simulations,
a scaled p-channel GaN device withLG=
200 nm,LSD= 600 nm achieves anIONof 65 mA/mm, an increase of 44.4% compared
to a device with an AlGaN barrier with fixed Al mole fraction,ION/IOFFof ∼1012, and |Vth| of | – 1.3
V|. For the n-channel device, the back-to-back barrier overcomes the
reduction ofIONinduced by the p-GaN
gate resulting in anIONof 860 mA/mm,
an increase of 19.7% compared with the counterpart with the conventional
barrier with 0.5 V positiveVthshift.