We investigate possible routes how to realize vertical field effect transistors based on GaN (following the CAVET design, see below). One challenge here is the realization of a so-called current aperture, i.e. a layer in the device which enables only well-defined local vertical current flow. Such a current blocking layer may be fabricated by a Mg-doped GaN layer. The insulation character can be determined by I-V measurements on mesa structures.
To realize a current aperture, the layer needs to be locally open which can be done bylithography and local dry etching, alternatively by selective area epitaxy.
Eventually, we intend to fabricate and characterize complete VFET devices with our cooperation partner, the Fraunhofer Institute of Solid State Physics (Freiburg).
Current-Aperture Vertical Electron Transistor (CAVET)
(from S. Chowdhury et al., Semicond. Sci. Technol. 28 (2013) 074014).