Semiconductor epitaxial structure

Abstract

To provide a semiconductor epitaxial structure.SOLUTION: There is provided a semiconductor epitaxial structure including a substrate, a lower Bragg reflection mirror (DBR) layer, an active region, an upper Bragg reflection mirror (DBR) layer, and a light confinement layer. The lower DBR layer is located on the substrate. The active region is located on the lower DBR layer. The upper DBR layer is located on the active region. The light confinement layer is located inside or outside the active region, and the material of the light confinement layer contains a phosphorus (P)-containing compound. The light confinement layer includes an insulation region and a non-insulation region, and the insulation region surrounds the non-insulation region.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to semiconductor epitaxial structures. [Background technology]

[0002] Please refer to Patent Document 1, which the inventor of the present application previously obtained a patent and whose invention title is Vertical Cavity Surface Emitting Laser (VCSEL) with Current Confinement Layer. Patent Document 1 aims to improve the power conversion efficiency (PCE) and optical output, and the technical means is via at least two current confinement layers, and in order to achieve the purpose of improving the PCE of the multi-junction VCSEL, the optical aperture areas on the at least two current confinement layers must be unequal and controlled to be equal to or less than a certain optical aperture area ratio. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Taiwan Patent No. 738388 Summary of the Invention [Problem to be solved by the invention]

[0004] From the contents of Patent Document 1, it can be seen that the inventor of the present invention focused mainly on improving the optical output and energy saving of multi-active layer VCSELs about four years ago (2020). In other words, the demand at that time was to improve the detection distance (optical output) and PCE of "multi-active layer VCSELs". However, whether multi-active layer VCSELs can be widely used in optical communication or optical sensing schemes depends on the size of the divergence angle of the VCSEL, that is, the smaller the divergence angle of the VCSEL, the better.

[0005] Patent Document 1 adopted technical means at that time of at least two current confinement layers with unequal optical aperture areas, some schemes in Patent Document 1 have too large divergence angles (e.g. AlGaAs current confinement layers), while some other schemes have not too large divergence angles (e.g. AlAs current confinement layers), but these schemes have some necessary restrictions, such as a multi-layered VCSEL must use at least two current confinement layers, and the optical aperture sizes of the at least two current confinement layers must also be different. Ideally, the difference in the optical aperture sizes of the at least two current confinement layers in different (lot) VCSELs should be consistent.

[0006] In the technical field to which the present application pertains, the method of making the sizes of the optical apertures of the two current confinement layers obviously different is to oxidize the two current confinement layers at different oxidation rates during oxidation, for example, to use different compounds or the same compound with different material component ratios for the two current confinement layers. In fact, the actual oxidation rates of the two current confinement layers are necessarily different from the predetermined oxidation rate, and even if different lots of VCSELs are continuously subjected to oxidation treatment on the same machine, the oxidation rates of the different lots of VCSELs are different, so the sizes or shapes of the optical apertures of each (lot) of VCSELs are inevitably different from each other. In particular, the oxidation rate of some compounds is too fast, so the sizes or shapes of the optical apertures of each (lot) of VCSELs are significantly different from each other, resulting in low uniformity.

[0007] However, as can be seen from several of the embodiments and experimental results recited herein, the present invention can actually provide a multi-active layer VCSEL with a small divergence angle and a consistent optical aperture size or shape for each (lot) of VCSELs using only a single optical confinement layer (rather than the need for at least two optical confinement layers).

[0008] More specifically, the technical problems and requirements that Patent Document 1 actually aims to solve are unrelated to the uniformity of the optical aperture shape or light field control, and therefore Patent Document 1 does not disclose the problem of poor uniformity in the size or shape of the optical aperture of each VCSEL, nor does it disclose technical means such as a specific method and a combination of specific compounds for solving the problem of variations in the size or shape of the optical aperture of each VCSEL.

[0009] Furthermore, Patent Document 1 does not disclose any technical means for controlling the content of a specific element in a specific compound within a specific range. However, some embodiments of the present invention use this technical means to prevent the oxidation rate of each VCSEL from being too fast, and not only to match the size or shape of the optical aperture, but also to narrow the divergence angle of the VCSEL when only a single optical confinement layer is used.

[0010] Furthermore, Patent Document 1 does not disclose how to make the optical apertures of the two current confinement layers substantially the same size by a specific method and a specific combination of compounds, but this may also be a feasible solution. Specifically, the inventors of the present application have found that the optical apertures of the two optical confinement layers can actually be the same size when the two optical confinement layers are made of specific and / or the same compounds. If the optical apertures of the optical confinement layers are the same size, the size or shape of the optical apertures of the semiconductor epitaxial structure can be more consistent if the compound components and / or insulating process of the two optical confinement layers are set to exactly the same conditions. [Means for solving the problem]

[0011] Therefore, one embodiment of the present invention provides a semiconductor epitaxial structure including a substrate, a lower Bragg reflector (DBR) layer (hereinafter referred to as the "lower DBR layer"), an active region, an upper Bragg reflector (DBR) layer (hereinafter referred to as the "upper DBR layer"), and an optical confinement layer. The lower DBR layer is located on the substrate. The active region is located on the lower DBR layer and includes two active layers. The upper DBR layer is located on the active region. The optical confinement layer is located between the two active layers, and a material of the optical confinement layer includes a phosphorus (P)-containing compound. The optical confinement layer includes an insulating region and a non-insulating region, and the insulating region surrounds the non-insulating region.

