Sn-doped n-type GaN layer with high electron density of 1020 cm-3 grown by halide vapor phase epitaxy

A Sn-doped n-type GaN layer with a high electron density of 2 x 1020 cm-3 and a low resistivity of 8.7 x 10-4 omega center dot cm was grown by halide vapor phase epitaxy (HVPE). Sn doping was performed through the reaction between Sn metal and HCl gas. The Sn concentration markedly increased with decreasing growth temperature and the activation energy of Sn desorption from the GaN surface was found to be 4.1 eV. Smooth surfaces were obtained by introducing the Sn precursor even though the samples were grown at a low temperature of 905 degrees C, suggesting that Sn atoms act as surfactants and promote the migration of Ga adatoms. Almost all the Sn atoms act as donors in GaN below the Sn concentration of 2 x 1020 cm-3. These results indicate that using the Sn donor is promising for fabricating low-resistivity n-type GaN substrates by HVPE.