Electron mobility in GaN layers and HEMT structure optimized by MOVPE technological parameters

•Influence of growth parameters on transport properties of GaN was systematically studied.•Optimal technology to achieve high electron mobilities was identified.•Optimal growth conditions were 950 °C, TEGa, low growth rate, nitrogen atmosphere, 150 mbar.•Improved channel technology increased electron mobility in the channel by 30 % to 1896 cm2/vs.•Necessity to check reliability of van der Pauw results by CV measurement is demonstrated. Although a lot of attention was devoted to different aspects of GaN high electron mobility transistor (HEMT) structure such as buffer layer architecture, AlGaN barrier, surface passivation and dielectric choice, not much attention was paid to optimize the technology of GaN channel. We show in this work that by optimizing the channel technology the electron mobility can be significantly improved. We have studied the influence of technological parameters on transport properties on the series of GaN layers resembling a HEMT channel. We pay most attention to the layer growth using TEG precursor. The examined parameters were type of reactor atmosphere, growth temperature, growth rate influenced by precursor concentration and reactor pressure. Using optimized parameters for growth of a HEMT structure, we have succeeded in increasing the electron mobility in 2DEG by 30 %.