DE3713045A1 - Method for producing a laser diode having a buried active layer and lateral current limiting, and a laser diode having a buried active layer and lateral current limiting - Google Patents

Abstract

Laser diodes which are produced in only one epitaxial step have a longer life than those which are produced in a plurality of epitaxial steps with intermediate etching steps. Since the double heterostructure for laser diodes having a buried active layer is produced in only one epitaxial step, such that the active layer (33) grows in an interrupted manner by influencing the growth parameters, lateral layers (332) of the same material are produced on the side of the stripe (331) of the active layer (33), and the current must therefore be limited to the region of the stripe (331) of the active layer (33). This lateral current limiting is implemented by means of lateral channels (3322) between the buffer layer (32) and the semiconductor layer (34) on the side of the stripe (331) of the active layer (33). The lateral channels (3322) are produced by partially etching away the lateral layers (332) of the active layer (33), using an acid which attacks only the active layer (33) and leaves the buffer layer (32) and the semiconductor layer (34) undamaged, via transverse channels (341) running at right angles to the layer structure. <IMAGE>

Description

Process for producing a buried laser diode active layer and lateral current limitation and laser diode with buried active layer and lateral current limitation

The invention relates to a method for producing a Laser diode with buried active layer and side Current limitation and a laser diode with buried active Layer and side current limit.

It is known (see e.g. G. Winstel, C. Weyrich, Optoelek tronik 1, Springer Verlag, Berlin, Heidelberg, New York 1980, Pages 225 to 232), laser diodes with low threshold current, high differential efficiency and high output power as a buried double heterostructure laser (burried hetero structure laser, BH laser). The dispute fen-shaped active layer in a semiconductor material with ge lower refractive index and larger energy band gap embedded. The operating chips differ in the operation of the laser diode of the hetero-p-n transition of the laser strip and the lateral homo-p-n transitions because of the different Energy band gaps so that the current is essentially on the The area of the laser strip is limited.

BH laser diodes can be used in multiple epitaxial steps intermediate structuring steps or in just an epitaxial step using structured substrates getting produced. When manufacturing in multiple epitaxy the interfaces that are caused by epitaxy in ge separate processes with intermediate structuring arise, such as B. the interfaces of the laser strip in impaired their quality. The limited lifespan of Laser diodes in the long-wave range, the z. B. in the system InGaAsP / InP are mainly produced on the poor quality of the interfaces. For this Basically, it is recommended to use BH laser diodes in just one epi manufacture taxis step.  

When producing BH laser diodes in just one epitaxy The layers of the various semiconductors become step materials grown on a structured substrate. The growth occurs when the active layer grows parameter chosen so that the active layer on the structure and next to the structure, but not on the flanks of the structure tur grows up. The strip-shaped active layer is then from the semiconductor material with a lower refractive index and larger Energy band gap completely surrounded. In addition to the stripe-shaped active layer grow from it through narrow strips of embedding semiconductor material separately, large-scale layer th of the material of the active layer. The current can be therefore not by simply taking advantage of the different Energy band gaps on the strip-shaped, active layer limit. In this case there are additional ones to limit the current Measures required.

It is known to limit the current in BH laser diodes used in an epitaxial step are produced, thereby realize that p-n transitions to the side of the laser strip will create the reverse operation of the laser diode are poled. (See, e.g., M. Sugimoto et al, Journal of lightwave technology, Vol.LT-2, No. 4, August 1984, page 496 ff.) The p-n junctions are produced by sub strat surface is locally doped or that since Lich the active stripe the differently doped halves conductor layers are grown selectively epitaxially. The laser diode is placed on a semi-insulating substrate builds, d. H. on a substrate made of a semiconductor material high resistivity, is making p-n-over not possible by redoping the substrate surface. The selective epitaxial growth of the differently endowed Semiconductor layers on the side of the active strip required the exact observance of structure and process parameters. The Current limitation by blocking during operation of the laser diode p-n transitions generally have the disadvantage that blocking p-n junctions additional capacities in the laser structure introduce that affect the modulation behavior of the laser diode pregnant.

