Abstract
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 with L(G) = 200 nm, L(SD) = 600 nm achieves an I(ON) of 65 mA/mm, an increase of 44.4% compared to a device with an AlGaN barrier with fixed Al mole fraction, I(ON)/I(OFF) of ∼10(12), and |V(th)| of | - 1.3 V|. For the n-channel device, the back-to-back barrier overcomes the reduction of I(ON) induced by the p-GaN gate resulting in an I(ON) of 860 mA/mm, an increase of 19.7% compared with the counterpart with the conventional barrier with 0.5 V positive V(th) shift.