Solar cell and process for producing the same

A method of manufacturing a solar cell, comprising:

• forming a buffer layer comprising a group-III nitride semiconductor on a substrate using a sputtering method;
• forming first and second group-III nitride semiconductor layers including a p-type layer and an n-type layer having a p-n junction therein and an electrode on the buffer layer, the forming of at least one of the first and second group-III nitride semiconductor layers is performed by a sputtering method comprising:
• a first step of alternately repeating a process of supplying only a dopant element and a process of simultaneously supplying a compound comprising a group-III element and a nitrogen raw material, and
• a second step of performing a heat treatment in a range of about 300° C. to about 1200° C. on at least one of the first and second group-III nitride semiconductor layers formed by the first step;
• and
• forming another electrode on the group-III nitride semiconductor layer including a p-type layer and an n-type layer having a p-n junction therein;
• wherein the sputtering method comprises reacting nitrogen in a plasma, radical, or atomic state with a group-III element, thereby forming the layer.