DE10039435A1 - Radiation-emitting semiconductor component used as an illuminating diode or semiconductor laser comprises an active layer, a contact surface and a cylindrical semiconductor body - Google Patents

Abstract

Radiation-emitting semiconductor component comprises an active layer (11), a contact surface (12) and a cylindrical semiconductor body (8). The active layer is arranged vertically to the cylindrical axis (10) and the radiation generated during operation is emitted partially vertical to the cylindrical axis. During operation a first region (4) and a second region (5) are formed in the plane of the active layer so that radiation is only produced in the first region and the first region is surrounded by the second region. An Independent claim is also included for a process for the production of the radiation-emitting semiconductor component comprising forming the active layer which extends over the cross-sectional surface of the semiconductor body, and mixing the parts of the active layer corresponding to the second region by diffusion or implantation so that no radiation is produced in the mixed region. Preferred Features: The semiconductor body contains GaAs, AlGaAs, AlGaSb, AlGaAsPb, InGaASP, InP or GaSb.

Description

The invention relates to a radiation-emitting semi-lead terbauelement according to the preamble of claim 1 so like a manufacturing process for this.

With radiation-emitting semiconductor components, such as for example, light emitting diodes or semiconductor lasers well known problem in that due to total reflection xion a large part of the radiation generated in the semiconductor body remains and is not decoupled. The through total reflection Coupling losses caused by xion depend, among other things, on the shape of the semiconductor body and the semiconductor material.

Materia has a particularly high decoupling loss lines based on GaAs or GaN and a high bre own index. A high refractive index leads to one small total reflection angle (based on the normal of the reflective surface) and thus to a small extent degree of coupling, since only the radiation components are decoupled the one that falls onto the decoupling surface at an angle len, which is smaller than the total reflection angle.

For cylindrical components with predominantly lateral emis direction (perpendicular to the longitudinal axis of the cylinder) the To Valley reflection problem further exacerbated because of the cylinder jacket acts as a totally reflective ring resonator and with high Efficiency prevents the generated radiation from being decoupled.

Cylindrical components with lateral emission direction represent, for example, microcavity lasers, which from US 5,825,799 are known.  

A cylindrical semiconductor body is shown here an active layer sequence, with the individual layer levels are arranged perpendicular to the cylinder longitudinal axis. The generate Laser radiation propagates in the layer plane and is coupled out via neighboring structures. The coupling between the laser-active layer and the decoupling structures is based on the resonant tunnel effect.

Such additional decoupling structures cause the production of additional effort and must with high Precision can be aimed at the laser-active layers. Furthermore, such structures are based on certain types of lasers limits.

The invention is based, a lateral beam to create lung-emitting semiconductor device, the one has increased radiation yield and at the same time simple and is inexpensive to manufacture.

Furthermore, it is an object of the present invention, a Her procedures for this.

This task is accomplished by a radiation-emitting semi-lead terbauelement according to claim 1 or by a Manufacturing method according to one of claims 13 to 18 solved. Advantageous developments of the invention are Subject of subclaims 2 to 12 and 19.

According to the invention, the semiconductor body of the radiation-emitting semiconductor component cylindrically shape, with the active layer perpendicular to the cylinder lengthways axis is arranged and the radiation generated during operation at least partially perpendicular to the longitudinal axis of the cylinder is tiert. Under a cylindrical body is ne ben a circular cylinder generally a body with coincident to understand mender base and top surface, for example a Cylinder with an ellipse or an oval as the base and Cover surface.  

A first region is formed in the active layer, in which is generated by electromagnetic radiation.

This first area is surrounded by a second area that is radiation inactive. Under radiation inactive is here to understand that there is no radiation in this area creates or amplifies or that radiation generation or reinforcement to a much lesser extent than in the first Area takes place.

Accordingly, the second area is for those in the first area generated radiation transparent or to a certain extent Degrees absorbent.

This arrangement causes the proportion of radiation that is below a larger angle than the total reflection angle on the Cylinder surface hits, is reduced and that a multiple, cyclical total reflection on the cylinder surface che is suppressed. The total reflections are thus advantageous xions losses reduced.