The invention has for its object an improved Process for producing a buried laser diode active layer and lateral current limit and a laser diode with buried active layer and lateral Strombe boundary that is suitable for both contacts on the substrate to bear opposite side of the layer structure.

The task is carried out using a method based on the generic term of Claim 1 solved according to the invention, as in the characterizing Part of claim 1 is specified. The second part of the task is with a laser diode according to the preamble of claim 26 solved according to the invention, as in the characterizing part of Claim 26 is specified.

In the procedure, the laser diode is in only one epitaxy step, which is beneficial in terms of Life of the laser diode is. The side current limit is through lateral channels laterally from the active layer realized, which has the advantage that no additional Lichen parasitic capacities introduced into the laser structure will.

The method of claim 10 offers the advantage that the lateral channels one by structuring the substrate have a defined shape and that is why the laser diode in repro inducible shape can be produced.

The structure of the laser diode on semi-insulating semiconductor Material according to claim 15 allows both metal contacts Laser diode on the side of the layer facing away from the substrate to build up what the integration of the laser diode in larger building blocks easier.

The application of a stripe-shaped, highly doped layer above the strip of active layer according to claim 18 and an insulator layer outside the strip of the active Layer according to claim 19 improves the lateral current limits tongue.  

Further refinements of the invention result from the rest Claims.

Embodiments of the invention 1 are shown in FIG. To FIG. 5 is provided and will be explained in more detail below.

Fig. 1 shows a double heterostructure on a substrate with a convex structure before etching of the lateral channels.

FIG. 2 shows a double heterolayer structure on a substrate with a concave structure before the etching of the lateral channels.

Fig. 3 shows a laser diode having lateral channels on a substrate of highly conductive material with a convex structure.

FIG. 4 shows a laser diode with lateral channels on a substrate made of highly conductive material with convex structures in the middle and on the edges parallel to it.

Fig. 5 shows a laser diode having lateral channels on a substrate of semi-insulating material having convexes in the center and at the edges parallel thereto.

On a substrate 11 made of a highly conductive semiconductor material such. B. n-doped InP or from a semi-insulating the semiconductor material, ie a semiconductor material with a high specific resistance, a strip-shaped, convex structure extending over the center thereof is produced by etching ( FIG. 1). On the structured surface of the substrate 11 , a buffer layer 12 is epitaxially grown, the type of a first semiconductor material of a first conductivity, for. B. consists of n-doped InP. The structure remains essentially unchanged. An active layer 13 is epitaxially grown on the buffer layer 12 . The active layer 13 consists of a second semiconductor material with a lower energy band gap and a larger refractive index than the material of the buffer layer 12 , for. B. from InGaAsP. The dimensions and shape of the substrate structure are selected such that, with appropriate selection of the process parameters, the active layer 13 only grows as lateral layers 132 next to the structure and as strips 131 on the structure of the substrate 11 . There is an area on the flanks of the structure in which the buffer layer 12 is not covered by the active layer 13 . The side layers 132 of the active layer 13 are not connected to the strip 131 of the active layer 13 . Both in gas phase epitaxy and molecular beam epitaxy as well as in liquid phase epitaxy, it is possible to choose the growth parameters so that the active layer 13 grows as shown above.

On the active layer 13 , a semiconductor layer 14 is epitaxially made of the first semiconductor material of a second conductivity type, for. B. p-doped InP. The surfaces of the active layer 13 and the buffer layer 12 are completely covered. As a result, the strip 131 of the active layer 13 is embedded in the first semiconductor material with a larger energy band gap and a smaller refractive index than the second semiconductor material. On the semiconductor layer 14 , a further semiconductor layer 15 is applied and etched in a strip shape with the aid of a mask so that it extends above the strip 131 of the active layer 13 . The further semiconductor layer 15 is selected so that it reduces the transition resistance in the region of the strip 131 of the active layer 13 .

