Patent ID: 7183584

Claim:
A quantum well structure in which a stack of alternating layers including a quantum well layer and a barrier layer comprising a III-group nitride semiconductor are laminated in a direction of a crystal axis expressed in [x, y, −(x+y), z] (where x and y are any integer numbers and z is a natural number), wherein the barrier layer includes an n-type region doped with n-type impurity and an undoped region, an impurity concentration of the n-type region is 5E18 cm −3 or less on an average, thickness of the undoped region is 5 nm or more, an upper surface of the barrier layer consists of the undoped region and a lower surface of the barrier layer consists of the n-type region, and an upper surface of the quantum well layer is situated next to one of the n-type regions and a lower surface of the quantum well layer is situated next to one of the undoped regions.