In a particularly preferred development of the invention the semiconductor body is designed as a semiconductor laser. because at forms the cylindrical surface of the semiconductor body Laser resonator, so that the laser radiation generated lower is emitted right to the cylinder longitudinal axis.

A first area is again formed in the active layer forms, which is surrounded by a second region, the stimulated emission essentially takes place in the first area place.

This arrangement advantageously suppresses training undesirable, because ring modes are difficult to decouple in the laser sonator.  

An advantageous development of the invention consists in the semiconductor body or the resonator as a circle training cylinders.

In the case of circular cylindrical semiconductor bodies, the high rotational symmetry particularly easy cyclic multiple total reflections or ring modes arise, so that their suppression by the invention is particularly important here is a big advantage.

In a preferred embodiment of the invention, it is most radiation generating or amplifying area shaped. This advantageously makes it a radially homogeneous one ne luminance achieved.

A particularly preferred development of the invention exists in making the first area circular and concentric to the To arrange the cylinder longitudinal axis.

In the case of circular cylinders, the rotati is below the cylinder's longitudinal axis to understand axis of symmetry, with cylinders with other Cross section the axis running parallel to the lateral surface by the focus of the cross-sectional area. It is an advantage so the first, radiation active area evenly from the Shell surface spaced, so that an efficient suppress ring mode is guaranteed.

In the invention, the active layer is preferably as Single quantum well (SQW, single quantum well) or multiple quantum well (MQW, multiple quantum well) executed. This Layer structures allow the construction of highly efficient La with low threshold current density.

Quantum well structures can be preferred by layering implement systems based on GaAs. Are suitable as material in particular, in addition to GaAs, the ternaries or quaternary mixing systems AlGaAs, AlGaSb, AlGaAsSb, InGaAsP as well as the related compounds such as InP or GaSb.  

The formation of ring modes is of great advantage here prevents that otherwise due to the high refractive index GaAs-based materials can easily arise.

A particularly preferred development of the invention exists in it, on the semiconductor body or in the semiconductor body to form annular insulation layers.

These insulation layers concentrate the current during operation in the center of the active layer, so that the first radiation-emitting or radiation-amplifying area trains while in the peripheral areas of the active layer no electricity is injected. The radiation inak arises there tive, second area surrounding the first area.

The formation of annular insulation structures is at known and established for example from VCSEL technology and can advantageously be used in the present invention be set.

The insulation layers can, for example, by annular oxide layers, semi-insulating semiconductor layer th or ring-shaped pn junctions, which block during operation be educated.

In a further advantageous embodiment of the invention is the active layer itself in the lateral direction Size of the first area. Advantageously, in in this case the size of the first, radiating area of the production can be determined very precisely.

A further preferred embodiment of the invention has a main surface of the cylindrical semiconductor body Contact area whose area is smaller than the cross sectional area of the cylindrical semiconductor body and the im Center of the main surface is formed.  

This contact surface has the advantage that in operation the active layer is energized an area that is about the axial projection of the contact surface onto the active layer corresponds and forms the first area, while in the Edge zone of the active layer no current is injected, so that this edge zone forms the second area.

Alternatively, the contact area can also cover the entire area Main surface of the semiconductor body, wherein between Contact surface and semiconductor body an insulating ring, for example, an oxide ring is formed with the same Effect causes only the center of the active layer is energized.

Both alternatives can be of great advantage to existing ones Semiconductor structures are used because only the au External contact geometry must be changed.

In a preferred manufacturing method for an invent component according to the invention with a ring-shaped insulation This insulation layer becomes layer by selective separation an insulating material.

Another advantageous manufacturing process is in, an annular region of the semiconductor body selective oxidation, ion implantation or diffusion in egg to convert an isolator.

In the case of oxidation, chemical originates from the half a non-conductive oxide. ion implantation leads to a high number of lattice defects in the implant onsbereich, so that the semiconductor due to the deformed Lattice structure acts as an insulator. By diffusion can Use a suitable diffusion material ability of the semiconductor in the diffusion region so far be set that the diffusion area compared to the diffu non-ionic area has an isolating effect. All three procedures often used in the manufacture of semiconductor devices  used and can therefore easily in the manufacturing process of a component according to the invention can be integrated.

