Semiconductor laser

A semiconductor laser, comprising:

• a p-type semiconductor region;
• an n-type semiconductor region;
• and
• an active layer which is provided between the p-type semiconductor region and the n-type semiconductor region, and has a type II quantum well structure,
• wherein the type II quantum well structure includes
• a well layer made of a III-V compound semiconductor and
• a plurality of barrier layers that provide respective barriers for electrons and holes in the well layer,
• wherein, in the type II quantum well structure, the well layer is provided between the barrier layers,
• wherein the well layer includes a first region and a second region, the first region having a low potential for electrons in the well layer and a high potential for holes in the well layer, the second region having a high potential for electrons in the well layer and a low potential for holes in the well layer, the high potential of the second region being higher than the low potential of the first region, the low potential of the second region being lower than the high potential of the first region, and
• wherein the first region and the second region of the well layer are arranged in a direction from one of the barrier layers to another of the barrier layers.