FIG. 2 shows another exemplary embodiment for the construction of a double heterostructure on a second substrate 21 with a concave structure. The second substrate 21 speaks to the substrate 11 and is made of the same material. On the second substrate 21 is a strip-shaped concave structure, z. B. creates a V-groove. A second buffer layer 22 , which consists of the same material as the buffer layer 12 , is epitaxially grown on the structured surface of the second substrate 21 . When the second buffer layer 22 grows, the profile of the concave structure is lubricated, but the structure also remains concave in a weakened form. A second active layer 23 made of the same material as the active layer 13 is epitaxially grown on the second buffer layer 22 . The growth parameters are selected such that the second active layer 23 grows as the second lateral layers 232 outside the concave structure and as the second stripe 231 in the concave structure. The second side layers 232 and the second strip 231 are not in communication with each other. On the second active layer 23 , a second semiconductor layer 24 is grown, which speaks to the semiconductor layer 14 ent. After this growth, the second strip 231 of the second active layer 23 is completely embedded in the first semiconductor material with the larger energy band gap and the lower refractive index than the second semiconductor material. To improve the contacting properties, a second further semiconductor layer 25 , which corresponds to the further semiconductor layer 15, is applied to the second semiconductor layer 24 . By side etching it is shaped into strips so that it runs above the second strip 231 of the second active layer 23 and that it improves the transition resistance in this area.

The further process steps in the manufacture of a laser diode are explained with reference to FIG. 3. The starting point is a double heterostructure on a third substrate 31 with a convex structure. The double heterostructure contains on the third sub strate 31 , which is made of a highly conductive semiconductor material, such as. B. n-doped InP, there is a third buffer layer 32 , which corresponds to the buffer layer 12 , a third active layer 33 , which corresponds to the active layer 13 , a third semiconductor layer 34 , which corresponds to the semiconductor layer 14 , and a third further semiconductor layer 35, the conductor layer of the other half corresponds to 15 and which, as the further semiconductor layer 15 is stripe-shaped. The double heterostructure is produced by the method that he explained above with reference to FIG. 1. In particular, the third active layer 33 grows subdivided into a third strip 331 and into third layers 332 .

After all layers of the layer structure have been grown in an epitaxy step in liquid phase, gas phase or molecular beam epitaxy, in the next step transverse channels 341 are etched into the third semiconductor layer 34 with the aid of a mask. The transverse channels 341 are etched into the third semiconductor layer 34 such that they run outside the third further semiconductor layer 35 and the third strip 331 of the third active layer 33 perpendicular to the layer structure, at least as far as the third lateral layers 332 of the active layer 33 . The transversal channels 341 can also be etched into the third buffer layer 32 . The transverse channels 341 can be etched wet chemically or by ion etching. Through the transverse channels 341 by partially etching out the third active layer 33 with a selectively active acid which only dissolves the material of the third active layer 33 and which does not attack the material of the third buffer layer 32 and the third semiconductor layer 34 , to the side of the third strip 331 of the third active layer 33 produces lateral channels 3322 . The third lateral layers 332 of the third active layer 33 are etched out to such an extent that the third buffer layer 32 is completely exposed on the flanks of the convex structure and partially outside the region of the structure. At the edges of the double heterostructure, which are further away from the third strip 331 of the third active layer 33 , the originally grown layer sequence remains stable. The residues of the third lateral layers 332 of the third active layer 33 remaining there form webs 3321 . The width of the webs 3321 is determined by the etching time.

To avoid surface currents and to protect the semiconductor surfaces from mechanical damage, it is advantageous to cover the walls of the lateral channels 3322 and the walls of the transverse channels 341 with an electrically insulating material, e.g. B. with SiO₂, Al₂O₃ o. Ä. To coat. It is possible to fill the lateral channels 3322 and the transverse channels 341 with the electrically insulating material.

