Semiconductor laser with mesa stripe waveguide structure

In a semiconductor laser for emitting a continuous laser light of visible wavelength range, comprising:

• a semiconductor substrate of a first conductivity type made of III-V compound semiconductor material;
• a first semiconductor cladding layer of the first conductivity type provided above said substrate;
• an active layer of semiconductor material formed on said cladding layer;
• a plurality of semiconductor cladding layers of a second conductivity type formed on said active layer, thereby forming a double hetero-structure;
• a first semiconductive contact layer of the second conductivity type which is mesa-shaped ans has slanted sides, said first contact layer comprising a gallium-arsenide based semiconductor material;
• and
• conductive layer means for serving as terminal electrodes of said laser, the improvement wherein said cladding layers include,
• a second semiconductor cladding layer formed on said active layer, and
• a third semiconductor cladding layer formed on said second cladding layer, being mesa-shaped, and having slanted sides defining a waveguide channel, said first to third cladding layers being made of a compound semiconductor material comprising a specific III-V compound semiconductor material containing indium, aluminum and phosphorus, and the improvement further comprising:
• a second semiconductive contact layer provided between said third cladding layer and said first contact layer for serving as an intermediate contact layer having a band gap width which is smaller than that of said third cladding layer and yet greater than that of said first contact layer to thereby reduce the rate of band gap variation between said third cladding layer and said first contact layer so that an electrical resistance therebetween is lowered, said second contact layer comprising III-V compound semiconductor material containing at least indium, gallium and phosphorus;
• and
• a semiconductive, current-blocking layer covering the slanted sides of said third cladding layer and also the slanted sides of said first contact layer, said current-blocking layer being made of III-V compound semiconductor material which contains at least one of gallium and lauminum as its III semiconductor element, and arsenide as its V semiconductor element.