Influence of Mg Out‐Diffusion Effect on the Threshold Voltage of GaN‐Based p‐Channel Heterostructure Field‐Effect Transistors

Abstract

To resolve the parasitic problems and to fully leverage the superiority of GaN‐based high electron mobility transistors, monolithic integration of different function blocks is a promising solution. The enhancement mode (E‐mode) GaN‐based p‐channel heterostructure field‐effect transistor (p‐HFET) is one of the key components. Herein, the threshold voltage (VTH) is modeled, and the influence of the Mg out‐diffusion effect on VTH is investigated. The impact of the diffusion coefficient of Mg, the Mg concentration in the p‐GaN layer, the thicknesses of the AlGaN layer (tb), p‐GaN channel layer (tch), and an oxide layer (tox) on VTH are all taken into consideration for systematic exploration. The analysis illustrates that lower Mg concentration, smaller diffusion coefficient, and thinner p‐GaN channel and AlGaN layers facilitate the realization of E‐mode p‐HFETs. Furthermore, it can be observed that lower Mg concentration in the p‐GaN layer diminishes the VTH sensitivity to the thickness of the p‐GaN channel layer. Hence, a heterostructure with two p‐GaN layers of different concentrations is suggested to reduce the complexity of the etching technique while improving the ohmic contacts. As a result, the model can effectively guide the design of GaN‐based E‐mode p‐HFETs.