High-resistance GaN-based buffer layers grown by a polarization doping method.

A high-resistance buffer layer is critical for GaN-based high electron mobility transistors (HEMTs) to suppress the drain leakage current and pre-mature device breakdown. A typical method to obtain the HR buffer layers is the acceptor impurity doping that is able to provide holes to compensate the background electrons in the buffer layers. However, the intentional doped acceptor impurities such as Mg, Fe and C will result in current collapse in GaN-based HEMTs. To address this issue, in this work, we employed a polarization doping method of holes by Al-composition grading instead of the acceptor impurity doping. The sheet resistance of the GaN-based buffer layer significantly increased due to the holes generated by the polarization field. (a) Structures of the three samples; (b) Schematic illustration of polarization-induced 3DHG in (0001)-oriented graded AlGaN layer; (c) The square resistance of the three samples calculated by using CTLM. [ABSTRACT FROM AUTHOR]