Influence of fluorine implantation on the physical and electrical characteristics of GaN-on-GaN vertical Schottky diode

Abstract

Fluorine implantation has been reported to be effective in suppressing electric fields at the edge of Schottky contacts in GaN due to the formation of fixed negative charged traps. In this study we show a detailed investigation into the behavior of fluorine implantation in GaN on material and electrical properties, and reproduce these electrical properties using TCAD simulations. A reduction in the free carrier concentration is observed by both μ-Raman, SSRM and C−V measurements, likely due to the trapping of free electrons by fluorine ions. The barrier height extracted from C-V measurements increases with increasing implant overlap area under the Schottky contact, whereas the barrier height extracted from I-V measurements remains constant. For the device without any implantation, the extracted barrier height remained the same for both extraction methods. This observation suggests the existence of a high and low double barriers originating from the implant and non-implant region respectively. TCAD simulations performed by including negative charge support the formation of a double barrier. By using the barrier height extracted from C-V measurements for the implanted region, we were able to use our TCAD model to estimate the profile of fixed negative charge, which is around 10% of the total implanted fluorine. This understanding shows that for effective design of edge terminations using fluorine implantation, consideration of the fixed negative charge as a percentage of the fluorine implantation is very important.