Ammono, the manufacturer of high quality bulk GaN, announces achievement of two types of semi-insulating material: 1) optimised substrates, in which oxygen donors are compensated by shallow Mg acceptors (type-I), 2) the ammonothermal GaN substrates doped with deep acceptors in form of transition metal ions (type-II), shown for the first time. In these substrates the oxygen concentration was about 1x1018 cm-3. The substrates were studied by measuring their resistivity by contactless techniques, such as microwave resonance and various capacitance methods. Both types of material show dielectric properties, with improved resistivity of at least 1011 Ωcm, being stable after annealing at 1100 °C, indicating they can be used at epitaxial growth conditions without change of electric properties. Extrapolation of high temperature dependence of resistivity yielded room temperature resistivity (type-II substrate) of 8x1012 Ωcm.
Detailed characterization of the substrates was presented during the European Material Research Society Fall Meeting held in Warsaw, 15-20th of September 2015.
We are convinced, that described substrates can be used in fabrication of High Electron Mobility Transistors for radiolocation purposes and many others.