Finally, a large-area metal contact 36 is brought up on the side of the third substrate 31 facing away from the layer structure. On the side facing away from the third substrate 31 of the layer structure, a structured metal contact 37 is brought up. The structured metal contact 37 has cutouts for the transverse channels 341 and is designed in such a way that the laser diode can be contacted at the side of the region of the third strip 331 of the third active layer 33 . It has been found that it has an unfavorable effect on the operating behavior of the laser diode if the laser diode is contacted above half of the third strip 331 of the third active layer 33 .

An embodiment of the method will be described with reference to FIG. 4, which allows a highly reproducible production of the laser diode.

A fourth substrate 41 is structured by etching using appropriate masks in such a way that a strip-shaped, convex structure extends over the center thereof and that strip-shaped elevations are present on the edges of the fourth substrate 41 parallel to it. The fourth substrate 41 consists of a highly conductive semiconductor material such as. B. n-doped InP. On the fourth substrate 41 , a fourth buffer layer 42 is grown epitaxially, which speaks to the buffer layer 12 ent. On the fourth buffer layer 42 , a fourth active layer 43 , which speaks to the active layer 13 , is grown epitaxially. The growth parameters are selected so that the fourth active layer 43 grows intermittently on the fourth buffer layer 42 . The fourth active layer 43 only grows on the convex structure as the fourth strip 431 and on the side elevations as the lateral webs 433 and between the structures as the fourth lateral layers 432 . The fourth side layers 432 are neither connected to the fourth strip 431 nor to the side webs 433 . The fourth active layer 43 and the exposed parts of the fourth buffer layer 42 are overgrown with a fourth semiconductor layer 44 , which corresponds to the semiconductor layer 14 . After this step, the fourth strip 431 is completely embedded in the first semiconductor material with a lower refractive index and a larger energy band gap than the second semiconductor material. A further semiconductor layer 45 is applied above the fourth strip 431 , which is strip-shaped and which speaks to the further semiconductor layer 15 . It is applied to improve the contact properties in the area of the fourth strip 431 .

Using a mask, analogous to the transverse channels 341 in the fourth semiconductor layer 44 above the lateral layers 432 perpendicular to the layer structure, second transverse channels 441 are etched at least as far as the fourth lateral layers 432 and at most into the fourth buffer layer 42 . The second transverse channels 441 are produced by wet chemical etching or by ion etching. Through the second transverse channels 441 , the fourth lateral layers 432 are etched out with a selectively active acid which only dissolves the second semiconductor material of the fourth active layer 43 and which leaves the fourth buffer layer 42 and the fourth semiconductor layer 44 intact. Instead of the lateral layers 432, lateral channels are created analogously to the lateral channels 3322 .

As in the exemplary embodiment described with reference to FIG. 3, in order to avoid surface currents and to protect the semiconductor surfaces, it is advantageous to cover the walls of the side channels formed by etching out the fourth side layers 432 and the walls of the second transverse channels with the electrically insulating material, for . B. SiO₂, Al₂O₃ or the like, to coat or fill the channels with the electrically insulating material.

Finally, the laser diode on the side facing away from the layer structure of the fourth substrate 41 with a second large-area metal contact 46 corresponding to the large-area metal contact 36 and on the side of the layer structure facing away from the fourth substrate 41 with a second structured metal contact 47 corresponding to the structured metal contact 37 provided.

Another variant of the manufacturing method is described with reference to FIG. 5.

