Electrophysical parameter comparison of 2DEG in AlGaN/GaN heterostructures grown by the NH3-MBE technique on sapphire and silicon substrates

•AlN/GaN layers alternation allows to grow crack-free GaN layers by NH3-MBE.•GaN layers grown under the same growth conditions on Al2O3 and Si substrates have the same surface morphology.•Dislocation density in GaN layers grown on Si substrate up to 5 times higher than in GaN layers on Al2O3 substrate.•2DEG electron mobility in AlGaN/GaN heterostructures on Si substrate 30% lower than in HES on Al2O3 substrate.