[0012] In another embodiment of the present invention, there is provided a semiconductor epitaxial structure including a substrate, a lower DBR layer, an active region, an upper DBR layer, and an optical confinement layer. The lower DBR layer is located on the substrate. The active region is located on the lower DBR layer. The optical confinement layer is located outside the active region, and a material of the optical confinement layer includes a phosphorus (P)-containing compound. The optical confinement layer includes an insulating region and a non-insulating region, and the insulating region surrounds the non-insulating region. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing a semiconductor epitaxial structure according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic diagram showing a semiconductor epitaxial structure according to a second embodiment of the present invention. [Diagram 3] FIG. 11 is a schematic diagram showing a semiconductor epitaxial structure according to a third embodiment of the present invention. [Figure 4] FIG. 11 is a schematic diagram showing a semiconductor epitaxial structure according to a fourth embodiment of the present invention. [Diagram 5] FIG. 11 is a schematic diagram showing a semiconductor epitaxial structure according to a fifth embodiment of the present invention. [Figure 6]FIG. 13 is a schematic diagram showing a semiconductor epitaxial structure according to a sixth embodiment of the present invention. [Figure 7] FIG. 2 is a diagram showing the oxidation rates of the optical confinement layer (containing an AlAs1-xPx compound) of FIG. 1 and a conventional current confinement layer (containing an AlAs compound). [Figure 8] FIG. 2 is a diagram showing the far-field distribution of the conventional structure (wherein the current confinement layer contains an AlGaAs compound) based on the semiconductor epitaxial structure shown in FIG. [Figure 9A] FIG. 2 is a far-field distribution of the semiconductor epitaxial structure shown in FIG. 1, in which the optical confinement layer contains an AlAs1-xPx compound, where x is 0.02. [Figure 9B] FIG. 2 is a far-field distribution of the semiconductor epitaxial structure shown in FIG. 1, in which the optical confinement layer contains an AlAs1-xPx compound, where x is 0.04. [Figure 9C] FIG. 2 shows the far-field distribution of the semiconductor epitaxial structure shown in FIG. 1 (the optical confinement layer contains an AlAs1-xPx compound, where x is 0.06). [Figure 9D] FIG. 2 shows the far-field distribution of the semiconductor epitaxial structure shown in FIG. 1 (the optical confinement layer contains an AlAs1-xPx compound, where x is 0.08). [Figure 9E] FIG. 2 shows the far-field distribution of the semiconductor epitaxial structure shown in FIG. 1 (the optical confinement layer contains an AlAs1-xPx compound, where x is 0.10). [Figure 9F] FIG. 2 shows the far-field distribution of the semiconductor epitaxial structure shown in FIG. 1 (the optical confinement layer contains an AlAs1-xPx compound, where x is 0.12). [Figure 10] FIG. 2 is a diagram showing the far-field distribution of the conventional structure (wherein the current confinement layer contains an AlAs compound) based on the semiconductor epitaxial structure shown in FIG. [Figure 11] FIG. 5 is a diagram showing the far-field distribution of a conventional structure (wherein the current confinement layer contains an AlGaAs compound (for example, an Al1-yGayAs compound, where y is 0.02)) according to the semiconductor epitaxial structure shown in FIG. [Figure 12]FIG. 5 is a diagram showing the far-field distribution of the semiconductor epitaxial structure shown in FIG. 4 (the optical confinement layers uniformly contain AlAs1-xPx compounds, where x is 0.04). [Figure 13] FIG. 7 is a diagram showing the far-field distribution of a conventional structure (wherein the current confinement layer contains an AlGaAs compound (for example, an Al1-yGayAs compound, where y is 0.02)) according to the semiconductor epitaxial structure shown in FIG. 6. [Figure 14] FIG. 7 is a diagram showing the far-field distribution of the semiconductor epitaxial structure shown in FIG. 6 (the optical confinement layer uniformly contains AlAs1-xPx compounds, where x is 0.04). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the embodiments of the present invention will be described in more detail with reference to the drawings and reference numerals so that those skilled in the art can practice the present invention after reading the specification.

[0015] Also, spatial terms such as "below," "beneath," "lower," "below," "lower," "above," "above," "on," "higher," "within," "inside," "outside," "outside of," and the like are used herein to facilitate the description of the relationship of one or more elements or features shown in the drawings to one or more other elements or features. Spatial terms are intended to encompass alternative orientations of the device during use or operation in addition to the orientation depicted in the drawings.

[0016] The present specification provides different examples to illustrate the technical features of different embodiments. For example, a reference to "some embodiments" throughout this specification means that a particular feature, structure, or characteristic described in an embodiment is included in at least one embodiment. Thus, the phrase "in some embodiments" appearing in different places throughout this specification does not necessarily refer to the same embodiment. However, a particular feature, structure, or characteristic may be implemented in one or more embodiments in any suitable manner.

[0017] Additionally, as used herein, the terms "comprise," "include," "have," "wherein," or variations thereof include corresponding features in a similar manner to the term "comprise." Additionally, a "layer" may be a single layer or multiple layers, and a "portion" of an epitaxial layer may be one layer of the epitaxial layer or multiple adjacent layers.

[0018] In addition, so-called ternary compounds may contain other elements other than the three elements in trace amounts in addition to the three elements. For example, when an AlAsP semiconductor layer is adjacent to an AlGaAs semiconductor layer, a trace element of Ga often appears in the AlAsP semiconductor layer in the analysis result of a secondary ion mass spectrometer (SIMS). Similarly, when an adjacent layer of the AlAsP semiconductor layer contains other elements such as In and Sb, the analysis result of SIMS may show that the AlAsP semiconductor layer also contains elements such as In and Sb. In addition, the AlAsP semiconductor layer is not only influenced by the adjacent semiconductor layer, but also the phosphorus (P) content of the AlAsP semiconductor layer may be significantly different from the actual phosphorus content due to the quantitative analysis of SIMS (its own measurement error) if the AlAsP semiconductor layer is thin, for example, the phosphorus content may be less than the actual phosphorus content.

[0019] To simplify the drawings, most of the drawings only show the active layer, the tunnel junction layer, the optical confinement layer, etc., and do not specifically show or draw the epitaxial layers such as the spacer layer, the ohmic contact layer, etc., even though these epitaxial layers are necessary or preferred structures for the VCSEL. The spacer layer is generally formed above and / or below the active layer, the optical confinement layer, the tunnel junction layer, or other epitaxial layers. The spacer layer can be selectively provided according to actual needs, and the material, composition, thickness, doping, and doping concentration of each spacer layer can also be appropriately adjusted according to actual needs.