A fifth substrate 51 consisting of a semi-insulating semiconductor material, ie of a semiconductor material with a high specific resistance, is structured by etching accordingly the fourth substrate 41 so that a convex strip runs across the center thereof and that on the parallel edges of the fifth substrate 51 strip-like elevations are present. A fifth buffer layer 52 , which consists of the material of the buffer layer 12, is grown on the fifth substrate 51 . A fifth active layer 53, analogous to the fourth active layer 43 , is grown intermittently on the fifth buffer layer 52 . The growth parameters of the liquid phase or gas phase epitaxy are chosen such that the fifth active layer 53 acts as the fifth stripe 531 on the convex stripe of the fifth substrate 51 , as the second lateral webs 533 on the stripe-shaped elevations of the fifth substrate 51 and as the fifth lateral layers 532 between the structures of the fifth substrate 51 grows. The fifth side layers 532 are not connected to either the fifth strip 531 or the second side web 533 . The material of the fifth active layer 53 is that of the active layer 13 . A fifth semiconductor layer 54 , which corresponds to the semiconductor layer 14, is applied to the fifth active layer 53 . The fifth strip 531 is thus completely embedded in the first semiconductor material with a larger energy band gap and a lower refractive index than the second semiconductor material. Corresponding to the further semiconductor layer 15 , a strip-shaped fifth further semiconductor layer 55 is applied above the fifth strip 531 to improve the contact properties. In the next step, with the help of a mask on one side of the fifth strip 531 above the fifth right lateral layer 5321 , third transverse channels 541 running perpendicular to the layer structure, corresponding to the second transverse channels 441 , into the fifth semiconductor layer 54 at least except for the fifth right side layer 5321 and etched at most into the fifth buffer layer 52 . The mask is designed such that on the other side of the fifth strip 531 above the fifth left side layer 5322 along a line that runs parallel to the fifth strip 531 , the fifth semiconductor layer 54 is etched away. The etching away of the fifth semiconductor layer 54 is continued at least up to the fifth active layer 53 and at most up to the fifth buffer layer 52 . With a selectively effective acid that leaves the first semiconductor material of the fifth buffer layer 52 and the fifth semiconductor layer 54 intact while dissolving the second semiconductor material of the fifth active layer 53 , the fifth right lateral layer 5321 is etched away by the third transverse channels 54 . On the other side of the fifth strip 531 , the fifth left-hand side layer 5322 and, if still present, the second side-side web 533 are etched away with the selectively active acid, so that the fifth buffer layer 52 on this side is exposed to the edge.

Finally, the laser diode is provided with metal contacts. A first metal contact 56 is applied directly to the fifth buffer layer 52 on the side of the fifth strip 531 on which the fifth semiconductor layer 54 has been removed. A second metal contact 57 is applied to the remaining fifth semiconductor layer 54 and to the fifth further semiconductor layer 55 . The second metal contact 57 is structured in such a way that the third transverse channels 541 remain open and that the laser diode can be contacted outside the region of the fifth strip 531 .

Analogous to what has been described above, in order to avoid surface currents and to protect the semiconductor surfaces, it is expedient to use the electrically insulating material to expose exposed semiconductor surfaces, as occur on the third transverse channels 541 and on the channels formed by etching out the fifth lateral layers 532 , e.g. B. SiO₂, Al₂O₃ or the like, to coat or fill the channels with the electrically insulating material.

The laser diode produced in this method is contacted from only one side, from above, since the fifth substrate 51 has a high specific resistance.

Claims (27)

1. A method for producing a laser diode with lateral current supply and buried active layer between a buffer layer and a semiconductor layer and two metal contacts, characterized in that the laser diode in an epitaxial step on a sub strat ( 11 , 21 , 31 , 41 , 51 ) and that between the buffer layer ( 12 , 22 , 32 , 42 , 52 ) and the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) to the side of the active layer ( 13 , 23 , 33 , 43 , 53 ) lateral channels ( 3322 ). 2. The method according to claim 1, characterized in that the substrate ( 11 , 21 , 31 , 41 , 51 ) is structured on a surface. 3. The method according to claim 2, characterized in that the substrate ( 11 , 21 , 31 , 41 , 51 ) is structured such that a convex strip extends within the substrate ( 11 , 21 , 31 , 41 , 51 ). 4. The method according to claim 2, characterized in that the substrate ( 11 , 21 , 31 , 41 , 51 ) is structured such that a concave strip runs within the substrate ( 11 , 21 , 31 , 41 , 51 ). 5. The method according to claim 3 or 4, characterized in that on both sides of the strip within the substrate ( 11 , 21 , 31 , 41 , 51 ) parallel to the strip concave structures are generated, which are not in connection with the stiffener. 6. The method according to claim 3 or 4, characterized in that on both sides of the strip within the substrate ( 11 , 21 , 31 , 41 , 51 ) to the strip parallel, convex structures are generated, which are not connected to the strip connec tion. 7. The method according to any one of claims 1 to 6, characterized in that with the aid of a mask perpendicular to the layer structure to the side of the active layer ( 13 , 23 , 33 , 43 , 53 ) transverse channels ( 341 , 441 , 541 ) in the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) are etched down to the lateral channels ( 3322 ). 8. The method according to any one of claims 2 to 7, characterized by the following steps:

