Abstract: This invention relates to a method of growing a nitride semiconductor layer by molecular beam epitaxy comprising the steps of: a) heating a GaN substrate (S) disposed in a growth chamber (10) to a substrate temperature of at least 850° C.; and b) growing a nitride semiconductor layer on the GaN substrate by molecular beam epitaxy at a substrate temperature of at least 850° C., ammonia gas being supplied to the growth chamber (10) during the growth of the nitride semiconductor layer; wherein the method comprises the further step of commencing the supply ammonia gas to the growth chamber during step (a), before the substrate temperature has reached 800° C.

Abstract: A method of growing a Group III or Group III-V nitride layer on a semiconductor substrate includes the steps of: locating, within a chamber, the semiconductor substrate having on its surface a Group III-V semiconductor layer incorporating a substance which is strongly reactive with nitrogen; and subsequently effecting nitridation of the Group III-V semiconductor layer by introducing a species containing nitrogen into the chamber to cause a reaction between the nitrogen and the substance.

Abstract: A separate confinement heterostructure (SCH) laser device (LD) has: a quantum well active region within an optical guiding region; and, n-type and p-type cladding regions provided on opposite sides of the optical guiding region. An electron-capture layer is provided in the n-side portion of the optical guiding region. The composition of the electron-capture layer is set in such a manner that the minimum energy for X-electrons in the conduction band is lower than that in the surrounding parts of the active region and/or the n-side portion of the optical guiding region. The electron-capture layer is thick enough to bind X-electrons so that, in use, the electron-capture layer promotes the capture of the X-electrons. The electron-capture layer is disposed sufficiently close to the active region to permit transfer ot the captured X-electrons to at least one .GAMMA.-confined level in the active region.