Vertical Cavity Surface Emitting Laser

Abstract

A vertical cavity surface emitting laser is disclosed. The vertical cavity surface emitting laser according to the present disclosure includes: a lower mirror; an upper mirror; an active layer, which is arranged between the lower mirror and the upper mirror; a hole-forming layer, which is arranged between the upper mirror and the active layer and has an oxide layer and a window layer surrounded by the oxide layer; an annular groove, which penetrates the upper mirror, the hole-forming layer and the active layer and defines an isolation area inside; and a plurality of oxide holes, which are arranged in the isolation area surrounded by the groove and penetrate the upper mirror and the hole-forming layer.

Description

Technical Field

[0001] The present disclosure relates to a high reliability vertical cavity surface emitting laser. Background Art

[0002] A vertical-cavity surface-emitting laser (VCSEL) is a laser that emits a laser beam in a vertical direction from a substrate surface.

[0003] A typical VCSEL includes an active layer arranged between mirrors. Electrons and holes injected through the mirrors generate light in the active layer, and laser light is generated and emitted through the resonance of the mirrors.

[0004] It is necessary to confine the current flowing vertically in the VCSEL to a small area, and for this purpose, methods using etching and oxidation have been used in the past. For example, a circular groove can be formed by etching the mirror layer and the active layer to form an isolated column, and an oxide layer can be formed using the groove to concentrate the current to a small area of ​​the aperture.

[0005] However, in the case of forming holes by oxidation using the grooves, various problems arise. First, oxidation proceeds from the grooves to the inside of the pillars, but if the diameter of the pillars is large, the oxidation time is long and it is difficult to finely control the oxidation process. In addition, if the size of the pillars is made small, the area of ​​the contact layer of the ohmic contact to the upper lens will also be reduced, thereby reducing the connection area between the pad electrode and the contact layer, which has an adverse effect on reliability.

[0006] In particular, when forming a plurality of emitter arrays, since a plurality of pillars surrounded by trenches need to be formed, a large area of ​​etching is required. In particular, since the connection portion between the pad and the emitter passes through the trench when forming the pad electrode, there is a risk of electrical disconnection, thereby reducing the process yield. In addition, since a large area of ​​trenches is formed near the emitter, the reliability of the emitter is also negatively affected due to surface defects. Summary of the invention

[0007] Embodiments of the present disclosure provide a VCSEL with high reliability.

[0008] In particular, embodiments of the present disclosure provide a VCSEL capable of preventing electrical disconnection due to a trench from occurring.

[0009] Further, the embodiments of the present disclosure provide a VCSEL capable of preventing the performance of an emitter from being degraded due to defects.

[0010] A vertical cavity surface emitting laser (VCSEL) according to an embodiment of the present disclosure includes: a lower mirror; an upper mirror; an active layer, which is arranged between the lower mirror and the upper mirror; a hole-forming layer, which is arranged between the upper mirror and the active layer and has an oxide layer and a window layer surrounded by the oxide layer; an annular groove, which passes through the upper mirror, the hole-forming layer and the active layer and defines an isolation area inside; and a plurality of oxide holes, which are arranged in the isolation area surrounded by the groove and pass through the upper mirror and the hole-forming layer.

[0011] The groove may pass through a portion of the thickness of the lower lens.

[0012] The vertical cavity surface emitting laser may further include: an ohmic contact layer arranged on the upper mirror, wherein the ohmic contact layer includes a circular portion in a circular ring shape and a plurality of protrusions protruding to the outside of the circular portion, and the oxidation holes are arranged between the protrusions.

[0013] The circular ring shape may be a partial ring shape with a portion cut off.

[0014] The ohmic contact layer may have a symmetrical structure, and the protrusions are spaced apart from each other at the same interval.

[0015] The oxidation pore may have an elliptical shape.

[0016] The oxidation pores may have a circular shape or a quadrilateral shape.

[0017] The vertical cavity surface emitting laser may further include: a surface protection layer covering the ohmic contact layer and the upper lens and an upper insulating layer arranged on the surface protection layer, wherein the groove and the oxidation hole penetrate the surface protection layer, and the upper insulating layer covers the groove and the oxidation hole.

[0018] The vertical cavity surface emitting laser may further include: a plurality of through holes penetrating the upper insulating layer and the surface protection layer to expose the ohmic contact layer, wherein the through holes are arranged to correspond to the protrusions.

[0019] The vertical cavity surface emitting laser may further include: a pad and a connection portion disposed on the upper insulating layer, the pad being disposed outside the trench, and the connection portion extending from the pad to be electrically connected to the ohmic contact layer through the through hole.

[0020] According to another embodiment of the present disclosure, a vertical cavity surface emitting laser with an emitter array is provided. The VCSEL includes: a lower mirror; an upper mirror; an active layer, which is arranged between the lower mirror and the upper mirror; a hole-forming layer, which is arranged between the upper mirror and the active layer and has an oxide layer and a window layer surrounded by the oxide layer; an annular groove, which passes through the upper mirror, the hole-forming layer and the active layer and defines an isolation area inside; and a plurality of oxide holes, which are arranged in the isolation area surrounded by the groove and pass through the upper mirror and the hole-forming layer, and the emitter array is arranged in the isolation area surrounded by the groove, wherein the plurality of oxide holes are arranged to correspond to the emitters in the emitter array.

[0021] The groove may be formed from the upper lens through a partial thickness of the lower lens.