[0020] Referring to FIG. 1 and FIG. 2, FIG. 1 and FIG. 2 are schematic diagrams showing semiconductor epitaxial structures 100a and 100b according to the first and second embodiments of the present invention, respectively. In FIG. 1 and FIG. 2, the semiconductor epitaxial structure 100a includes a substrate 10, a lower DBR layer 12, an active region A, an upper DBR layer 14, and an optical confinement layer 16 (the first optical confinement layer 161 shown in FIG. 1 or FIG. 2). It should be mentioned that in different embodiments, the optical confinement layer 16 can be, but is not limited to, a single-layer optical confinement layer or a multi-layer optical confinement layer. For convenience of explanation, different embodiments will be described with corresponding symbols. For example, FIG. 1 and FIG. 2 show an embodiment of a single-layer optical confinement layer, that is, the optical confinement layer will be described by taking the first optical confinement layer 161 as an example. FIG. 4 illustrates an embodiment of a multi-layer optical confinement layer, namely, a first optical confinement layer 161 and a second optical confinement layer 164 are taken as examples to illustrate the optical confinement layers and another optical confinement layer (described in detail below), all of which can be understood by those skilled in the art.

[0021] In FIG. 1 and FIG. 2, the lower DBR layer 12 is located on the substrate 10. The lower DBR layer 12 may be in direct contact with the substrate 10, or may be indirectly located on the substrate 10 via, for example, a semiconductor layer or a spacer layer. The active region A is located on the lower DBR layer 12. The active region A may be in direct contact with the lower DBR layer 12, or may be indirectly located on the lower DBR layer 12 via, for example, a semiconductor layer or a spacer layer. The active region A may include a single active layer (the first active layer a1 shown in FIG. 1) or multiple active layers (the first active layer a1 and the second active layer a2 shown in FIG. 4, which will be described in detail later). The upper DBR layer 14 is located on the active region A. The materials and specifications of the substrate 10, the lower DBR layer 12, the active layer of the active region A (for example, the first active layer a1 and the second active layer a2 shown in FIG. 3, which will be described in detail later), and the upper DBR layer 14 may be generally used or well known in the technical field to which they belong, and are not particularly limited. For example, the substrate 10 may be a gallium arsenide (GaAs) substrate or a germanium (Ge) substrate.

[0022] The semiconductor epitaxial structure 100a has two opposing side surfaces spaced apart from each other, and one of the two opposing side surfaces is a light emitting surface, for example, a first light emitting surface S1 or a second light emitting surface S2 shown in FIG. 1, where the first light emitting surface S1 is the side of the semiconductor epitaxial structure 100a away from the substrate 10, and the second light emitting surface S2 is the side of the semiconductor epitaxial structure 100a closer to the substrate 10. The light emitting surface is essentially parallel to the epitaxial plane or the substrate 10 plane. In some embodiments, according to the direction of laser light emission, the semiconductor epitaxial structure 100a can be classified as a front-side emission type or a back-side emission type. When the total reflectance of the upper DBR layer 14 is smaller than the total reflectance of the lower DBR layer 12, the VCSEL constructed from the semiconductor epitaxial structure 100a is called a front-side emission type VCSEL. When the total reflectivity of the upper DBR layers 14 is greater than the total reflectivity of the lower DBR layers 12, the VCSEL constructed from the semiconductor epitaxial structure 100a is called a back-emitting VCSEL.

[0023] In some embodiments, the optical confinement layer 16 is located between the active region A and the light output surface. For example, in FIG. 1, the first optical confinement layer 161 is located between the active region A and the first light output surface S1, and for example, in FIG. 1, the first optical confinement layer 161 is located below the upper DBR layer 14 (for example, between the upper DBR layer 14 and the active region A). Or, for example, in FIG. 2, the first optical confinement layer 161 is located between the active region A and the second light output surface S2, and for example, in FIG. 2, the first optical confinement layer 161 is located above the lower DBR layer 12 (for example, between the lower DBR layer 12 and the active region A). The optical confinement layer 16 (for example, the first optical confinement layer 161, the second optical confinement layer 164, or both) includes a phosphorus (P)-containing compound. Preferably, the phosphorus-containing compound is a ternary compound or a quaternary compound, and the ternary compound or the quaternary compound contains at least phosphorus (P) element to facilitate subsequent insulation treatment of a part of the optical confinement layer 16. For example, the ternary compound is an AlAsP compound or an AlAsP compound-containing compound, and the quaternary compound is an AlGaAsP compound. Thus, after insulation treatment is performed on a part of the optical confinement layer 16, the optical confinement layer 16 (e.g., the first optical confinement layer 161) may have an insulating region (e.g., the first insulating region 162) that is insulated and a non-insulating region (e.g., the first non-insulating region 163) that is not insulated. The insulation treatment may be, for example, an appropriate insulating treatment method such as an oxidation treatment, an ion implantation treatment, or an etching process (but is not limited to these). It should be understood that the insulating region described herein (e.g., the first insulating region 162 shown in FIG. 1) is a region in the optical confinement layer 16 (e.g., the first optical confinement layer 161) having a high resistance (clearly higher than the resistance of the non-insulating region (e.g., the first non-insulating region 163)). Since the resistance of the non-insulating region (eg, the first non-insulating region 163) is low, the non-insulating region can be used as an optical aperture (OA).

[0024] In some embodiments, the optical confinement layer 16 includes an AlAsP compound (or an AlGaAsP compound). In these embodiments, the optical confinement layer 16 (for example, the first optical confinement layer 161 shown in FIG. 1) includes an AlAsP compound (or an AlGaAsP compound), which is more stable (the oxidation rate of AlAsP (or AlGaAsP) is slower than that of AlAs) and easier to control during the fabrication process of the optical confinement layer 16, and therefore the area or shape of the optical aperture of each VCSEL is more consistent. In particular, when the optical confinement layer 16 (for example, the first optical confinement layer 161) includes an AlAsP compound (or an AlGaAsP compound) and a single-layer optical confinement layer 16 is disposed between the active region A and the light emission surface (for example, the first light emission surface S1 or the second light emission surface S2), the single-layer optical confinement layer 16 (for example, the first optical confinement layer 161) alone can provide the VCSEL with a small divergence angle. The active region A is not limited to including one or more active layers (e.g., the first active layer a1 and the second active layer a2, which will be described in detail later). Preferably, when the phosphorus content of the AlAsP compound (or the AlGaAsP compound) is in a suitable range, the fabrication process of the optical confinement layer 16 is more stable or controllable, the divergence angle can be smaller, and the stress of the VCSEL can be reduced. Therefore, in the case of multiple optical confinement layers (e.g., the first optical confinement layer 161 and the second optical confinement layer 164 in FIG. 4, which will be described in detail later), the shape similarity between each optical aperture in the same VCSEL (e.g., the first non-insulating region 163 and the second non-insulating region 166 in FIG. 4) can be higher. In addition, the shape similarity between each optical aperture of the VCSEL can also be higher. At the same time, a semiconductor epitaxial structure including multiple optical confinement layers (e.g., the semiconductor epitaxial structure 100d in FIG. 4, which will be described in detail later) can also have a smaller divergence angle than.