In a further preferred production method, the active layer through selective epitaxy in the center of the half conductor body grew up, so that the active layer itself defines the size of the first radiation-active area. In this manufacturing process, it can be advantageous to add steps to form an annular insulation layer to be dispensed with.

In a further manufacturing process is initially in egg In the first step, the active layer over the entire cross section of the semiconductor body formed.

In the next step, the annular edge area becomes this active layer by implantation or diffusion through mixes so that there is essentially no jet in this area generation takes place in the company.

This method is particularly suitable for quantum wells layers due to the extremely thin layer structures easily afterwards by diffusion or implantation degra can be dated.

Further features, advantages and expediencies of the invention are explained below with reference to ten exemplary embodiments in conjunction with FIGS. 1 to 11.

Show it:

Fig. 1 is a schematic sectional view of a first embodiment of a device according to the invention,

Fig. 2 is a schematic sectional view of a second embodiment of a device according to the invention compared to the prior art,

Fig. 3 elements is a schematic, perspective view of egg nes third embodiment of a construction according to the invention,

Fig. 4, the threshold behavior of the first game Ausführungsbei an inventive device in dependence of the size of the first radiation-reinforcing area,

Fig. 5 is a schematic sectional view of a fourth embodiment of a device according to the invention,

Fig. 6 is a schematic sectional view of a fifth embodiment of a device according to the invention,

Fig. 7 is a schematic sectional view of a sixth embodiment of a device according to the invention,

Fig. 8 is a schematic sectional view of a seventh embodiment of a device according to the invention,

Fig. 9 is a schematic sectional view of an eighth embodiment of a device according to the invention,

Fig. 10 is a schematic sectional view of a ninth embodiment of a device according to the invention, and

Fig. 11 is a schematic sectional view of a tenth embodiment of a device according to the invention.

The same or equivalent parts are here with the same Provide reference numerals.

Fig. 1 shows the cross section through the semiconductor body egg nes cylindrical microcavity laser based on GaAs. The Zy longitudinal axis is perpendicular to the cutting plane. The cylindrical surface 1 forms a cylindrical resonator, which is circular in section.

In such a resonator, modes 2 are capable of spreading on the one hand, which run through the center of the resonator and are reflected back on the lateral surface 1 under normal incidence (central modes). When reflecting on the outer surface 1 , part of the radiation is coupled out of the laser resonator.

Ring mode 3 in the form of an equilateral triangle represents another mode that can be propagated. This mode 3 strikes cylinder jacket surface 1 at 30 ° (based on the surface normal at the point of impact).

Since this angle is greater than the total reflection angle, which is 17.6 ° for GaAs against air, the ring mode 3 runs in the resonator with almost no loss under total reflection.

Ring modes of higher order in the form of regular polygons with a higher number of corners are also spreadable. Because of their mode of propagation, ring fashion 3 and higher ring fashions are referred to as "whispering gallery fashions" (WG mode, wispering gallery mode). They have a high circulation gain and can therefore be easily excited.

The formation of such a shared mode is disadvantageous because the degraded modes of WG-population inversion density of the desired central Mode 2 is not longer available, so that the Zen tralmode attenuated 2 or even extinguished.

The invention suppresses an oscillation of these WG modes by the fact that the reinforcing, laser-active first region 4 is formed in the center of the cross-sectional area.

As a result, the overlap between the mode volume and the laser-active area in WG mode 3 is less than in central mode 2 .

Accordingly, the WG mode 3 experiences a lower Umlaufver gain than the central modes 2 , so that preferably the desired and decouplable central modes 2 swings. Since the refractive index of the two areas 4 and 5 is approximately the same, the total reflection angle at this interface is so large that no WG modes can form within the laser-active area 4 .

The direction of the central mode 2 and the WG mode 3 is not fixed due to the rotational symmetry of the resonator. A large number of central modes are therefore formed in different directions during operation. Modes 2 and 3 shown in Fig. 1 are only one possible example.

