Patent ID: 7015498

Claim:
A quantum optical semiconductor device, comprising: a semiconductor substrate; and an active layer formed on said semiconductor substrate and including therein a quantum structure, said quantum structure comprising: a first barrier layer of a first semiconductor crystal having a first lattice constant and a first bandgap; a second barrier layer of a second semiconductor crystal formed epitaxially on said first barrier layer, said second semiconductor crystal having a second lattice constant and a second bandgap; a plurality of quantum dots formed in said second barrier layer, each of said quantum dots comprising a semiconductor crystal forming a strained system with regard to said first and second semiconductor crystals and having a lattice constant different from said first lattice constant and a bandgap smaller than any of said first and second bandgaps, each of said quantum dots having a height substantially identical with a thickness of said second barrier layer; and a third barrier layer of a third semiconductor crystal formed on said second barrier layer, said third semiconductor crystal having a lattice constant different from said lattice constant of said semiconductor crystal constituting said quantum dots, said third semiconductor crystal further having a third bandgap larger than said bandgap of said semiconductor crystal forming said quantum dots, said third barrier layer making a contact with an apex of said quantum dot formed in said second barrier layer, wherein each of said quantum dots has an in-plane strain equal to or larger than a strain acting in a direction perpendicular to said substrate for the case where a tensile strain is defined to have a positive value and a compressive strain is defined to have a negative value.