Gain spectroscopy and vertical cavity devices in wide-gap semiconductors

The InGaN quantum-well diode laser is now reaching the threshold of commerc ial availability as an edge emitting blue/violet device, yet many questions remain concerning the details of its operation. For example, the threshold current density in the best cw InGaN QW lasers is still about one order of magnitude larger than that in the green ZnCdSe QW diode devices, in spite of the materials being quite similar in the effective mass band picture. On the one hand, the nitride semiconductors are remarkably tolerant of built- in crystalline defects at high current densities. On the other, the microsc opics of optical gain are significantly influenced by crystalline 'disorder ' that emanates from indium compositional anomalies in the active InGaN qua ntum-well material. (C) 2000 Elsevier Science B.V. All rights reserved.