Method for manufacturing a luminescent diode having a high frequency and high limit frequency for its modulation capability

#The present invention relates to a luminescent diode formed from a mixed crystal epitaxial layer comprising a composition A.sub.1-x.sup.III Al.sub.x B.sup.V with a substantially continuously varying value x. A pn-junction is present in the layer formed between n and p-doped layer components.

#For more than half a decade there have been luminescent diodes consisting of gallium-aluminum-arsenide in whose mixed crystal-epitaxial layer the layer-wise local concentration of the aluminum fraction, which replaces a corresponding gallium fraction, is variable with a constant gradient. Such a construction of the mixed crystal layer is designated in the art as a "graded-bandgap". Such an arrangement has a bandgap which is constantly greatly varying, corresponding to the constantly changing aluminum concentration, and has the greatest bandgap with the maximum aluminum concentration. The purpose of such a mixed crystal is to be able to allow recombination-luminescence radiation produced in a layered region with at least a virtually constant aluminum concentration to emerge from the entire mixed crystal-layer in such fashion that this radiation penetrates regions of the layer in which (on account of greater aluminum concentration there) the bandgap is greater. Thus, reabsorption of the produced luminescence radiation is prevented to this extent.

#The pn-junction contained in the mixed crystal-layer of a luminescent diode with a "graded-bandgap", whose surface extends perpendicularly to the vector of the gradient of the aluminum concentration, is, in the case of these already long-known luminescent diodes, produced by means of silicon doping. The silicon has an amphoteric doping behavior in such a mixed crystal, specifically if it is dependent upon the deposition temperature.

#FIG. 1 illustrates a diode designed according to the invention;

#FIG. 2 illustrates a diagram of the distribution for aluminum; and

#FIG. 3 illustrates a diagram of the efficiency.

#FIG. 1 designates a mixed crystal layer manufactured by means of epitaxy, and consisting of, for example, gallium-aluminum-arsenide, whose thickness d is provided in an exaggerated manner. Actual layer thicknesses of completed luminescent diodes according to the invention lie in the size range of 150 to 200 .mu.m. The epitaxial deposition of the mixed crystal layer 1 proceeds on a substrate member, illustrated in broken lines, consisting of, for example, gallium arsenide. Already in the manufacturing process of a luminescent diode according to the invention, this substrate member 2 is again removed, since it absorbs the emitted radiation.

#FIG. 2 illustrates the thickness d of the mixed crystal layer 1 plotted on the ordinate versus the x-concentration of aluminum in the respective layer plane .DELTA. d.

#Reference numeral 3 illustrates the most important layer plane of the pn-junction disposed between the n-conductive layer portion 4 and the p-conductive layer portion 5 of the entire mixed crystal layer. Numerals 6 and 7 designate current electrodes for the mixed crystal layer 1. At least electrode 6 is designed in the form of a point, ring, or strip contact through which the radiation emerges.