Radiation-emitting semiconductor device and method of manufacturing same

Abstract

Radiation-emitting semiconductor diodes in the form of diode lasers or LEDs are used inter alia in information processing systems. There is a particular demand for diodes having a low wavelength. A diode laser which emits at 633 nm is a particularly attractive alternative to a helium-neon gas laser. A radiation-emitting semiconductor diode comprising a semiconductor body with a semiconductor substrate of a first conductivity type on which are present at least a buffer layer of the first conductivity type, a first cladding layer of the first conductivity type and made of InAlGaP, an active layer of InGaP or InAlGaP, and a second cladding layer of the second conductivity type and also made of InAlGaP does not fully meet these demands: either the wavelength is comparatively high owing to the occurrence of an ordered structure, or the morphology and crystal quality of the layers is poor. According to the invention, the buffer layer of such a radiation-emitting semiconductor diode comprises aluminum-gallium arsenide, the aluminum content having at least a minimum value belonging to the band gap of the active layer. The minimum Al content is approximately 6 at % for an InGaP band gap of 1,88 eV, and approximately 9 at % for 1,92 eV. As a result, an active layer comprising InGaP emits, for example, at 650 nm while the semiconductor layers still possess a good crystal quality and morphology. When the active layer of a diode laser has a multiple quantum well structure with comparatively thick (approximately 5 nm) well layers, it even emits at 633 nm. In a method according to the invention, a comparatively high growing temperature--preferably approximately 760.degree. C.--and a buffer layer comprising AlGaAs with a suitable aluminum content are used. Ordering of the structure in semiconductor layers comprising InGaP and InAlGaP is counteracted by this.