Ion Implantation Doping in Silicon Carbide and Gallium Nitride Electronic Devices

Wide band gap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) are excellent materials for the next generation of high-power and high-frequency electronic devices. In fact, their wide band gap (>3 eV) and high critical electric field (>2 MV/cm) enable superior performances to be obtained with respect to the traditional silicon devices. Hence, today, a variety of diodes and transistors based on SiC and GaN are already available in the market. For the fabrication of these electronic devices, selective doping is required to create either n-type or p-type regions with different functionalities and at different doping levels (typically in the range 1016–1020 cm−3). In this context, due to the low diffusion coefficient of the typical dopant species in SiC, and to the relatively low decomposition temperature of GaN (about 900 °C), ion implantation is the only practical way to achieve selective doping in these materials. In this paper, the main issues related to ion implantation doping technology for SiC and GaN electronic devices are briefly reviewed. In particular, some specific literature case studies are illustrated to describe the impact of the ion implantation doping conditions (annealing temperature, electrical activation and doping profiles, surface morphology, creation of interface states, etc.) on the electrical parameters of power devices. Similarities and differences in the application of ion implantation doping technology in the two materials are highlighted in this paper.

Selective Doping in Silicon Carbide Power Devices

Silicon carbide (SiC) is the most mature wide band-gap semiconductor and is currently employed for the fabrication of high-efficiency power electronic devices, such as diodes and transistors. In this context, selective doping is one of the key processes needed for the fabrication of these devices. This paper concisely reviews the main selective doping techniques for SiC power devices technology. In particular, due to the low diffusivity of the main impurities in SiC, ion implantation is the method of choice to achieve selective doping of the material. Hence, most of this work is dedicated to illustrating the main features of n-type and p-type ion-implantation doping of SiC and discussing the related issues. As an example, one of the main features of implantation doping is the need for post-implantation annealing processes at high temperatures (above 1500 °C) for electrical activation, thus having a notable morphological and structural impact on the material and, hence, on some device parameters. In this respect, some specific examples elucidating the relevant implications on devices’ performances are reported in the paper. Finally, a short overview of recently developed non-conventional doping and annealing techniques is also provided, although these techniques are still far from being applied in large-scale devices’ manufacturing.