Compound semiconductor light-emitting device including p-type undoped boron-phosphide-based semiconductor layer joined to thin-film layer composed of an undoped hexagonal group III nitride semiconductor

A pn-junction compound semiconductor light-emitting device comprising:

• a crystal substrate;
• a light-emitting part comprising an n-type lower cladding layer, an n-type light emitting layer, and a doped p-type Group III nitride semiconductor upper cladding layer, sequentially formed on the crystal substrate;
• an undoped Group III nitride thin film semiconductor layer, to which no p-type or n-type impurity element has been added thereto, formed on the p-type upper cladding layer;
• and
• an undoped p-type boron-phosphide based semiconductor layer having a sphalerite crystal type, sequentially formed on the undoped Group III nitride thin film semiconductor layer,
• wherein the undoped Group III nitride thin film semiconductor layer is formed of a hexagonal Group III nitride semiconductor,
• the undoped p-type boron-phosphide based semiconductor layer having a sphalerite crystal type is formed on a surface of the undoped Group III nitride thin film semiconductor layer, and
• wherein the undoped Group III nitride thin film semiconductor layer has a surface of a (0001) crystal plane, and the undoped p-type boron-phosphide based semiconductor layer formed on the surface of the (0001) crystal plane is a (111) crystal layer having a [110] direction aligned with an a-axis of the (0001) crystal plane.