US Patent 7522645 Nitride-based semiconductor laser device

A nitride-based semiconductor laser device, includes: a first cladding layer of a first conductivity type; an active layer formed above the first cladding layer; an overflow-preventing layer of a second conductivity type formed on the active layer; and a second cladding layer of the second conductivity type formed above the overflow-preventing layer. The active layer includes three barrier layers and two well layers so that each well layer can be inserted between the corresponding ones of the three barrier layers and two of the three barrier layers are located on the outer sides of both well layers, thereby constituting a double-layered quantum well layer. The thickness of each well layer is set within a range of 2 to 5 nm.