FIG. 2a shows a cross section corresponding to FIG. 1 through the circular cylindrical semiconductor body of a high-performance LED. For comparison, an LED according to the prior art is shown in FIG. 2b.

In the LED according to the prior art, the active layer is formed continuously over the entire cross section. The laterally emitted radiation generated in the edge layers, shown for example on the basis of the edge region 6 , strikes large parts at such a flat angle on the cylinder surface 1 that these radiation components 7 are totally reflected there. Accordingly, only a small proportion of the radiation generated is coupled out.

The totally reflected radiation component 7 runs under cyclic multiple total reflection in the semiconductor body and thus reduces the radiation yield.

In contrast, in the LED shown in FIG. 2a, the radiation-generating first area 4 is circular and concentric with the cylinder cross-sectional area, the radiation-generating first area 4 being smaller than the cylinder cross-sectional area. The refractive index of the radiation-active region 4 and the radiation-inactive region 5 surrounding it is approximately the same.

By concentrating the generation of radiation on the inner region 4 , the angle of incidence on the cylinder surface 1 is reduced and the proportion of the total reflected radiation is reduced or the radiation yield is increased.

It is particularly advantageous here that the radius ratio according to the formula

to choose, where r denotes the radius of the first region 4 , R the radius of the cross-sectional area, n the refractive index of the semiconductor material and n ₀ the refractive index of the medium surrounding the semiconductor body.

In this geometry, each light beam emitted from the first region 4 strikes the lateral surface 1 at a smaller angle than the total reflection angle, so that no total reflection occurs on the lateral surface.

In Fig. 3, a radiation-emitting semiconductor component is shown in perspective, the cross section of which speaks ent the cross section shown in Fig. 1 or 2a.

The component consists of a circular cylindrical semiconductor body 8 , which is applied to an electrically conductive substrate 9 . On the side facing away from the semiconductor body 8 , the substrate 9 has a contact area 14 .

In the semiconductor body 8 , an active layer or a sequence of active layers 11 is formed perpendicular to the cylinder longitudinal axis 10 , which extends over the entire cross section of the semiconductor body 8 .

On a main surface of the semiconductor cylinder 8 , a circular contact 12 is formed and arranged derquerschnitt concentric to the Zylin. The radius of the contact surface 12 is smaller than the radius of the semiconductor body 8 . In operation, therefore, only a circular area in the center of the active layer is energized. This area forms the radiation-active, first area 4 , since only this area generates radiation or is amplified in a laser, while the outer ring 14 forms the radiation-inactive, second area 5 .

In FIG. 4, for a semiconductor laser with a cross section corresponding to FIG. 1, the threshold gain g _{th is plotted} as a function of the ratio q of the area of the laser-active first region 4 to the total cross-sectional area for the central mode 2 and WG mode 3 modes shown in FIG. 1 ,

The threshold gain of a mode is the gain for the total gain and total loss in a resonator cycle are the same.

The following relationship applies to the threshold gain g _{th of} the central mode 2 :

where r is the radius of the first region 4 , R is the radius of the cross-sectional area, ρ _{Z is} the degree of reflection of the coupling out surfaces and α is the absorption in the radiation-inactive second region.

Without mirroring, the reflectance ρ _Z results from the Fresnel equations for vertical incidence

The refractive index of the semiconductor body is given by n, the refractive index of the surrounding medium by n ₀ .

The following applies accordingly to the threshold gain g _th of WG mode 3 :

Since the WG mode revolves under total reflection, the degree of reflection ρ _{Δ is} almost 100%.

The distance s is a measure of the overlap between the mode volume and the laser-active area. The total length of the portions of WG mode 3 lying within the laser-active area 4 in one revolution is 6s.

The threshold gain is plotted in Fig. 4 for the central 19 Mode 2 and the threshold gain for the WG-20 Mode 3 as a function of the ratio of the surface q of the first region 4 to the cross-sectional area of the semiconductor body. In operation, the mode with the lower threshold gain preferably swings.