[0022] The vertical cavity surface emitting laser may further include: an ohmic contact layer arranged on the upper mirror corresponding to each emitter, wherein each ohmic contact layer may include a circular portion in a circular ring shape and a plurality of protrusions protruding outward from the circular portion, and the oxidation holes may be arranged between the protrusions.

[0023] The circular ring shape of the ohmic contact layer may be a partial ring shape with a portion cut off.

[0024] The ohmic contact layer may have a symmetrical structure, and the protrusions may be spaced apart from each other at the same interval.

[0025] The vertical cavity surface emitting laser may further include: a surface protection layer covering the ohmic contact layer and the upper lens and an upper insulating layer arranged on the surface protection layer, wherein the groove and the oxidation hole may penetrate the surface protection layer, and the upper insulating layer may cover the groove and the oxidation hole.

[0026] The vertical cavity surface emitting laser may further include: a plurality of through holes penetrating the upper insulating layer and the surface protection layer to expose the ohmic contact layer, wherein the through holes may be arranged to correspond to the protrusions.

[0027] The vertical cavity surface emitting laser may further include: a pad and a connection portion disposed on the upper insulating layer, wherein the pad may be disposed outside the groove, and the connection portion extends from the pad and is electrically connected to the ohmic contact layer through the through hole.

[0028] The connection portion may have a mesa shape including circular opening portions corresponding to the respective emitters.

[0029] The oxidation pores may have an elliptical shape, a circular shape, or a quadrilateral shape.

[0030] According to the embodiments of the present disclosure, by arranging the oxide holes in the isolation region surrounded by the trench, the window layer can be finely formed, and the surface defects generated by forming the trench can be prevented from moving near the window layer, so that a highly reliable VCSEL can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic plan view of a VCSEL according to an embodiment of the present disclosure.

[0032] Figure 2A It is enlarged to show Figure 1 Schematic plan view of the emitter region.

[0033] Figure 2B is along Figure 2A A schematic cross-sectional view taken along the section line AA.

[0034] Figure 3A , Figure 3B , Figure 4A , Figure 4B , Figure 5A as well as Figure 5B Schematic plan view and cross-sectional view for explaining a method of manufacturing a VCSEL according to an embodiment of the present disclosure.

[0035] Figure 6 is a schematic plan view of a VCSEL according to yet another embodiment of the present disclosure.

[0036] Fig. 7A It is enlarged to show Figure 6 A schematic plan view of a portion of an emitter array.

[0037] Figure 7B is along Fig. 7A A cross-sectional view taken along the section line BB.

[0038] Figure 7C is along Fig. 7A Cross-sectional view taken along section line CC.

[0039] Figure 8 It is a schematic plan view for explaining a modification example of the ohmic contact layer.

[0040] Fig. 9A , Fig. 9B as well as Fig. 9C It is a schematic plan view for explaining various modification examples for forming oxidation holes in an oxide layer.

[0041] Preferred Embodiments

[0042] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The embodiments described below are provided as examples in order to fully convey the ideas of the present disclosure to those of ordinary skill in the technical field to which the present disclosure belongs. Therefore, the present disclosure is not limited to the embodiments described below, and may also be embodied in other forms. Furthermore, for the sake of convenience, in the accompanying drawings, the width, length, thickness, etc. of the constituent elements may be exaggerated. Furthermore, when a constituent element is recorded as being "on top" or "above" another constituent element, it includes not only the situation where each part is located "immediately above" or "immediately above" another part, but also the situation where other constituent elements exist between each constituent element and another constituent element. Throughout the entire specification, the same figure numerals represent the same constituent elements.

[0043] A vertical cavity surface emitting laser (VCSEL) according to one embodiment of the present disclosure includes: a lower mirror; an upper mirror; an active layer, which is arranged between the lower mirror and the upper mirror; a hole-forming layer, which is arranged between the upper mirror and the active layer and has an oxide layer and a window layer surrounded by the oxide layer; an annular groove, which passes through the upper mirror, the hole-forming layer and the active layer and defines an isolation area inside; and a plurality of oxide holes, which are arranged in the isolation area surrounded by the groove and pass through the upper mirror and the hole-forming layer.

[0044] By arranging the oxide holes in the isolation region surrounded by the trench, the window layer can be finely formed, and surface defects generated by forming the trench can be prevented from moving near the window layer, thereby providing a highly reliable VCSEL.

[0045] In one embodiment, the groove may penetrate a portion of the thickness of the lower mirror.

[0046] Furthermore, the VCSEL may further include: an ohmic contact layer disposed on the upper mirror, wherein the ohmic contact layer includes a circular portion in a circular ring shape and a plurality of protrusions protruding to the outside of the circular portion, and the oxidation holes may be disposed between the protrusions.

[0047] Since the ohmic contact layer includes the protrusions and the oxidation holes are arranged between the protrusions, the oxidation holes can be arranged at a narrower pitch, so that the size of the emitter can be reduced.

[0048] In one embodiment, the circular ring shape may be a partial ring shape with a portion cut off.

[0049] In another embodiment, the ohmic contact layer has a symmetrical structure, and the protrusions may be spaced apart from each other at the same interval.

[0050] In one embodiment, the oxidation hole may have an elliptical shape.

[0051] In another embodiment, the oxidation pores may have a circular or quadrilateral shape.

[0052] In addition, the VCSEL may further include: a surface protection layer covering the ohmic contact layer and the upper mirror and an upper insulating layer arranged on the surface protection layer, wherein the groove and the oxidation hole penetrate the surface protection layer, and the upper insulating layer may cover the groove and the oxidation hole.

