AlGaN/GaN high electron mobility transistor structure design and effects on electrical properties

We report on the effect of strain induced polarization fields in AlGaN/GaN heterostructures due to the incorporation of Si dopant ions in the lattice. By Si-doping (Al)GaN, a contraction of the wurtzite unit cell can occur le ading to strain in doped AlGaN/GaN heterostructures such as high electron m obility transistors (HEMTs). In a typical modulation doped AlGaN/GaN HEMT s tructure, the Si-doped AlGaN supply layer is separated from the two-dimensi onal electron gas channel by an undoped AlGaN spacer layer. This dopant-ind uced strain, which is tensile, can create an additional source of charge at the AlGaN:Si/AlGaN interface. The magnitude of this strain increases as th e Si doping concentration increases and the AlN mole fraction in the AlGaN decreases. Consideration of this strain should be given in AlGaN/GaN HEMT s tructure design.