• a. on the structured substrate ( 11 , 21 , 31 , 41 , 51 ) are successively epitaxially the buffer layer ( 12 , 22 , 32 , 42 , 52 ), the active layer ( 13 , 23 , 33 , 43 , 53 ) and the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) applied,
• b. the process parameters when growing the active layer ( 13 , 23 , 33 , 43 , 53 ) are chosen so that the active layer ( 13 , 23 , 33 , 43 , 53 ) only grows on the structure and next to the structure and that the active Layer ( 13 , 23 , 33 , 43 , 53 ) does not grow on the flanks of the structure,
• c. With the aid of a mask, the active layer ( 13 , 23 , 33 , 43 , 53 ) is inserted into the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) perpendicular to the layer structure outside the middle strip ( 131 , 231 , 331 , 431 , 531 ) ) the transverse channels ( 341 , 441 , 541 ) are etched at least down to the lateral layers ( 132 , 232 , 332 , 432 , 532 ) of the active layer ( 13 , 23 , 33 , 43 , 53 ),
• d. with a selectively active acid, which only attacks the material of the active layer ( 13 , 23 , 33 , 43 , 53 ) and the material of the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) and the buffer layer ( 12 , 22 , 32 , 42 , 52 ) does not attack, the lateral layers ( 132 , 232 , 332 , 432 , 532 ) of the active layer ( 13 , 23 , 33 , 43 , 53 ) are etched away, thereby creating the lateral channels ( 3322 ).

