Demonstration of GaN Current Aperture Vertical Electron Transistors With Aperture Region Formed by Ion Implantation
In this paper, we report the successful demonstration of current aperture vertical electron transistors (CAVETs) obtained by using a novel implantation-based compensation method to achieve a conductive aperture. This innovation leads to the first demonstration of “regrowth-free” CAVETs. Two gallium nitride (GaN) CAVETs were fabricated using the ion-implantation-compensated aperture regions, both with Mg-doped p-GaN as current-blocking layers (CBLs). The aperture regions were formed by implanting Si into the p-GaN CBL. In one of the CAVET samples, the Si-implantation-based aperture was formed prior to the regrowth of AlGaN/GaN layers on top. The other CAVET sample was subjected to aperture formation via Si implantation after all the device layers were grown. An ion-implantation scheme using multiple-energy levels was designed to realize a 250-nm Si box profile with a total dose of <inline-formula> <tex-math notation="LaTeX">$\textsf {4.2} \times \textsf {10}^{\textsf {15}}$ </tex-math></inline-formula> cm<sup>−2</sup>, converting a 250-nm p-GaN (Mg: <inline-formula> <tex-math notation="LaTeX">$8\times 10^{\textsf {19}}$ </tex-math></inline-formula> cm<sup>−2</sup>) to conductive (n-type) GaN successfully. This novel fabrication method enables the use of Mg-doped CBLs without conventional etch and regrowth steps. Moreover, the proposed scheme can ultimately lead to regrowth-free CAVETs.