Abstract: A quantum-well semiconductor laser/amplifier mounted on a highly conductive semiconductor substrate. Inactive regions include a highly doped N-region and a highly doped P-region. The N-region is composed of semiconductor material mounted on the substrate. The active region includes a quantum-well heterostructure of intrinsic semiconductor material that mounts on the N-region. The quantum-well structure includes a series of quantum wells, each having barrier layers, quantum-well layers, and a delta-strained layer mounted near the center of the quantum wells. The delta-strained layers are very thin, being formed from a number of mono-layers of semiconductor material. There is a large lattice mismatch between each of the delta-strained layers and its adjacent quantum-well layers. The band edges of the quantum-well layers and the delta-strained layers are located at substantially the same level. The P-region is composed of a semiconductor material that mounts on the quantum-well structure.