[0025] As described above, compared to the divergence angle of a conventional VCSEL or a VCSEL including a current confinement layer made of other materials (e.g., greater than 20 degrees), the semiconductor epitaxial structures of some embodiments of the present invention (e.g., semiconductor epitaxial structures 100a, 100b in FIGS. 1 and 2) may have a smaller divergence angle (e.g., 13.297 degrees, detailed in Table 1 and Table 2 below). Since the semiconductor epitaxial structures (e.g., 100a, 100b) have a smaller divergence angle, broader applications are possible.

[0026] In some embodiments with a controllable or stable oxidation rate, the molar percentage of the phosphorus component of the phosphorus-containing compound is greater than 0% and less than or equal to 30%, or greater than 0% and less than or equal to 20%, or greater than 0% and less than or equal to 15%. For example, in some embodiments, the optical confinement layer 16 (e.g., the first optical confinement layer 161) contains an AlAsP compound, and the AlAsP compound is, for example, AlAs 1-x P x which can be represented as, with the molar ratio of As to P being (1 - x):x, for example, 0 < x ≤ 0.3 (or 0 < x ≤ 0.20, or 0 < x ≤ 0.15, or 0 < x ≤ 0.12, or 0 < x ≤ 0.10, or 0 < x ≤ 0.10, 0 < x ≤ 0.08 or 0 < x ≤ 0.06). Within the above range, not only is the oxidation rate of AlAs 1-x P x close to that of AlGaAs, but also the divergence angle of AlAs 1-x P x becomes smaller and the stress does not become too large. For example, the first optical confinement layer 161 in FIG. 1 (or, for example, the second optical confinement layer 164 in FIG. 4) is AlAs 1-x P xThe compound includes an AlAs, wherein x is about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or any other value greater than 0 or less than or equal to 0.3. If x is not within the above range (e.g., if it is (significantly) greater than 0.3), then the AlAs 1-x P x This indicates that the content of phosphorus element contained in the compound is not within the content range that can produce a significant effect.

[0027] In some embodiments, the optical confinement layer 16 (e.g., the first optical confinement layer 161) does not include an aluminum gallium arsenide (AlGaAs) compound. The inventors have found that when an AlGaAs compound is included in the optical confinement layer (e.g., 16), the semiconductor epitaxial structure (e.g., 100a or 100b) has a larger divergence angle than the optical confinement layer 16. In other words, when the semiconductor epitaxial structure includes an optical confinement layer containing the AlGaAs compound, the objective of the invention, which is to provide a small divergence angle according to some embodiments of the invention, cannot be achieved.

[0028] As can be seen from the above, in some embodiments, the optical confinement layer 16 of the semiconductor epitaxial structures 100a, 100b including a single optical confinement layer (e.g., the first optical confinement layer 161) and a single active layer (e.g., the first active layer a1) as shown in, for example, FIGS. 1 and 2 can have a more stable and easily controllable oxidation rate, and the resulting semiconductor epitaxial structure (e.g., 100a or 100b) can also provide a smaller divergence angle.

[0029] In some embodiments, the optical confinement layer 16 (for example, the second optical confinement layer 164 shown in FIG. 3) is located in the active region A. Referring to FIG. 3, FIG. 3 is a schematic diagram showing a semiconductor epitaxial structure 100c according to a third embodiment of the present invention. The difference from the optical confinement layer 16 (i.e., the first optical confinement layer 161) shown in FIG. 1 and FIG. 2 is that the active region A in FIG. 3 includes at least two active layers (for example, the first active layer a1 and the second active layer a2). The optical confinement layer 16 (i.e., the second optical confinement layer 164) shown in FIG. 3 is located in the active region A and is disposed between at least two active layers a1 and a2. Note that in FIG. 3, the active region A further includes at least one tunnel junction layer 17, and the tunnel junction layer 17 (for example, the first tunnel junction layer 170) is disposed between the two active layers a1 and a2. The number of the tunnel junction layers 17 can be increased according to the number of the active layers a1 and a2. The second optical confinement layer 164 is located, for example, between the second active layer a2 and the tunnel junction layer 17 (for example, the first tunnel junction layer 170). By providing the tunnel junction layer 17 (which must operate under reverse bias) between the two active layers a1 and a2, carriers are injected into the next active layer by the tunnel effect (also called carrier recycling) of the tunnel junction layer 17. The second optical confinement layer 164 may also include a second insulating region 165 and a second non-insulating region 166. A specific embodiment can be referred to the embodiment of the optical confinement layer 16 (including the first optical confinement layer 161, the first insulating region 162, and the first non-insulating region 163) described above, and a detailed description thereof will be omitted here.

[0030] As can be seen from the above, in some embodiments, for example, the optical confinement layer 16 of the semiconductor epitaxial structure 100c including a single optical confinement layer (e.g., the second optical confinement layer 164) and multiple active layers (e.g., the first active layer a1 and the second active layer a2) shown in FIG. 3 can also have a more stable and easily controllable oxidation rate, and the resulting semiconductor epitaxial structure 100c can provide a smaller divergence angle than the optical confinement layer 16 of the semiconductor epitaxial structure 100c shown in FIG.

[0031] In some embodiments, the semiconductor epitaxial structure (e.g., the semiconductor epitaxial structure 100d in FIG. 4) may further include another optical confinement layer, and the semiconductor epitaxial structure may include at least two optical confinement layers. At least one optical confinement layer (e.g., the first optical confinement layer 161 in FIG. 4) in the at least two optical confinement layers is located outside the active region A (e.g., between the first light emission surface S1 and the active region A), and another at least one optical confinement layer (e.g., the second optical confinement layer 164 in FIG. 4) in the at least two optical confinement layers is located inside the active region A (e.g., between the first tunnel junction layer 170 and the second active layer a2).