[0053] Furthermore, the VCSEL may further include: a plurality of through holes penetrating the upper insulating layer and the surface protection layer to expose the ohmic contact layer, wherein the through holes may be arranged to correspond to the protrusions.

[0054] The VCSEL may further include a pad and a connection portion disposed on the upper insulating layer, the pad being disposed outside the trench, and the connection portion extending from the pad to be electrically connected to the ohmic contact layer through the through hole.

[0055] According to another embodiment of the present disclosure, a vertical cavity surface emitting laser having an emitter array is provided. The VCSEL includes: a lower mirror; an upper mirror; an active layer, which is arranged between the lower mirror and the upper mirror; a hole-forming layer, which is arranged between the upper mirror and the active layer and has an oxide layer and a window layer surrounded by the oxide layer; an annular groove, which passes through the upper mirror, the hole-forming layer and the active layer and defines an isolation area inside; and a plurality of oxide holes, which are arranged in the isolation area surrounded by the groove and pass through the upper mirror and the hole-forming layer, wherein the emitter array is arranged in the isolation area surrounded by the groove, and the plurality of oxide holes are arranged to correspond to the emitters in the emitter array.

[0056] The holes can be finely formed by arranging the oxidation holes in the isolation region together with the trenches, and the surface defects can be prevented from moving toward the holes.

[0057] In addition, the groove may be formed through a portion of the thickness from the upper mirror to the lower mirror.

[0058] The VCSEL may further include: an ohmic contact layer arranged on the upper mirror corresponding to each emitter, wherein each ohmic contact layer includes a circular portion in a circular ring shape and a plurality of protrusions protruding to the outside of the circular portion, and the oxidation holes may be arranged between the protrusions.

[0059] According to an embodiment, the circular ring shape of the ohmic contact layer may be a partial ring shape with a portion cut off.

[0060] In another embodiment, the ohmic contact layer may have a symmetrical structure, and the protrusions are spaced apart from each other at the same interval.

[0061] The VCSEL may further include: a surface protection layer covering the ohmic contact layer and the upper mirror and an upper insulating layer arranged on the surface protection layer, wherein the groove and the oxidation hole penetrate the surface protection layer, and the upper insulating layer may cover the groove and the oxidation hole.

[0062] The VCSEL may further include: a plurality of through holes penetrating the upper insulating layer and the surface protection layer to expose the ohmic contact layer, wherein the through holes are arranged to correspond to the protrusions.

[0063] The VCSEL may further include a pad and a connection portion disposed on the upper insulating layer, wherein the pad is disposed outside the trench, and the connection portion may extend from the pad to be electrically connected to the ohmic contact layer through the through hole.

[0064] Further, the connection portion may have a mesa shape including circular opening portions corresponding to the respective emitters.

[0065] In addition, the oxidation pores may have an elliptical, circular, or quadrilateral shape.

[0066] Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0067] Figure 1 is a schematic plan view of a VCSEL according to an embodiment of the present disclosure, Figure 2A It is enlarged to show Figure 1 A schematic plan view of the transmitter region, Figure 2B is along Figure 2A A schematic cross-sectional view taken along the cutting line AA.

[0068] Reference Figure 1 , Figure 2A and Figure 2B , the VCSEL 100 may include an emitter 150, a pad 40, and a connection portion 41. The emitter 150 includes a lower lens 25, an active layer 27, an aperture forming layer 29, and an upper lens 31. The VCSEL 100 may also include a substrate 21, a buffer layer 23, an ohmic contact layer 33, a surface protection layer 35, an upper junction layer 39, and a lower electrode 51. The VCSEL 100 may also include: a groove 37; and an isolation region surrounded by the groove 37; and an oxidation hole 29a arranged in the isolation region.

[0069] The substrate 21 may be a conductive substrate, for example, a semiconductor substrate such as n-type GaAs. The substrate 21 may also be a growth substrate for growing a semiconductor layer arranged thereon, and may be selected according to the semiconductor layer to be grown.

[0070] The buffer layer 23 may be formed to help the growth of the semiconductor layer, but may also be omitted. In the case where the substrate 23 is a GaAs substrate, the buffer layer 23 may be, for example, a GaAs layer.

[0071] The lower mirror 25 may have a distributed Bragg reflector structure and may include an n-type semiconductor layer. The lower mirror 25 may be formed by, for example, repeatedly stacking semiconductor layers having different refractive indices. For example, the lower mirror 25 may be formed by alternately stacking AlGaAs layers having a relatively low Al content and AlGaAs layers having a relatively high Al content. In particular, the lower mirror 25 may be formed by alternately stacking Al0.15Ga0.85As layers having an Al content of 15% and Al0.85Ga0.15As layers having an Al content of 85%. The lower mirror 25 may be formed by stacking approximately 1 to 3×10 18 / cm 3 The lower mirror 25 may include, for example, more than 30 pairs of semiconductor layers having different refractive indices from each other. The thickness of each layer in the lower mirror 25 may be set to 1 / 4 of the wavelength of light in each layer. A pair of semiconductor layers having different refractive indices from each other may have a thickness in the range of about 100 nm to 200 nm.