9. The method according to claim 8, characterized in that the lateral extent of the lateral channels ( 3322 ) is determined by a time limit of the etching process. 10. The method according to any one of claims 2 to 8, characterized in that the lateral extent of the lateral channels ( 3322 ) by lateral structures of the sub strate ( 41 , 51 ), on the flanks of which the active layer ( 43 , 53 ) does not grow and on the flanks of which the etching process is therefore ended is determined. 11. The method according to any one of claims 7 to 10, characterized in that the transverse channels ( 341 , 441 , 541 ) are etched into the buffer layer ( 12 , 22 , 32 , 42 , 52 ). 12. The method according to any one of claims 7 to 11, characterized in that the etching of the transverse channels ( 341 , 441 , 541 ) is carried out wet-chemically. 13. The method according to any one of claims 7 to 11, characterized in that the etching of the transver salen channels ( 341 , 441 , 541 ) is carried out by ion etching. 14. The method according to any one of claims 1 to 13, characterized in that the laser structure on a substrate ( 11 , 21 , 31 , 41 ) is grown from a highly conductive semiconductor material and that one of the two metal contacts on the substrate ( 11 , 21 , 31 , 41 ) facing away from the layer structure and the other of the two metal contacts on the side facing away from the layer structure of the substrate ( 11 , 21 , 31 , 41 ) are applied. 15. The method according to any one of claims 1 to 13, characterized in that the laser structure is grown on a substrate ( 51 ) made of a semi-insulating semiconductor material and that the two metal contacts ( 56 , 57 ) on the side of the layer facing away from the substrate ( 51 ) be applied. 16. The method according to claim 15, characterized in that the strip ( 531 ) of the active layer ( 53 ) contains the semiconductor layer ( 54 ) and the active layer ( 53 ) except for the buffer layer (on one side of the strip-shaped structure) 52 ) are removed and that one of the metal contacts ( 56 ) is applied to the exposed buffer layer ( 52 ). 17. The method according to claim 16, characterized in that the mask for etching the transverse channels ( 541 ) is designed so that in the same operation in which the transverse channels ( 541 ) are produced by etching, on one side of the strip ( 531 ) of the active layer ( 53 ) the semiconductor layer ( 54 ) is removed at least down to the active layer ( 53 ) by etching. 18. The method according to claim 17, characterized in that the semiconductor layer ( 54 ) and the active layer ( 53 ) up to the buffer layer ( 52 ) are removed by etching. 19. The method according to any one of claims 1 to 18, characterized in that to improve the transition resistance in the region of the laser resonator on the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) a further semiconductor layer ( 15 , 25 , 35 , 45 , 55 ) is applied and that the further semiconductor layer ( 15 , 25 , 35 , 45 , 55 ) is brought into strip form by etching in such a way that the strip ( 131 , 231 , 331 , 431 , 531 ) of the active layer ( 13 , 23 , 33 , 43 , 53 ) lies in the shadow. 20. The method according to any one of claims 1 to 19, characterized in that outside the region of the strip ( 131 , 231 , 331 , 431 , 531 ) of the active layer ( 13 , 23 , 33 , 43 , 53 ) on the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) an insulator layer is applied. 21. The method according to any one of claims 1 to 20, characterized in that the buffer layer ( 12 , 22 , 32 , 42 , 52 ), the active layer ( 13 , 23 , 33 , 43 , 53 ) and the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) are applied to the substrate ( 11 , 21 , 31 , 41 , 51 ) by liquid phase epitaxy. 22. The method according to any one of claims 1 to 20, characterized in that the buffer layer ( 12 , 22 , 32 , 42 , 52 ), the active layer ( 13 , 23 , 33 , 43 , 53 ) and the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) are applied to the substrate ( 11 , 21 , 31 , 41 , 51 ) by gas phase epitaxy. 23. The method according to any one of claims 1 to 20, characterized in that the buffer layer ( 12 , 22 , 32, 42, 52 ), the active layer ( 13 , 23 , 33 , 43 , 53 ) and the semiconductor layer ( 14 , 24 , 34 , 44 , 54 ) are applied to the substrate ( 11 , 21 , 31 , 41 , 51 ) by molecular beam epitaxy. 24. The method according to any one of claims 1 to 23, characterized in that the walls of the lateral channels ( 3322 ) and the transverse channels ( 341 , 441 , 541 ) are coated with an electrically insulating material. 25. The method according to any one of claims 1 to 23, characterized in that the lateral channels ( 3322 ) and the transverse channels ( 341 , 441 , 541 ) are filled with an electrically insulating material. 26. Laser diode with lateral current limitation and buried active layer between a buffer layer and a semiconductor layer and two metal contacts, characterized by the following features:

• a. the buffer layer ( 52 ) made of highly conductive semiconductor material was grown on a substrate ( 51 ) made of semi-insulating semiconductor material, ie semiconductor material with a high specific resistance,
• b. the semiconductor layer ( 54 ), the active layer ( 53 ) and the buffer layer ( 52 ) are grown in an epitaxial step on the substrate ( 51 ),
• c. Lateral channels are provided between the buffer layer ( 52 ) and the semiconductor layer ( 54 ) to the side of the active layer ( 53 ) to limit the current.
• d. a first metal contact ( 56 ) is applied directly on the buffer layer ( 52 ) outside the region of the active layer ( 53 ) and the lateral channels,
• e. a second metal contact ( 57 ) is applied to the semiconductor layer ( 54 ).

27. Laser diode manufactured according to one of the methods Claims 1 to 25.