[0032] 4 and 5, which are schematic diagrams showing semiconductor epitaxial structures 100d and 100e according to the fourth and fifth embodiments of the present invention. The difference between the semiconductor epitaxial structures 100a, 100b, and 100c shown in FIGS. 1, 2, and 3 is that the optical confinement layer 16 of the semiconductor epitaxial structures 100d and 100e shown in FIGS. 4 and 5 includes a first optical confinement layer 161 and a second optical confinement layer 164. The first optical confinement layer 161 is located outside the active region A, for example, between the active region A and the optical emission surface (for example, the first optical emission surface S1 or the second optical emission surface S2). In FIG. 4, the first optical confinement layer 161 is located below the upper DBR layer 14 (for example, between the upper DBR layer 14 and the active region A). 5, the first optical confinement layer 161 is located on the lower DBR layer 12 (e.g., between the lower DBR layer 12 and the active region A). The second optical confinement layer 164 is located inside the active region A, for example, between two active layers a1 and a2. For specific embodiments of the first optical confinement layer 161 located outside the active region A and the second optical confinement layer 164 located inside the active region A, reference may be made to the above-mentioned embodiments related to the first optical confinement layer 161 and the second optical confinement layer 164, and detailed descriptions thereof will be omitted here.

[0033] In some embodiments, the material specifications of the at least two light confinement layers (e.g., the first light confinement layer 161 and the second light confinement layer 164 in FIG. 4) are substantially the same material specifications. For example, the materials of the at least two light confinement layers are both AlAsP compounds (or AlGaAsP compounds) with substantially the same components and mixing ratios, such as AlAs 1-x P x represented by, where 0 < x ≤ 0.3 (or 0 < x ≤ 0.20, 0 < x ≤ 0.15, or 0 < x ≤ 0.12, or 0 < x ≤ 0.10, or 0 < x ≤ 0.10, 0 < x ≤ 0.08 or 0 < x ≤ 0.06). Specific embodiments of the material of the light confinement layer 16 can refer to the embodiments regarding the materials of the aforementioned first light confinement layer 161 and second light confinement layer 164, and the detailed description thereof is omitted here.

[0034] In some embodiments, the first non-insulating region 163 and the second non-insulating region 166 are each substantially circular and form concentric circles on the projection plane (e.g., the XY plane in FIG. 4 or FIG. 5).

[0035] In some embodiments, the first non-insulating region 163 and the second non-insulating region 166 are each substantially circular, and the average diameter d of the first non-insulating region 163 and the average diameter d' of the second non-insulating region 166 may be the same or different. In some embodiments, the area of the first non-insulating region 163 and the area of the second non-insulating region 166 may be the same or different. In some embodiments, the area of the first non-insulating region 163 may be smaller than, equal to, or larger than the area of the second non-insulating region 166. In some embodiments, the materials of the at least two light confinement layers (e.g., the first light confinement layer 161 and the second light confinement layer 164 in FIG. 4) each contain a compound containing an AlAsP compound (or AlGaAsP compound), and the areas of the non-insulating regions of the at least two light confinement layers may be the same or different.

[0036] As can be seen from the above, in some embodiments, the multiple optical confinement layers of the semiconductor epitaxial structures 100d, 100e including multiple optical confinement layers (e.g., the first optical confinement layer 161 and the second optical confinement layer 164) and multiple active layers (e.g., the first active layer a1 and the second active layer a2) shown in, for example, FIGS. 4 and 5 can have a more stable and easily controllable oxidation rate, so that even if the multiple optical confinement layers and the multiple active layers are combined, the resulting semiconductor epitaxial structures 100d, 100e can still provide a smaller divergence angle than

[0037] The above-mentioned technical effects will be further described below through experimental examples. In Experimental Examples 1 to 4, the AlAs 1-x P x The insulation treatment for both the optical confinement layer containing a compound and the conventional current confinement layer is an oxidation treatment.

[0038] (Experimental Example 1: Comparison of divergence angles - Semiconductor epitaxial structure including a single-layer active layer and a single-layer optical confinement layer (compared to a conventional semiconductor epitaxial structure including an AlGaAs current confinement layer) 1, 8, and 9A to 9F, FIG. 8 shows the far field profile of the conventional structure (wherein the current confinement layer contains an AlGaAs compound) based on the semiconductor epitaxial structure 100a shown in FIG. 1. FIGS. 9A to 9F show the far field profile of the conventional structure (wherein the current confinement layer contains an AlGaAs compound) based on the semiconductor epitaxial structure 100a shown in FIG. 1. 1-x P x The far-field distributions of the current confinement layer shown in FIG. 8 and the average diameter d (FIG. 1) of the first non-insulating region 163 shown in FIG. 9A to FIG. 9F are both about 8 μm, and these far-field distributions were obtained by measuring under a continuous wave (CW) bias current of 10 mA. According to the far-field distributions shown in FIG. 8 and FIG. 9A to FIG. 9F, the divergence angles corresponding to the 1 / e2 widths of each semiconductor epitaxial structure are summarized in Table 1.

[0039] [Table 1]

[0040] As can be seen from Table 1, FIG. 8, and FIG. 9A to FIG. 9F, in the case of a semiconductor epitaxial structure including a single active layer and a single optical confinement layer, an AlGaAs compound (e.g., Al 1-y Ga y The divergence angle of a conventional semiconductor epitaxial structure containing AlAs (a compound in which y is 0.02) is about 20.985 degrees, which is comparable to that of some embodiments of the present invention. 0.98 P 0.02 The compound (i.e., x is 0.02) is 0.96 P 0.04 The compound (i.e., x is 0.04) is 0.94 P 0.06 The compound (i.e., x is 0.06) is 0.92 P 0.08 The compound (i.e., x is 0.08) is 0.90 P 0.10 The compound (i.e., x is 0.10) is 0.88 P 0.12 The divergence angles of the six semiconductor epitaxial structures 100a containing the compound (i.e., x is 0.12) are about 13.297 degrees, 13.814 degrees, 14.728 degrees, 15.263 degrees, 17.744 degrees, and 18.770 degrees, respectively, and the divergence angles of the conventional AlGaAs compound (e.g., Al 1-y Ga y As can be seen from this, some embodiments of the present invention can be realized by using an AlGaAs compound (e.g., AlAsP compound or AlGaAsP compound) in the optical confinement layer 16 (e.g., the first optical confinement layer 161). 0.98 Ga 0.02 As a result, the divergence angle can be smaller than that of conventional ones containing arsenic compounds.