[0072] The active layer 27 can be arranged on the lower mirror 25 and can be connected to the lower mirror 25. The active layer 27 can have a barrier layer and a well layer, and can have a structure in which the well layer is arranged between the barrier layers. The active layer 27 can especially have a multiple quantum well structure with multiple well layers, and can include, for example, a stacked structure of GaAs / InGaAs / GaAs. The composition of the barrier layer and the well layer can be changed according to the required laser wavelength, and the well layer can include, for example, a four-component system, a three-component system or a two-component system of the InAlGaAs type. In addition, although the present disclosure is described using GaAs as an example, it is not limited to this, and semiconductor layers of the InAlGaN type or the InAlGaP type can also be used, and accordingly, the barrier layer and the well layer can also have a nitride type or a phosphide type composition.

[0073] The well layer in the active layer 27 is formed by a non-doped layer, and the barrier layer can also be formed by a non-doped layer. The thickness of the well layer can be about 2nm to 8nm, and the thickness of the barrier layer can be in the range of about 2nm to 15nm.

[0074] The upper mirror 31 is arranged on the active layer 27. The upper mirror 31 has a distributed Bragg reflector structure and may include a p-type semiconductor layer. The upper mirror 31 may be formed, for example, by repeatedly stacking semiconductor layers having different refractive indices from each other. For example, the upper mirror 31 may be formed by alternately stacking AlGaAs layers with a relatively low Al content and AlGaAs layers with a relatively high Al content. In particular, the upper mirror 31 may be formed by alternately stacking Al0.15Ga0.85As layers with an Al content of 15% and Al0.85Ga0.15As layers with an Al content of 85%. For example, the upper mirror 31 may be formed by alternately stacking about 1 to 5×10 18 / cm 3 The upper mirror 31 may include about 20 or more pairs of semiconductor layers having different refractive indices from each other. However, the number of pairs in the upper mirror 31 is less than that in the lower mirror 25. In addition, the thickness of each layer may be set to 1 / 4 of the wavelength of light in each layer.

[0075] In addition, the aperture forming layer 29 is arranged between the active layer 27 and the upper mirror 31. The aperture forming layer 29 may include an oxide layer 29x and a window layer 29w. The window layer 29w is surrounded by the oxide layer 29x, thereby forming an aperture that limits the path of the current. The aperture forming layer 29 may be formed using, for example, an AlGaAs layer having a higher Al content than the layer in the upper mirror 31. For example, the Al content in the aperture forming layer 29 may be about 90% or more. The oxide layer 29x is formed by oxidizing the AlGaAs layer in a region other than the window layer 29w.

[0076] The width of the hole formed through the oxide layer 29 x , ie, the window layer 29 w is not particularly limited, and may be, for example, in the range of 3 μm to 12 μm.

[0077] Although in Figure 2A 2 shows a case where the window layer 29w or the hole has a disk shape, but the invention is not necessarily limited thereto. Although the window layer 29w may be in a disk shape, it may also be in other shapes such as a polygonal shape similar to a disk.

[0078] The ohmic contact layer 33 is disposed on the upper mirror 31. In particular, the ohmic base layer 33 may ohmically contact the upper mirror 31 on an isolated region surrounded by the groove 37. The ohmic contact layer 33 may include, for example, Ti, Pt, and Au, and may form the ohmic contact using a rapid thermal process. Figure 2A As shown, the ohmic contact layer 33 may include a partially annular circular portion 33a and a protrusion 33b protruding outside the circular portion. The protrusion 33b may be provided to increase a connection area of ​​the pad 40.

[0079] The surface protection layer 35 can protect the upper mirror 31 and the ohmic contact layer 33 during the formation of the groove 37. The surface protection layer 35 can be used as an etching mask in particular. The surface protection layer 35 is formed using a light-transmitting material, and can be formed using, for example, a silicon oxide film or a silicon nitride film. The surface protection layer 35 can also be formed with a thickness of an integer multiple of 1 / 4 of the wavelength of light in the surface protection layer. For example, in the case where the surface protection layer 35 is formed of Si3N4, it can be formed to a thickness of an integer multiple of about 118nm. In addition, the surface protection layer 35 can be formed to have a tensile strain, and for this purpose, it can be formed at, for example, 250°C.

[0080] The groove 37 penetrates the upper mirror 31, the hole-forming layer 29, and the active layer 17, and may penetrate a portion of the thickness of the lower mirror 25. The groove 37 may be formed in a ring shape and define an isolation region inside, in which the emitter 150 is formed. The width of the groove 37 may be formed in a range of, for example, 20 μm to 30 μm, but is not particularly limited thereto. Furthermore, although the shape of the groove 37 is that the outer side wall has a circular shape and the inner side includes a concave portion and a protruding portion, it is not limited thereto and may be formed in a ring shape of various shapes.

[0081] Although Figure 2B FIG. 3 shows a case where the region other than the window layer 29w is the oxide layer 29x, but a non-oxide layer such as the window layer 29w may remain outside the trench 37. In the hole-forming layer 29 in the isolation region surrounded by the trench 37, except for the window layer 29w, all are oxidized to become the oxide layer 29x.

[0082] The trench 37 improves light efficiency by preventing current supplied to the emitter 150 from flowing to other regions except the hole (window layer 29 w ).

[0083] Oxidation holes 29a are formed to expose hole-forming layer 29. Oxidation holes 29a may penetrate upper mirror 31 and hole-forming layer 29, and further, may penetrate active layer 27 and penetrate a portion of the thickness of lower mirror 25. Oxidation holes 29a may also penetrate surface protection layer 35.