As the figure shows, has the central Mode 2 to egg nem area ratio of 0.64 less than the strengthening Schwellenver WG mode 3, and therefore vibrates preferentially to. For an area ratio below 0.25, corresponding to a radial ratio of 0.5, the WG mode no longer overlaps with the gain region 4 , so that in this case the WG mode 3 cannot oscillate.

For radius ratios below 0.5, the threshold gain g _th for WG mode 3 is therefore no longer defined.

A radius ratio of 0.5 is particularly advantageous because of the efficient suppression of WG modes while maximizing the size of the first radiation-active region 4 .

Since higher WG modes propagate closer to the cylinder surface 1 than WG mode 3 , these modes are suppressed even more than WG mode 3 .

In FIG. 5 to 11 seven different realizations of the invention are shown in a sectional view.

The component shown in FIG. 5 corresponds to the embodiment shown in FIG. 3. The applied to a sub strate 9 , cylindrical semiconductor body 8 is provided with a circular contact 12 , the radius of which is smaller than the radius of the semiconductor body. In operation, current 15 is introduced only into the circular center 13 of the active layer 11 and the radiation-active first region 4 is thus formed.

A similar current flow can be achieved with the component shown in FIG. 6. Here, an insulation layer 16 is deposited on the semiconductor body 8 , which covers a main surface of the semiconductor body 8 in an annular manner. On this insulation layer 16 , a contact surface 12 is formed over the entire cross section of the semiconductor component. Into the semiconductor body 8 , current 15 is injected only through the area uncovered by the insulation layer 16 . As described above, therefore, a first radiation-active region 4 is formed only in the center 13 of the active layer 11 .

A further possibility for forming this area 4 is shown in FIG. 7. Here, a ring-shaped insulation layer 17 is introduced in the vicinity of the active layer. The current 15 is likewise concentrated in the center 13 of the active layer 11 through this insulation ring. The insulation ring 17 can be formed by an annular oxide layer, by a ring-shaped, proton-insulated semiconductor layer or a ring-shaped, blocking pn junction.

Alternatively, as shown in FIG. 8, the annular insulation layer 17 can also be deposited directly on the active layer 11 , for example by means of a semi-insulating semiconductor layer or one of the possibilities mentioned above.

The exemplary embodiment shown in FIG. 9 differs from the previous exemplary embodiments in that the active layer 11 is formed only in the center and not over the entire cross section of the semiconductor body. Here, the first radiation-active region 4 is given by the size of the active layer 11 itself, the radiation-inactive region is formed by the semiconductor material laterally surrounding the active layer. Such a laterally delimited active layer can be grown, for example, by means of selective epitaxy.

Another possibility of forming a laterally limited active layer 11 is to first form the active layer 11 over the entire cross section of the semiconductor body 8 and then to treat the edge zone of the active layer 11 in such a way that radiation generation can no longer take place here, Fig. 11. With SQW and MQW structures, this can be done, for example, by diffusion or implantation-induced mixing of the quantum layers.

Another embodiment based on ion implantation or diffusion is shown in FIG. 10. Here, the conductivity of the man layer 18 of the semiconductor body 8 is reduced by proton isolation or diffusion so that only 15 flows through the center of the semiconductor body 8 during operation, and so the radiation-active, first region 4 is formed in the center of the active layer 11 .

The techniques described for training a fiction According semiconductor body are known to those skilled in the art and who often used in the manufacture of semiconductor devices looking. Therefore, the specified embodiments require of a manufacturing method according to the invention more advantageous do not require any special additional effort in the production.

The explanation of the invention with reference to that described above Embodiments are of course not as Be understanding the limitation of the invention. The characteristics of one individual embodiments are not on the respective off example, but can be used as required can also be combined.

