Semiconductor laser

A semiconductor laser comprising:

• a semiconductor substrate of a first conductivity type;
• a clad layer of said first conductivity type formed on said substrate;
• a guide layer of said first conductivity type formed on said clad layer;
• an active layer formed on said guide layer, said active layer having a first barrier layer doped with an impurity of a second conductivity type opposite to said first conductivity type, a first undoped spacer layer with thickness of 2 to 4 nm formed on said first barrier layer, an undoped well layer formed on said first spacer layer, an undoped second spacer layer formed on said well layer, and a second barrier layer doped with said second conductivity impurity formed on said second spacer layer;
• a second conductivity type guide layer formed on said active layer;
• a second conductivity type clad layer formed on said second conductivity type guide layer;
• a contact layer formed on said second conductivity type clad layer;
• a first electrode formed on a top surface of said contact layer;
• a second electrode formed on a rear surface of said substrate;
• and
• a pair of opposed end surfaces extending between said top surface and said rear surface to provide a resonant cavity for laser light.

A semiconductor laser diode comprising:

• a semiconductor substrate of a first conductivity type;
• a first clad layer of said first conductivity type formed on said substrate;
• a first guide layer of said first conductivity type formed on said clad layer;
• an active layer formed on said guide layer, said active layer having a first undoped barrier layer, a first doped barrier layer formed on said first undoped barrier layer with an impurity of a second conductivity type opposite to said first conductivity type, a first undoped spacer layer with thickness of 2 to 4 nm formed on said first barrier layer, an undoped well layer formed on said first spacer layer, an undoped second spacer layer formed on said well layer, a second doped barrier layer doped with second conductivity impurity formed on said second spacer layer and a second undoped barrier layer formed on said second doped barrier layer;
• a second clad layer of a second conductivity type layer formed on said second guide layer;
• a contact layer formed on said second clad layer;
• a first electrode formed on a top surface of said contact layer;
• a second electrode formed on a rear surface of said substrate;
• and
• a pair of opposed end surfaces extending between said top surface and said rear surface to provide a resonant cavity for laser light.