[0084] The oxidation hole 29a is arranged outside the ohmic contact layer 33, and in particular, can be arranged between the protrusions 33b. Further, the oxidation hole 29a is formed on an isolated region surrounded by the groove 37. By arranging the oxidation hole 29a on an isolated region separated from the groove 37, it is possible to prevent defects generated by forming the groove 37 from moving to the hole during the formation of the oxidation layer 29x. In addition, by forming the ohmic contact layer 33 to have the protrusion 33b, the oxidation holes 29a can be arranged closer to each other, thereby reducing the size of the emitter 150.

[0085] Furthermore, the oxidation holes 29a may be formed to have sizes smaller than the sizes of the protrusions 33b, respectively. For example, the plane area of ​​the oxidation holes 29a may be smaller than the plane area of ​​the protrusions 33b. The size of the oxidation holes 29a may be made relatively small, thereby suppressing moisture penetration through the oxidation holes after the oxide layer is formed. For example, the depth of the oxidation holes 29a may be about 3 μm, and the hole diameter may be about 4 μm.

[0086] The oxide hole 29a is used to oxidize the hole forming layer 29, thereby defining the oxide layer 29x and the window layer 29w. At this time, the upper mirror 31, the active layer 27 and the lower mirror 25 exposed to the side wall of the oxide hole 29a can also be partially oxidized. According to this embodiment, the oxide hole 29a can be used to form a hole instead of using the groove 37 to form a hole, so that the size of the isolation area can be relatively large while finely forming a small-sized hole, and the time required for the oxidation process can be saved. Further, since the size of the isolation area can be relatively large, the width of the ohmic contact layer 33 can be made relatively large, and in particular, the protrusion 33b can be formed, thereby increasing the connection area of ​​the pad 40.

[0087] The upper insulating layer 39 covers the surface protection layer 35 and covers the groove 37 and the oxidation hole 29a. The upper mirror 35, the oxide layer 29x, the active layer 27 and the lower mirror 25 exposed in the groove 37 and the oxidation hole 29a can be covered and insulated by the upper insulating layer 39. The upper insulating layer 39 can be formed using a light-transmitting material, for example, it can be formed using a silicon oxide film or a silicon nitride film. The upper insulating layer 39 can also be formed with a thickness of an integral multiple of 1 / 4 of the wavelength of light in the upper insulating layer. For example, when the upper insulating layer 39 is formed using Si3N4, it can be formed to a thickness of approximately 200nm, 300nm or 500nm. In addition, the upper insulating layer 39 can be formed to have a tensile strain, and for this purpose, it can be formed at, for example, 250°C.

[0088] In addition, a through hole 39a is formed to penetrate the upper insulating layer 39 and the surface protection layer 35 to expose the ohmic contact layer 33. The through hole 39a is arranged to correspond to the protrusion 33b of the ohmic contact layer 33. Figure 2A As shown, the through hole 39a may be formed to expose the protrusion 33b and the circular portion 33a together. Figure 2A 3 shows a case where the through holes 39a are quadrilateral, but their shapes are not particularly limited and may also be circular.

[0089] In addition, pads 40 and connecting portions 41 may be arranged on the upper insulating layer 39. The pads 40 are arranged over a relatively wide area as an area for bonding wires. The pads 40 may be arranged, for example, outside the grooves 37, and thus, parasitic capacitance may be reduced.

[0090] In addition, the connection part 41 electrically connects the pad 40 and the ohmic contact layer 33. The connection part 41 may be connected to the ohmic contact layer 33 through the through hole 39a. The connection part 41 may have a partially annular circular portion along the ohmic contact layer 33, and an opening part 41a that can emit a laser beam is provided inside the annular circular portion.

[0091] The pad 40 and the connection portion 41 may be formed of the same metal material, for example, Ti / Pt / Au. The pad 40 and the connection portion 41 may be formed to have a thickness of about 2 μm or more.

[0092] In addition, the lower electrode 51 is arranged at the lower part of the substrate 21, and can be used as, for example, an n-pad. In the case where the substrate 21 is a GaAs substrate, as an example, the lower electrode 51 can be formed of AuGe / Ni / Au

[0093] Figure 3A , Figure 3B , Figure 4A , Figure 4B , Figure 5A as well as Figure 5B Schematic plan view and cross-sectional view for explaining a method for manufacturing a VCSEL according to an embodiment of the present disclosure. Each cross-sectional view is a view taken along the section line AA of the corresponding plan view.

[0094] First, refer to Figure 3A and Figure 3B , semiconductor layers 23 , 25 , 27 , 29 , and 31 are formed on a substrate 21 , and an ohmic contact layer 33 is formed.

[0095] The substrate 21 may be, for example, an n-type GaAs substrate. The semiconductor layer may include a buffer layer 23, a lower mirror 25, an active layer 27, a hole-forming layer 29, and an upper mirror 31. The semiconductor layer may be formed using epitaxial growth techniques such as metal organic chemical vapor deposition or molecular beam epitaxy.

[0096] The buffer layer 23 can be formed on the substrate 21 using, for example, a GaAs layer. The lower mirror 25 is formed on the buffer layer 23, and an active layer 27, a hole-forming layer 29, and an upper mirror 31 can be sequentially formed on the lower mirror 25. The lower mirror 25 and the upper mirror 31 can be formed by repeatedly stacking AlGaAs / AlGaAs with different Al compositions. Since the specific structures of the lower mirror 25, the active layer 27, the hole-forming layer 29, and the upper mirror 31 have been described in detail previously, their description is omitted here to avoid repetition.