Claims (19)

1. Radiation-emitting semiconductor component with an active layer ( 11 ), a contact surface ( 12 ) and a cylindrical semiconductor body ( 8 ), the active layer ( 11 ) being arranged perpendicular to the longitudinal axis of the cylinder ( 10 ) and the radiation generated during operation at least partially is emitted perpendicular to the longitudinal axis of the cylinder ( 10 ), characterized in that a first region ( 4 ) and a second region ( 5 ) are formed in the plane of the active layer ( 11 ) during operation, the radiation essentially only in the first region ( 4 ) it is produced and the first area ( 4 ) is surrounded by the second area ( 5 ). 2. Radiation-emitting semiconductor component according to claim 1, characterized in that the semiconductor body ( 8 ) is designed as a semiconductor laser, the semiconductor body ( 8 ) forming a cylindrical resonator and the laser radiation generated during operation is emitted perpendicular to the longitudinal axis of the cylinder ( 10 ) and the stimulate te Emission essentially takes place in the first area ( 4 ). 3. Radiation-emitting semiconductor component according to claim 1 or 2, characterized in that the semiconductor body ( 8 ) is shaped as a circular cylinder. 4. Radiation-emitting semiconductor component according to one of claims 1 to 3, characterized in that the first region ( 4 ) is circular. 5. Radiation-emitting semiconductor component according to one of claims 1 to 4, characterized in that the first region ( 4 ) is circular and is arranged concentrically to the cylinder longitudinal axis ( 10 ). 6. Radiation-emitting semiconductor component according to one of claims 1 to 5, characterized in that the semiconductor body ( 8 ) contains GaAs, AlGaAs, AlGaSb, AlGaAsSb, In GaAsP, InP or GaSb or a material based thereon. 7. Radiation-emitting semiconductor component according to one of claims 1 to 6, characterized in that in the semiconductor body ( 8 ) at least one insulation ring ( 17 ) is formed, the current ( 15 ) leads to the first loading area ( 4 ) during operation. 8. Radiation-emitting semiconductor component according to claim 7, characterized in that the at least one insulation ring ( 17 ) is formed by a semi-insulating layer with a conductive center, an annular pn junction which blocks operation or an annular oxide layer. 9. Radiation-emitting semiconductor component according to one of claims 1 to 6, characterized in that the lateral extent of the active layer ( 11 ) corresponds to the first region ( 4 ). 10. Radiation-emitting semiconductor component according to one of claims 1 to 6, characterized in that the size of the contact surface ( 12 ) corresponds to the lateral extent of the first region ( 4 ). 11. Radiation-emitting semiconductor component according to one of claims 1 to 6, characterized in that the contact surface ( 12 ) is formed over the entire cross section of the semiconductor body ( 8 ) and between the con tact surface ( 12 ) and the semiconductor body ( 8 ) an insulation ring ( 16 ) is arranged. 12. Radiation-emitting semiconductor component according to claim 11, characterized in that the at least one insulation ring ( 17 ) is formed by a ring-shaped oxide layer. 13. A method for producing a radiation-emitting semiconductor component according to claim 7 or 11, characterized in that the insulation ring ( 16 ), ( 17 ) is formed by deposition of an insulating material. 14. A method for producing a radiation-emitting semiconductor component according to claim 7 or 11, characterized in that the insulation ring ( 16 ), ( 17 ) is formed by selective oxidation of the ring surface. 15. A method for producing a radiation-emitting semiconductor component according to claim 7, characterized in that the isolation ring ( 17 ) is formed by selective ion implantation in the ring area. 16. A method for producing a radiation-emitting semiconductor component according to claim 7, characterized in that the insulation ring ( 17 ) is formed by selective diffusion of a material in the ring area, which reduces the conductivity of the semiconductor body ( 8 ) in this area. 17. A method for producing a radiation-emitting semiconductor component according to claim 9, characterized in that the active layer ( 11 ) is formed by selective epitaxy in the center of the cylindrical semiconductor body. 18. A method for producing a radiation-emitting semiconductor component according to claim 9, characterized by the steps

• - Formation of an active layer ( 11 ) which extends over the entire cross-sectional area of the cylindrical semiconductor body ( 8 ),
• - Mixing the portions of the active layer corresponding to the second region ( 5 ) by diffusion or implantation, so that no radiation is generated in the mixed region during operation.

19. The method according to claim 18, characterized in that the active layer as a single quantum well or multiple quantum tent pot is formed.