Optimisation of trench filling in GaN towards vertical HEMT structures

Abstract

In this work we present studies how to fill epitaxially trenches in a GaN layer in order to form a current aperture for use in 3D high power field effect transistors. By optimising various growth parameters in our metal organic vapour phase epitaxy, we achieved an almost complete and smooth filling of 5 μm wide and 500 nm deep trenches etched into a GaN:Mg layer by reactive-ion etching. By using GaN:Si marker layers, the filling process could be excellently monitored. Eventually, a high electron mobility transistor structure was deposited on top of the optimized structures enabling an electrical assessment of this process.