[0097] An ohmic contact layer 33 is formed on the upper mirror 31. The ohmic contact layer 33 is formed to include a partially annular circular portion 33a and a protrusion 33b protruding from the circular portion 33a to the outside. For the ohmic contact layer 33, a metal layer can be formed by a lift-off technique and then heat-treated by a rapid thermal process. The metal layer can be formed by, for example, Ti / Pt / Au, and can be formed to a thickness of about 300, 300, and 1000 to 3000, respectively. Through the thermal treatment, a good ohmic contact can be formed between the ohmic contact layer 33 and the upper mirror 31.

[0098] Although the present embodiment shows a case where one ohmic contact layer 33 is formed on the upper portion of the substrate 21 , the substrate 21 may have a diameter of, for example, 10 mm, and a plurality of ohmic contact layers 33 may be formed on the substrate 21 in each element region.

[0099] Also, although the ohmic contact layer 33 may be formed by using a negative photoresist or a positive photoresist as a mask, the positive photoresist is more suitable for forming a high-density array.

[0100] Reference Figure 4A and Figure 4B A surface protection layer 35 is formed to cover the upper mirror 31 and the ohmic contact layer 33. The surface protection layer 35 protects the upper mirror 31 during the formation of the groove 37 and the oxidation hole 29a.

[0101] The surface protection layer 35 can be formed of, for example, Si3N4 or SiO2, and can be formed to a thickness that is an integral multiple of 1 / 4 of the wavelength of light in the surface protection layer 35. For example, when the surface protection layer 35 is formed of Si3N4, the thickness can be formed to be an integral multiple of about 118nm.

[0102] Next, a photoresist is formed on the surface protection layer 35 and an etching process is performed using the photoresist as a mask, thereby forming a groove 37 and an oxidation hole 29a. An isolation region surrounded by the groove 37 is formed by the groove 37, and the oxidation hole 29a is arranged around the ohmic contact layer 33 in the isolation region and is separated from the groove 37. The photoresist can be removed after the etching process is completed.

[0103] The groove 37 and the oxidation hole 29 a may penetrate the surface protection layer 35 , the upper mirror 31 , the hole-forming layer 29 , the active layer 27 , and may penetrate a portion of the thickness of the lower mirror 25 .

[0104] Further, the oxidation hole 29a may be arranged between the protrusions 33b and have a size smaller than the protrusions 33b. The oxidation hole 29a has a depth of about 3 μm, a diameter (or width) of about 4 μm at the inlet side, and a side wall that is inclined at about 80 degrees. The shape of the oxidation hole 29a may be various, which will be referred to later. 9A to 9C The ohmic contact layer 33 is formed to have the protrusion 33 b so that the width of the circular portion 33 a can be reduced, thereby reducing the interval between the oxidation holes 29 a.

[0105] Next, the hole-forming layer 29 exposed through the oxidation hole 29a is oxidized. The oxidation may be performed, for example, in the range of 400°C to 430°C, and the Al composition ratio of the hole-forming layer 29 may be adjusted and the temperature and composition may be set to show an oxidation rate 10 times or more compared to the layers in the lower mirror 25 and the upper mirror 31.

[0106] Through the oxidation process, an oxide layer 29x is formed in the hole-forming layer 29 around the groove 37 and the oxide hole 29a. The oxidation proceeds toward the inside of the hole-forming layer 29 through the groove 37 and the hole-forming layer 29 exposed at the inner wall of the oxide hole 29a. Accordingly, a window layer (hole) 29w is formed in the lower part of the region surrounded by the ohmic contact layer 33. In addition, as Figure 4B As shown, a portion of the oxide layer 29 x may also be formed in the outer region of the trench 37 .

[0107] Since oxidation is performed at a relatively high temperature of 400° C. to 430° C., surface defects generated when forming the trench 37 can move. At this time, since the oxidation holes 29a are arranged in the isolation region, the defects can be prevented from moving to the window layer 29w side.

[0108] Reference Figure 5A and Figure 5B , an upper insulating layer 39 is formed on the surface protection layer 35. The upper insulating layer 39 can be formed of a light-transmitting material, for example, can be formed of Si3N4 or SiO2. The upper insulating layer 39 covers the sidewalls and bottom of the trench 37 and the oxidation hole 29a, thereby insulating the semiconductor layer exposed in the trench 37 and the oxidation hole 29a.

[0109] In addition, a through hole 39a exposing the ohmic contact layer 33 is formed by patterning the upper insulating layer 39 and the surface protection layer 35. Figure 5A As shown, the through hole 39 a may be formed corresponding to the protrusion 33 b of the ohmic contact layer 33 .

[0110] Although not shown in the figure, when forming the through hole 39a, an element separation region, for example, a scribe line, for separating elements of a plurality of element regions formed on the substrate 21 can be formed together. The scribe line is formed by etching the surface protection layer 35 and the upper insulating layer 39, and can prevent the surface protection layer 35 and the upper insulating layer 39 from being peeled off when a dicing process for separating elements is performed later.

[0111] Next, form Figure 1 The pad 40 and the connecting portion 41 are shown. The pad 40 and the connecting portion 41 can be formed by lift-off technology, and can be formed by, for example, Ti / Pt / Au. In addition, a lower electrode 51 can be formed on the lower surface of the substrate 21.

[0112] Thereafter, the individual components are separated along the scribe lines to complete the Figure 1 VCSEL.

