Oskar Sadowski
supervisor: Mariusz Sochacki
The main goal of my PhD thesis is to develop manufacturing technology of low resistive ohmic contacts for GaN based vertical power devices. The scope of research includes analysis of influence of technological aspects (thicknesses of metallic layers, substrate surface preparation methods, annealing temperatures and atmosphere) on ohmic contact properties and an attempt to explain the mechanism of formation of ohmic contacts to n-type GaN (including n-type GaN substrate with nitrogen-face surface (N-face)) and p-type GaN.
In first year of my doctoral studies, I was working on ohmic contacts to p-type epitaxial GaN layer and to N-face n type GaN substrate. In order to optimize the ohmic contact to p-type GaN the samples with metal contacts containing Ni, Au and Pd were prepared and characterized. The Ti /Al-based ohmic contacts were prepared and characterized for N-face n-type GaN substrates as well as on Ga-face n-type epitaxial GaN layers for comparison. The resistivity (ρc) of ohmic contacts was estimated by circular transfer lenght method (cTLM). As a result Ni/Au ohmic contacts with ρc =2x10-4 Ωcm2 for p-type GaN and ~1x10-6 Ωcm2 for N-face n-type GaN substrate were obtained.
This work was partially supported by The National Centre for Research and Development under Agreement nr TECHMATSTRATEG-III/0003/2019 for project „Complete vertically integrated technological chain for vertical GaN-on-GaN power electronics: from GaN substrate to Intelligent Energy Bank”.