[0041] Based on this, compared to conventional semiconductor epitaxial structures (wherein the current confinement layer contains an AlGaAs compound), some embodiments of the present invention may include a single conductive layer (e.g., a1) and a single confinement layer (e.g., 161), but the resulting semiconductor epitaxial structure (e.g., 100a) may provide a smaller divergence angle than is possible with conventional semiconductor epitaxial structures (wherein the current confinement layer contains an AlGaAs compound).

[0042] (Experimental Example 2: Comparison of oxidation rate and divergence angle - Semiconductor epitaxial structure including a single-layer active layer and a single-layer optical confinement layer (compared to a semiconductor epitaxial structure including a conventional AlAs current confinement layer) Referring to FIG. 1 and FIG. 7, FIG. 7 shows the first optical confinement layer 161 (AlAs 1-x P x 1 shows the oxidation rates of a current confinement layer (containing an AlAs compound) and a conventional current confinement layer (containing an AlAs compound). As shown in FIG. 1, the semiconductor epitaxial structure 100a includes a single active layer (i.e., a first active layer a1) and a single optical confinement layer (i.e., a first optical confinement layer 161), which is located between the upper DBR layer 14 and the active region A. The first optical confinement layer 161 is made of AlAs 1-x P x The first optical confinement layer 161 includes a current confinement layer containing a conventional AlAs compound, and x is 0, 0.02, 0.04, 0.08, 0.10, and 0.12, respectively. Here, when x is 0, it indicates that the first optical confinement layer 161 includes a current confinement layer containing a conventional AlAs compound (i.e., x is 0.0). Next, the oxidation rate of the current confinement layer containing a conventional AlAs compound (i.e., x is 0.0) is taken as the standard oxidation rate (i.e., 100%, this oxidation rate is considered to be too fast), and the data of each oxidation rate is standardized and then summarized in Table 2 below. The obtained oxidation rate (standardized) indicates that the oxidation rate (standardized) corresponding to some embodiments of the present invention is lower than the oxidation rate of the current confinement layer containing a conventional AlAs compound (when x is 0.0) as long as it is lower than the standard oxidation rate (100%), and is slower than the oxidation rate of conventional AlAs.

[0043] [Table 2]

[0044] As can be seen from Table 2 and Figure 7 above, AlAs 1-x P x When x (i.e., phosphorus (P) content) is gradually increased to 0.02, 0.04, 0.08, 0.10 and 0.12, respectively, the obtained oxidation rates (normalized) are 89, 59, 37, 27 and 21, which shows a tendency that the oxidation rate gradually becomes slower and easier to control. 1-x P x It has been shown that the phosphorus content in the SiO2 positively affects the oxidation rate, and that, at least within the specified range of phosphorus content, some embodiments of the present invention can provide more stable and easily controllable oxidation rates.

[0045] Next, referring to Fig. 1, Fig. 9A to Fig. 9F, and Fig. 10, Fig. 10 shows the far-field distribution of the conventional structure (wherein the current confinement layer contains an AlAs compound) according to the semiconductor epitaxial structure 100a shown in Fig. 1. Similar to the average diameter d (Fig. 1) of the first non-insulating region 163 in Figs. 9A to 9F, the diameter of the optical aperture of the current confinement layer in Fig. 10 is also about 8 μm, and the far-field distribution was obtained by measuring with a continuous wave bias current of 10 mA. According to the far-field distributions shown in Figs. 9A to 9F and Fig. 10, the 1 / e 2 The divergence angles corresponding to each width are shown in Table 2 above.

[0046] As can be seen from Table 2 above, FIGS. 9A to 9F, and FIG. 10, in the case of a semiconductor epitaxial structure including a single active layer and a single optical confinement layer, the divergence angle of a conventional semiconductor epitaxial structure containing an AlAs compound is about 14.380 degrees. Compared with some embodiments of the present invention, the divergence angle of the AlAs 0.98 P 0.02 The compound (i.e., x is 0.02) is 0.96 P 0.04 The compound (i.e., x is 0.04) is 0.94 P 0.06 The compound (i.e., x is 0.06) is 0.92 P 0.08The compound (i.e., x is 0.08) is 0.90 P 0.10 The compound (i.e., x is 0.10) is 0.88 P 0.12 The divergence angles of six types of semiconductor epitaxial structures 100a containing the compound (i.e., x is 0.12) were approximately 13.297 degrees, 13.814 degrees, 14.728 degrees, 15.263 degrees, 17.744 degrees, and 18.770 degrees, respectively. As can be seen from this, some embodiments of the present invention can have a small divergence angle similar to that of a conventional structure containing an AlAs compound by containing a specific AlAsP compound (or an AlGaAsP compound) in the optical confinement layer 16 (e.g., the first optical confinement layer 161).

[0047] Based on this, compared to conventional semiconductor epitaxial structures (wherein the current confinement layer contains an AlAs compound), some embodiments of the present invention may include a single active layer (e.g., a1) and a single confinement layer (e.g., 161), but the resulting semiconductor epitaxial structure (e.g., 100a) may provide a smaller divergence angle than is possible with conventional semiconductor epitaxial structures (wherein the current confinement layer contains an AlAs compound).

[0048] (Experimental Example 3: Divergence angle of a semiconductor epitaxial structure including a multi-layer active layer and a single-layer optical confinement layer (compared to a conventional current confinement layer including AlGaAs)) 4, 11 and 12, FIG. 11 shows a conventional structure using the semiconductor epitaxial structure 100d shown in FIG. 4 (the current confinement layer is made of an AlGaAs compound (e.g., Al 1-y Ga y FIG. 12 shows the far-field distribution of the semiconductor epitaxial structure 100d shown in FIG. 4 (both optical confinement layers are AlAs, 1-x P x11 shows the far-field distribution of a semiconductor epitaxial structure (containing a compound, x being 0.04). The diameter of the optical aperture of the current confinement layer in FIG. 11, the average diameter d of the first non-insulating region 163 (FIG. 4) and the average diameter d' of the second non-insulating region 166 (FIG. 4) in FIG. 12 are all about 10 μm, and these far-field distributions were obtained by measuring with a continuous wave bias current of 7 mA. According to the far-field distributions shown in FIGS. 11 and 12, the 1 / e 2 The divergence angles corresponding to each width are summarized in Table 3 below.