[0113] Figure 6 is a schematic plan view of a VCSEL according to yet another embodiment of the present disclosure, Fig. 7A It is enlarged to show Figure 6 A schematic plan view of a portion of a transmitter array, Figure 7B is along Fig. 7A The cross-sectional view taken along the interception line BB of Figure 7C is along Fig. 7A Cross-sectional view taken along the interception line CC.

[0114] Reference Figure 6 , Fig. 7A , Figure 7B and Figure 7C The VCSEL 200 according to this embodiment is different from the reference Figure 1 , Figure 2A as well as Figure 2B The VCSEL 100 described is generally similar, but differs in that it includes a plurality of emitter arrays 250, and accordingly, the shapes of the grooves 37 and the pads 40 are deformed. In order to avoid repetition, detailed descriptions of the same contents are omitted.

[0115] The groove 37 is formed in a ring shape and defines an isolation area inside. The emitter array 250 can be arranged in the isolation area surrounded by the ring-shaped groove 37, and the pad 40 is located outside the groove 37. The emitters in the emitter array 250 can be arranged in a honeycomb shape, for example, as shown in the figure.

[0116] The pad 40 may be adjacent to the array region 250 and formed on one side of the substrate 21. Figure 6 As shown in FIG. 1 , in this embodiment, the pad 40 can be arranged over a wide area outside the groove 37, so that it is easy to connect electrically. However, the present disclosure is not necessarily limited to this, and can also be arranged in a manner similar to that of FIG. Figure 1 A similar shape is formed with pad 40 .

[0117] In addition, the groove 37 is formed with a width wider than the thickness of the pad 40. For example, the pad 40 may be formed with a thickness of 2 to 6 μm, and the groove 37 may be formed with a relatively wide width of 20 to 30 μm. Accordingly, the groove 37 can prevent the connection portion 41 from being short-circuited.

[0118] like Fig. 7A As shown, an ohmic contact layer 33, an oxidation hole 29a, and a through hole 39a are formed in each emitter region, and an opening 41a that can emit laser light is formed in the connecting portion 41. Figure 1 , Figure 2A as well as Figure 2B As shown, the emitter array 250 includes a lower mirror 25, an active layer 27, a hole-forming layer 29, and an upper mirror 31. In addition, the hole-forming layer 29 includes an oxide layer 29x and a window layer 29w. Except for the window layer 29w, the hole-forming layers 29 in the emitter array 250 are all oxide layers 29x, so the flow of current is limited to the window layer 29w. The basic structure of each emitter in the emitter array 250 is the same as the emitter 150 described previously.

[0119] An ohmic contact layer 33 may be formed in each emitter. As previously described, the ohmic contact layer 33 may include a partially annular circular portion 33a and a protrusion 33b. Also, in each emitter region, an oxidation hole 29a is arranged between the protrusions 33b, and a through hole 39a is formed corresponding to the protrusion 33b. The oxidation hole 29a and the through hole 39a formed in each emitter are the same as those formed in the emitter 150 of the previously described embodiment. In particular, by forming the oxidation hole 29a separately in each emitter, the size of the oxidation hole 29a can be made smaller than the size of the protrusion 33b, thereby improving the reliability of the element.

[0120] In addition, the connection pad 40 and the connection portion 41 of the ohmic contact layer 33 can be connected to each emitter through the through hole 39a. The emitters can be connected in parallel. However, although the connection portion 41 has a partial ring shape in the previous embodiment, it can have a table shape forming a circular opening portion 41a as shown in the figure.

[0121] Furthermore, the connection portion 41 may also completely cover the groove 37 , thereby further preventing the connection portion 41 from being disconnected in the groove 37 .

[0122] Since the method for manufacturing the VCSEL 200 having the emitter array 250 is substantially similar to the method for manufacturing the VCSEL 100 described previously, a detailed description thereof will be omitted.

[0123] According to this embodiment, the emitters in the emitter array 250 are not separated from each other by the grooves. Therefore, it is possible to prevent the connection portion 41 from being disconnected in the grooves with significant step differences. Further, it is possible to prevent the window layer 29w from being damaged due to surface defects caused by the formation of the grooves, thereby providing a highly reliable emitter array.

[0124] Figure 8 It is a schematic plan view for explaining a modification example of the ohmic contact layer.

[0125] Reference Figure 8 , while the ohmic contact layer 33 in the previous embodiment includes a partially annular circular portion 33a and a protrusion 33b, in this embodiment, the ohmic contact layer 133 includes an annular circular portion 133a and a protrusion 133b. That is, in this embodiment, the circular portion 133a has a predetermined width and a closed circular ring shape, and the protrusions 133b are arranged to be spaced apart from each other at a predetermined interval and symmetrically. The oxidation holes are arranged between the protrusions 133b.

[0126] By forming the ohmic contact layer 133 symmetrically, the hole 29 w formed inside can be formed into a shape closer to a circle.

[0127] In the previous embodiment, the oxidation holes 29a are arranged around the ohmic contact layer 33 and have an elliptical shape. The major axes of the oxidation holes 29a are arranged in a direction perpendicular to a straight line connecting the center of the emitter 150 and the center of the oxidation hole 29a. Therefore, the shape of the window layer (hole) 29w surrounded by the oxidation layer 29x formed by the oxidation hole 29a is approximately similar to a circle.

[0128] However, the present disclosure does not limit the shape of the oxidation hole 29 a to an ellipse, and the shape of the oxidation hole 29 a may be variously modified. 9A to 9C Schematic plan views for explaining various modified examples of oxide holes for forming an oxide layer.

