While depositing a III-V compound semiconductor layer from a vapor, carbon is added to group III and V elements to produce a p type conductivity region in the depositing semiconductor layer. Then, a small amount of n type dopant is added to the group III and V elements together with the carbon to produce an n type conductivity region in the depositing semiconductor layer. A sharp and precisely controlled doping profile is produced in the vicinity of a p-n junction, resulting in a semiconductor device having good initial performance and high reliability.