Compound semiconductor device and method of manufacturing the same

A method of manufacturing a compound semiconductor device, comprising:

• forming a p-type first semiconductor layer containing antimony over a substrate;
• forming a fourth semiconductor layer containing phosphorus over the first semiconductor layer;
• forming a p-type second semiconductor layer containing antimony over the fourth semiconductor layer;
• forming an n-type third semiconductor layer over the second semiconductor layer;
• etching the third semiconductor layer and the second semiconductor layer until the fourth semiconductor layer is exposed;
• etching the fourth semiconductor layer until the first semiconductor layer is exposed;
• forming a first electrode in ohmic contact with the first semiconductor layer;
• and
• forming a second electrode in ohmic contact with the third semiconductor layer,
• wherein the first semiconductor layer is made from a material whose contact resistance with the first electrode is lower than that of the second semiconductor layer, and
• the fourth semiconductor layer has a thickness in which electrons tunnel between the first semiconductor layer and the second semiconductor layer.