[0129] like Fig. 9A As shown, the oxidation hole 29b may have a circular shape. The elliptical or circular oxidation holes 29a, 29b are easy to pattern and can improve the stability of the upper insulating layer 39 or the connecting portion 41 formed thereon. Fig. 9B As shown, the oxidation holes 29c have a square or rectangular shape and can be arranged at positions corresponding to the vertices of a regular hexagon. Fig. 9C As shown, the oxidation hole 29c has a quadrangular shape, and the side near the center of the emitter may be formed concavely.

[0130] Also, although not shown, the number of oxidation holes around the center of the emitter may be arranged to be greater than 6, whereby the shape of the holes may be made closer to a circle.

[0131] Although various embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments. Furthermore, the content or constituent elements described in one embodiment may be applied to other embodiments as long as they do not deviate from the technical concept of the present disclosure.

Claims

1. A vertical cavity surface emitting laser, characterized in that: include: Lower mirror; Upper mirror; an active layer disposed between the lower mirror and the upper mirror; an annular groove, penetrating the upper mirror and the active layer and defining an isolation area inside; an ohmic contact layer disposed on the upper mirror; an upper insulating layer covering the ohmic contact layer and the upper mirror; as well as A connecting portion arranged on the upper insulating layer, Wherein, the upper insulating layer covers the sidewalls and the bottom of the trench, The connecting portion defines a circular opening portion inside which can emit laser light. The connection portion is electrically connected to the ohmic contact layer via a through hole formed in the upper insulating layer, and the connection portion covers a region of the isolation region formed by the trench except a region corresponding to the opening.

2. The vertical cavity surface emitting laser according to claim 1, characterized in that: The groove passes through a portion of the thickness of the lower mirror.

3. The vertical cavity surface emitting laser according to claim 1, characterized in that: The ohmic contact layer includes a circular portion in a circular ring shape and a plurality of protrusions protruding to an outer side of the circular portion.

4. The vertical cavity surface emitting laser according to claim 3, characterized in that: The circular ring shape is a partial ring with a portion cut off.

5. The vertical cavity surface emitting laser according to claim 3, characterized in that: The ohmic contact layer has a symmetrical structure, and the protrusions are spaced apart from each other at the same interval.

6. The vertical cavity surface emitting laser according to claim 3, characterized in that: Also includes: a surface protection layer covering the ohmic contact layer and the upper mirror, wherein the upper insulating layer is arranged on the surface protection layer, The groove passes through the surface protection layer.

7. The vertical cavity surface emitting laser according to claim 6, characterized in that: The through holes are formed in plurality and penetrate the upper insulating layer and the surface protection layer to expose the ohmic contact layer. Wherein, the through hole is arranged to correspond to the protrusion.

8. The vertical cavity surface emitting laser according to claim 7, characterized in that: Also includes: a pad disposed on the upper insulating layer, wherein the pad is arranged outside the groove, The connection portion extends from the pad to be electrically connected to the ohmic contact layer through the through hole.

9. A vertical cavity surface emitting laser having an emitter array, characterized in that: include: Lower mirror; Upper mirror; an active layer disposed between the lower mirror and the upper mirror; an annular groove, penetrating the upper mirror and the active layer and defining an isolation area inside; an ohmic contact layer arranged on the upper mirror corresponding to each emitter of the emitter array; an upper insulating layer covering the ohmic contact layer and the upper mirror; as well as A connecting portion arranged on the upper insulating layer, wherein the emitter array is arranged in an isolated area surrounded by the groove, The upper insulating layer covers the sidewalls and bottom of the trench, The connection portion defines a circular opening portion capable of emitting laser light corresponding to each emitter of the emitter array. The connection portion is electrically connected to the ohmic contact layer via a through hole formed in the upper insulating layer, and the connection portion covers a region of the isolation region formed by the trench except a region corresponding to the opening.

10. The vertical cavity surface emitting laser according to claim 9, characterized in that: The groove is formed through a portion of the thickness from the upper mirror to the lower mirror.

11. The vertical cavity surface emitting laser according to claim 9, characterized in that: Each ohmic contact layer includes a circular portion in a circular ring shape and a plurality of protrusions protruding to the outside of the circular portion.

12. The vertical cavity surface emitting laser according to claim 11, characterized in that: The circular ring shape of the ohmic contact layer is a partial ring shape with a portion cut off.

13. The vertical cavity surface emitting laser according to claim 11, characterized in that: The ohmic contact layer has a symmetrical structure, and the protrusions are spaced apart from each other at the same interval.

14. The vertical cavity surface emitting laser according to claim 11, characterized in that: Also includes: a surface protection layer covering the ohmic contact layer and the upper mirror, wherein the upper insulating layer is arranged on the surface protection layer, The groove passes through the surface protection layer.

15. The vertical cavity surface emitting laser according to claim 14, characterized in that: The through holes are formed in plurality and penetrate the upper insulating layer and the surface protection layer to expose the ohmic contact layer. Wherein, the through hole is arranged to correspond to the protrusion.

16. The vertical cavity surface emitting laser according to claim 15, characterized in that: Also includes: a pad disposed on the upper insulating layer, wherein the pad is arranged outside the groove, The connection portion extends from the pad to be electrically connected to the ohmic contact layer through the through hole.

17. The vertical cavity surface emitting laser according to claim 16, characterized in that: The connection portion has a table shape including circular openings corresponding to the respective emitters.

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