metalorganic vapor phase epitaxy in the following manner this process is referred to as movpe hereinafter the gases employed in this process are nh 3 h 2 as carrier gas trimethyl gallium ga ch 3 3 tmg hereinafter trimethyl aluminum al ch 3 3 tma hereinafter silane sih 4 and diethyl zinc dez hereinafter the sapphire substrate 1 of single crystal with its principal crystal plane a surface 1120 cleaned by solvent washing and heat treatment was set on the susceptor placed in a reaction chamber of an movpe apparatus the sapphire substrate 1 underwent vapor phase etching at 1100 u00b0 c with h 2 flowing through the reaction chamber at a flow rate of 2 l min under normal pressure on the sapphire substrate 1 was formed the aln buffer layer 2 about 500 u00e5 thick at 400 u00b0 c by supplying h 2 at a flow rate of 20 l min nh 3 at a flow rate of 10 l min and tma at a flow rate of 1 8 u00d7 10 u2212 5 mol min on the buffer layer 2 was formed the n layer 3 of high carrier concentration 1 5 u00d7 10 18 cm 3 of 2 2 u03bcm thick gan by supplying h 2 at a flow rate of 20 l min nh 3 at a flow rate of 10 l min tmg at a flow rate of 1 7 u00d7 10 u2212 4 mol min and silane diluted to 0 86 ppm with h 2 at a flow rate of 200 ml.