Si- and Sn-Doped Homoepitaxial β-Ga2O3 Layers Grown by MOVPE on (010)-Oriented Substrates

We studied the growth of Si-and Sn-doped homoepitaxial beta-Ga2O3 layers on (010)-oriented substrates by metal organic vapor phase epitaxy (MOVPE). At optimal growth conditions (850 degrees C, 5 mbar) the layers were smooth with RMS roughness values of similar to 600 pm. A microstructural study by transmission electron microscopy (TEM) revealed a very high crystalline perfection of the layers. No dislocations or planar defects were observed within the field of view of TEM. Using Si as dopant, the free electron concentration could be varied in a range between 1 x 10(17) and 8 x 10(19) cm(-3), while with Sn the doping range was restricted to 4 x 10(17)-1 x 10(19) cm-3. This was explained by a pronounced Sn memory effect in the MOVPE reactor that hampers achieving low carrier densities and by incorporation issues that limit the doping efficiency at high Sn doping levels. The electron mobility for a given doping density increased from similar to 50 cm(2)/Vs for n = 8 x 10(19) cm(-3) to similar to 130 cm(2)/Vs for n = 1 x 10(17) cm(-3) independently of the dopant. These values match the best literature data relative to beta-Ga2O3 bulk crystals and layers grown by molecular beam epitaxy, setting a new standard for MOVPE-grown layers. (C) The Author(s) 2016. Published by ECS.