[0049] [Table 3]

[0050] As can be seen from Table 3 and FIGS. 11 and 12, in the case of a semiconductor epitaxial structure including a multi-layer active layer and a multi-layer optical confinement layer (two optical confinement layers), an AlGaAs compound (e.g., Al 1-y Ga y The divergence angle of a conventional semiconductor epitaxial structure containing AlAs (where y is 0.02) is about 26.257 degrees, compared to some embodiments of the present invention, which is about 1.088 degrees. 0.96 P 0.04 The divergence angle of the semiconductor epitaxial structure 100d containing the compound (i.e., x is 0.04) is about 14.786 degrees, and the divergence angle of the semiconductor epitaxial structure 100c containing the AlGaAs compound (e.g., Al 1-y Ga y As a result, the divergence angle is clearly smaller than that of a conventional semiconductor epitaxial structure containing a specific AlAsP compound (or an AlGaAsP compound) in the optical confinement layer 16 (e.g., the first optical confinement layer 161 and the second optical confinement layer 164), and thus, in some embodiments of the present invention, the optical confinement layer 16 contains a specific AlAsP compound (or an AlGaAsP compound), and thus, the optical confinement layer 16 can be formed from an AlGaAs compound (e.g., Al 0.98 Ga 0.02 The divergence angle can be clearly smaller than that of a conventional one containing a fluorine-containing compound (As).

[0051] Based on this, compared to conventional semiconductor epitaxial structures (wherein the current confinement layer contains an AlGaAs compound), some embodiments of the present invention may include multiple conductive layers (e.g., a1, a2) and multiple confinement layers (e.g., 161, 164), but the resulting semiconductor epitaxial structure (e.g., 100d) may provide a smaller divergence angle than is possible with conventional semiconductor epitaxial structures (wherein the current confinement layer contains an AlGaAs compound).

[0052] (Experimental Example 4: Comparison of divergence angles ─ Semiconductor epitaxial structure including multiple active layers and multiple optical confinement layers (six optical confinement layers) (conventional semiconductor epitaxial structure of current confinement layer containing AlGaAs)) Referring to Fig. 6, Fig. 6 is a schematic diagram showing a semiconductor epitaxial structure 100f according to a sixth embodiment of the present invention. In Fig. 6, the semiconductor epitaxial structure 100f includes six active layers and six optical confinement layers, of which five optical confinement layers (i.e., the second optical confinement layer 164, the third optical confinement layer 167, the fourth optical confinement layer 168, the fifth optical confinement layer 169, and the sixth optical confinement layer 160) are located within the active region A and are located between any two active layers, respectively, and the remaining one optical confinement layer (i.e., the first optical confinement layer 161) is located between the upper DBR layer 14 and the active region A. After each optical confinement layer 160, 161, 164, 167, 168, 169 is subjected to an oxidation treatment, each optical confinement layer 160, 161, 164, 167, 168, 169 forms a corresponding insulating region and a non-insulating region, and the specific embodiment can be referred to above, and the detailed description thereof will be omitted here. In some embodiments, the semiconductor epitaxial structure 100f includes a multi-layer tunnel junction layer 17 (e.g., including a first tunnel junction layer 170, a second tunnel junction layer 171, a third tunnel junction layer 172, a fourth tunnel junction layer 173, and a fifth tunnel junction layer 174), and each tunnel junction layer 170 to 174 can be located between any two active layers a1 to a6. In addition, the embodiments of each optical confinement layer 160, 161, 164, 167, 168, 169, each tunnel junction layer 170 to 174, and the remaining components may refer to the embodiments of each optical confinement layer 16, tunnel junction layer 17, and the remaining components described above, and detailed descriptions thereof will be omitted here.

[0053] 6, 13, and 14, FIG. 13 shows a conventional structure using the semiconductor epitaxial structure 100f shown in FIG. 6 (the current confinement layer is made of an AlGaAs compound (e.g., Al 1-y Ga y 14 shows the far-field distribution of the semiconductor epitaxial structure 100f shown in FIG. 6 (optical confinement layers 160, 161, 164, 167, 168, and 169 are all AlAs). 1-x P xThe far-field distributions of the current confinement layer in FIG. 13 and the average diameters d and d' (FIG. 6) of each non-insulating region (e.g., 163 and 166) in FIG. 14 are both about 20 μm, and these far-field distributions were obtained by measuring with a continuous wave bias current of 7 mA. According to the far-field distributions shown in FIG. 13 and FIG. 14, the 1 / e 2 The divergence angles corresponding to each width are summarized in Table 4 below.

[0054] [Table 4]

[0055] As can be seen from Table 4, in the case of a semiconductor epitaxial structure including multiple active layers and multiple optical confinement layers (six optical confinement layers), the AlGaAs compound (e.g., Al 1-y Ga y The divergence angle of a conventional semiconductor epitaxial structure containing AlAs (where y is 0.02) is about 29.986 degrees, compared to some embodiments of the present invention. 0.96 P 0.04 The divergence angle of the semiconductor epitaxial structure 100f containing the compound (i.e., x is 0.04) is about 12.264 degrees, and the divergence angle of the semiconductor epitaxial structure 100f containing the AlGaAs compound (e.g., Al 1-y Ga y The divergence angle is clearly smaller than that of a conventional semiconductor epitaxial structure containing an AlAsP compound (y=0.02). For this reason, some embodiments of the present invention can be realized by using an AlGaAs compound (e.g., AlGaAsP compound) in the optical confinement layer 16 (e.g., optical confinement layers 160, 161, 164, 167, 168, 169). 0.98 Ga 0.02 The divergence angle can be clearly smaller than that of a conventional one containing a fluorine-containing compound (As).

[0056] Based on this, compared to conventional semiconductor epitaxial structures (wherein the current confinement layer contains an AlGaAs compound), some embodiments of the present invention include multiple conductive layers (e.g., a1 to a6) and multiple confinement layers (e.g., 160, 161, 164, 167, 168, 169), but the resulting semiconductor epitaxial structure (e.g., 100f) can provide a smaller divergence angle than expected.

