Dependence of threshold voltage on doped layer thickness in AlGaN/GaN HEMT: An improved split donor E-mode design

We present a novel and simple technique to control the threshold voltage of AlGaN/GaN High Electron Mobility Transistors. We use an in-house built self-consistent Schrödinger-Poisson simulator to model the dependence of threshold voltage of HEMT on its doped layer thickness. The simulator has been designed for finding the optimum threshold voltage for required mode of operation by changing doped layer thickness. It is shown that we can achieve enhancement mode of operation by reducing the doped layer thickness. However, this technique has a tradeoff that it reduces current too. Finally, an improved split donor enhancement mode HEMT design is proposed that effectively reduces doped layer thickness without minimizing current. The proposition would be helpful in designing enhancement mode devices at low cost.