Abstract A semiconductor diode for an injection laser characterized by a pn junction which has a lower threshold value for the diode current and/or which diode is capable of continuous operation at room temperature or above. The radiation producing range or zone of the pn junction has a variation in the concentration of doping with the variation being spatial and periodic. Variations have a maximum concentration of doping in a range of about 1016 through 1020 parts per cubic centimeter, a ratio of maximum concentration to minimum concentration of at least 2:1, and a distance between maximum concentrations, in the order of between 10 and 500 atomic distances in the lattice of the crystal. The variations in the concentration of the doping provides one or more interference bands in the forbidden band located between the conduction band and the valence band. An interference band is adjacent the edge of either the valence or the conduction band and the doping substance is selected in such a way that the transition probability for transit between the conduction band or valence band and the adjacent interference band is essentially larger than for inter-band recombination. To produce the semiconductor material for the diode, the doping material concentration is varied during the growth of the crystal. For example, if the crystal is grown from a gas phase by an epitaxial deposition, the concentration of doping material in the gas phase is varied with respect to the desired periodicity and with respect to the speed and time for the growth of the crystal. If the crystal is formed by epitaxial deposition of the material from the liquid phase, the variation in doping is caused by variations in the cooling speed with respect to the speed of the growth of the crystal. The periodic doping can be varied also by selection of the rate of cooling by selection of speed of rotation and by excentricity of the crystal pulled from a melt or by growing the crystal with a spiraling growth.
A semiconductor laser diode for an injection laser, said diode having a pn junction formed by a p doped and n doped layers and having a lower threshold value for the diode current and being capable of continuous operation at room temperature and above, the improvement comprising one of the layers in the radiation producing range of the pn junction having a variation in the concentration of the doping with the variation having a spatial periodicity with a maximum concentration of the doping having a range of about 1016 to 1020 parts per cubic centimeter, with a ratio of the maximum concentration to minimum concentration of the doping of at least 2:1 and the maxima of concentration of the doping having a distance of an order of between 10 to 500 atomic distances in the lattice of the crystal, said variations in the concentration of the doping providing at least one interference band in the forbidden band adjacent an edge of one oF the conduction and valence bands and the doping substance being selected in such a way so that the transition probability for transition from the conduction or valence bands respectively to the interference band or bands is essentially larger than for inter-band recombination.
Claim 2
Dependent Claim
205 words
A semiconductor laser diode for an injection laser, said diode having a pn junction formed by a p doped and n doped layers and having a lower threshold value for the diode current and being capable of continuous operation at room temperature and above, the improvement comprising one of the layers in the radiation producing range of the pn junction having a variation in the concentration of the doping with the variation having a spatial periodicity with a maximum concentration of the doping having a range of about 1016 to 1020 parts per cubic centimeter, with a ratio of the maximum concentration to minimum concentration of the doping of at least 2:1 and the maxima of concentration of the doping having a distance of an order of between 10 to 500 atomic distances in the lattice of the crystal, said variations in the concentration of the doping providing at least one interference band in the forbidden band adjacent an edge of one oF the conduction and valence bands and the doping substance being selected in such a way so that the transition probability for transition from the conduction or valence bands respectively to the interference band or bands is essentially larger than for inter-band recombination.
Claim 3
Dependent Claim
27 words
A semiconductor laser diode according to claim 1, wherein the maximum concentration of the doping lies in spaced planes which are directed vertically to the pn junction.
Claim 4
Dependent Claim
28 words
A semiconductor laser diode according to claim 1, characterized in that the maximum concentration of doping is in a range of 1018 to 1020 parts per cubic centimeter.
Claim 5
Dependent Claim
21 words
A semiconductor laser diode according to claim, 1 wherein the ratio of maximum concentration to minimum concentration is more than 10:1.
Claim 6
Dependent Claim
40 words
A semiconductor laser diode according to claim 1, having a pair of interference bands with one band being close to the edge of the conduction band and the other interference band being close to the edge of the valence band.