Influence of surface processing in a BCl$_3$ plasma on the formation of ohmic contacts to AlGaN/GaN structures

Conditions for the surface processing of a cap GaN layer in AlGaN/GaN high-electron-mobility transistor (HEMT) structures in a BCl$_3$ plasma have been found. They make it possible to considerably reduce the resistance of ohmic contacts to Group III nitride-based field-effect transistors. The primary factor behind this effect is the noticeable lowering of a potential barrier on the GaN surface through the formation of nitrogen vacancies that act as donors and, correspondingly, a rise in the surface concentration of electrons.