[0057] In summary, in some embodiments of the present invention, the optical confinement layer is used to solve the technical problem that the insulation process (oxidation process, etc.) rate of the conventional current confinement layer is unstable and difficult to control, and the semiconductor epitaxial structure (e.g., VCSEL) including the optical confinement layer has the advantage and characteristic of a smaller divergence angle than, which is useful for a wide range of scientific and technological applications. In another embodiment of the present invention, the optical confinement layer containing a specific component (e.g., AlAsP compound (or AlGaAsP compound)) is used to solve the technical problem that the insulation process (oxidation process, etc.) rate of the conventional current confinement layer is unstable and difficult to control, and the semiconductor epitaxial structure (e.g., VCSEL) including the optical confinement layer has the advantage and characteristic of a smaller divergence angle than, which is useful for a wide range of scientific and technological applications. In addition, by combining the above advantages and characteristics, in some embodiments of the present invention, whether the semiconductor epitaxial structure includes a single optical confinement layer or multiple optical confinement layers, it can be manufactured by a more optimized manufacturing method, and the manufactured semiconductor epitaxial structure (e.g., VCSEL) also has the advantage and characteristic of a smaller divergence angle than.

[0058] Although the present invention discloses preferred embodiments as described above, these are by no means intended to limit the present invention, and any person familiar with the art may make various modifications and adaptations within the scope of the spirit and scope of the present invention. Therefore, the scope of protection of the present invention is based on the content defined in the claims attached hereto. [Explanation of symbols]

[0059] 100a, 100b, 100c, 100d, 100e, 100f Semiconductor epitaxial structure 10 Substrate 12 Lower DBR layer 14 Upper DBR layer 16 Optical confinement layer 160 6th optical confinement layer 161 First optical confinement layer 162 First Insulation Area 163 First non-insulated area 164 Second optical confinement layer 165 Second Insulation Area 166 Second non-insulated area 167 Third optical confinement layer 168 4th optical confinement layer 169 5th optical confinement layer 17 Tunnel junction layer 170 First tunnel junction layer 171 Second tunnel junction layer 172 Third tunnel junction layer 173 Fourth tunnel junction layer 174 5th tunnel junction layer A active area S1 1st light exit surface S2 Second light exit surface X coordinate X axis Y-axis of the coordinate Z coordinate Z axis a1 1st active layer a2 2nd active layer a3,a4,a5,a6 active layer d,d' average diameter

Claims

1. A substrate; a lower DBR layer located on the substrate; an active region located on the lower DBR layer and including two active layers; an upper DBR layer located on the active region; A semiconductor epitaxial structure, comprising: an AlAsP compound or an AlGaAsP compound; a molar percentage of a phosphorus (P) component in the AlAsP compound or the AlGaAsP compound is greater than 0% and less than or equal to 30%; and an insulating region and a non-insulating region, the insulating region including an optical confinement layer surrounding the non-insulating region.

2. 2. The semiconductor epitaxial structure of claim 1, wherein the mole percentage of the phosphorus component in the AlAsP compound or the AlGaAsP compound is greater than 0% and less than or equal to 20%.

3. 2. The semiconductor epitaxial structure of claim 1, wherein the mole percentage of the phosphorus component of the AlAsP compound or the AlGaAsP compound is greater than 0% and less than or equal to 15%.

4. the active region includes a tunnel junction layer located between two of the active layers; The semiconductor epitaxial structure of claim 1 , wherein the optical confinement layer is located between one of the two active layers and the tunnel junction layer.

5. further comprising another optical confinement layer located outside the active region; 5. The semiconductor epitaxial structure of claim 4, wherein a material of the another optical confinement layer comprises the AlAsP compound or the AlGaAsP compound and comprises the insulating region and the non-insulating region, the insulating region of the another optical confinement layer surrounding the non-insulating region of the another optical confinement layer.

6. The semiconductor epitaxial structure of claim 5 , wherein the further optical confinement layer is located below the upper DBR layer or above the lower DBR layer.

7. 6. The semiconductor epitaxial structure of claim 5, wherein an area of ​​the non-insulating region of the optical confinement layer is the same as an area of ​​the non-insulating region of the another optical confinement layer.

8. The semiconductor epitaxial structure of claim 5 , wherein an area of ​​the non-insulating region of the optical confinement layer is different from an area of ​​the non-insulating region of the another optical confinement layer.

9. 2. The semiconductor epitaxial structure of claim 1, wherein the substrate is a GaAs substrate or a Ge substrate.

10. A substrate; a lower DBR layer located on the substrate; an active region located on the lower DBR layer; an upper DBR layer located on the active region; an optical confinement layer located outside an active layer, the material of which includes an AlAsP compound or an AlGaAsP compound, the AlAsP compound or the AlGaAsP compound having a molar percentage of a phosphorus component (P) greater than 0% and less than or equal to 30%, the optical confinement layer having an insulating region and a non-insulating region, the insulating region surrounding the non-insulating region.

11. 11. The semiconductor epitaxial structure of claim 10, wherein the mole percentage of the phosphorus component of the AlAsP compound or the AlGaAsP compound is greater than 0% and less than or equal to 20%.

12. 11. The semiconductor epitaxial structure of claim 10, wherein the mole percentage of the phosphorus component of the AlAsP compound or the AlGaAsP compound is greater than 0% and less than or equal to 15%.

13. The semiconductor epitaxial structure of claim 10 , wherein the optical confinement layer is located below the upper DBR layer or above the lower DBR layer.

14. The active region includes two of the active layers, further comprising another optical confinement layer located between the two active regions; 11. The semiconductor epitaxial structure of claim 10, wherein a material of the another optical confinement layer comprises the AlAsP compound or the AlGaAsP compound and comprises the insulating region and the non-insulating region, the insulating region of the another optical confinement layer surrounding the non-insulating region of the another optical confinement layer.

15. the active region includes a tunnel junction layer located between two of the active layers; 15. The semiconductor epitaxial structure of claim 14, wherein the another optical confinement layer is located between one of the two active layers and the tunnel junction layer.

16. 15. The semiconductor epitaxial structure of claim 14, wherein an area of ​​the non-insulating region of the optical confinement layer is the same as an area of ​​the non-insulating region of the another optical confinement layer.

17. 15. The semiconductor epitaxial structure of claim 14, wherein an area of ​​the non-insulating region of the optical confinement layer is different from an area of ​​the non-insulating region of the another optical confinement layer.

18. 11. The semiconductor epitaxial structure of claim 10, wherein the substrate is a GaAs substrate or a Ge substrate.

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