KR19990086323A - Short wavelength surface emitting semiconductor laser diode and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a short wavelength surface-emitting semiconductor laser diode using GaN-based Group III-V group nitrides and a method of manufacturing the same. The short wavelength surface-emitting semiconductor laser diode and a method of manufacturing the same according to the present invention include a current limiting layer directly above and below or on one side of the resonator, and in order to effectively limit the current, the current limiting layer is formed of an air layer from which AlN is removed. By concentrating the light, the efficiency of the light emitted is increased, and the optical waveguide effect by the air layer is obtained.

Description

Short wavelength surface-emitting semiconductor laser diode and manufacturing method thereof

The present invention relates to a short wavelength surface-emitting semiconductor laser diode using GaN-based Group III-V group nitrides, and more particularly, to a structure in which an upper metal electrode and a lower metal electrode are directly contacted with a resonator, thereby enabling effective current limiting and optical waveguide. It relates to a short wavelength surface-emitting semiconductor laser diode having a and a method of manufacturing the same.

In general, the surface-emitting semiconductor laser diode has a structure having a distributed Bragg reflector (DBR) having a reflectance of 99% or more on the upper and lower portions of the active layer to cause the light to resonate in the vertical direction of the stacks. The DBR has a lamination structure in which a material having a large difference in refractive index and similar lattice constants, such as GaAs and AlAs, is deposited alternately with epitaxial growth, or SiO ₂ , Al ₂ O _3, and TiO ₂ . It has a structure in which pairs of materials having a large difference in refractive index among the same insulating materials are selected and alternately stacked. The DBR has a greater bandgap energy than the oscillation wavelength, so no absorption should occur, and a larger refractive index difference between the two DBR materials is advantageous.

GaN, AlGaN, or AlN may be used as a semiconductor material in the GaN semiconductor laser diode mainly used to generate blue-based short wavelength light as a DBR. AlGaN and AlN having an Al content of 30% or more have a bandgap energy that is too large, and when a current is injected through a DBR composed of the compound, the driving voltage becomes very high and there is a concern that heat generation may occur. Therefore, the surface-emitting semiconductor laser diode formed of the above materials must be manufactured so that the current limiting structure and the optical waveguide structure have a different structure than the conventional GaAs-based surface-emitting semiconductor laser diode.

SUMMARY OF THE INVENTION The present invention has been made to improve the above problems, and provides a short wavelength surface emitting semiconductor laser diode having a current limiting layer which connects metal electrodes directly to a resonator and enables effective current limiting, and a method thereof. There is this.

1 and 2 are vertical cross-sectional views after the step-by-step process of manufacturing a short wavelength surface-emitting semiconductor laser diode according to the present invention,

1 is a vertical cross-sectional view after forming the DBR structure,

2 is a vertical cross-sectional view after completing the device by performing the current limiting structure and metal electrode formation,

3 is a vertical cross-sectional view showing yet another embodiment of a short wavelength surface emitting semiconductor laser diode according to the present invention.

<Description of the symbols for the main parts of the drawings>

11. Lower Dispersion Bragg Reflector (DBR) 11a. GaN / Al _y Ga _1-y N layer

11b. AlGaN / Al _x Ga _1-x N layer 12.n-GaN contact layer

13. n-Al _x Ga _1-x N carrier confinement layer 14.In _x Ga _1-x N active layer

15.p-Al _x Ga _1-x N carrier confinement layer 16.AlN / Al _x Ga _1-x N layer

17. p-GaN contact layer 18. Top Dispersion Bragg Reflector (DBR)

18a. GaN / Al _y Ga _1-y N layer 18b. AlGaN / Al _x Ga _1-x N layer

21. Lower Dispersion Bragg Reflector (DBR) 21a. GaN / Al _y Ga _1-y N layer

21b. AlGaN / Al _x Ga _1-x N layer 22.n-GaN contact layer

23.n-Al _x Ga _1-x N Carrier Limiting Layer 24.In _x Ga _1-x N Active Layer

25. p-Al _x Ga _1-x N carrier confinement layer 26 '. AlN / Al _x Ga _1-x N conduction channel layer

26 ". Current limiting layer (air layer) 27. p-GaN contact layer

28. Upper Dispersion Bragg Reflector (DBR) 28a. GaN / Al _y Ga _1-y N layer

28b. AlGaN / Al _x Ga _1-x N layer 29. Top metal electrode

30. Bottom metal electrode 41. Bottom distributed Bragg reflector (DBR) 41a. GaN / Al _y Ga _1-y N layer 41b. AlGaN / Al _x Ga _1-x N layer

42.n-GaN contact layer 43.n-Al _x Ga _1-x N carrier confinement layer

44.In _x Ga _1-x N active layer 45.p-Al _x Ga _1-x N carrier confinement layer

46 '. AlN / Al _x Ga _1-x N conduction channel layer 46 ". Current limiting layer (air layer)

47. p-GaN contact layer 48. Top dispersed Bragg reflector (DBR 48a.GaN / Al _y Ga _1-y N layer 48b.AlGaN / Al _x Ga _1-x N layer

49. Upper metal electrode 50. Lower metal electrode

In order to achieve the above object, the short wavelength surface emitting semiconductor laser diode according to the present invention is a short wavelength surface emitting semiconductor laser diode having a lower distributed Bragg reflector, a resonator, and an upper distributed Bragg reflector on a semiconductor substrate, And an energization channel layer for supplying current to the resonator in at least one of the upper parts, and forming a current limiting layer having an outer layer of the energization channel as an air layer to narrow the planar size of the energization channel to the narrower than the upper dispersion Bragg reflector. The total thickness of the resonator including the conducting channel layer is formed to be nλ when the conduction channel layer is included in the resonator when the wavelength of the oscillating light is limited to a predetermined size and n is any integer. do.

In the present invention, the resonator including the conduction channel layer, the active layer formed of a multi-quantum well layer of In _x Ga _1-x N; An n-Al _x Ga _1-x N lower carrier limiting layer and a p-Al _x Ga _1-x N upper carrier limiting layer for carrier limitation respectively below and above the active layer; And a conducting channel layer formed of AlN or Al _x Ga _1-x N, wherein an n-GaN lower contact layer and a p-GaN upper contact for electrode connection are respectively formed on the upper and lower portions of the resonator including the conducting channel layer. And a metal electrode formed at an upper edge of the n-GaN lower contact layer and the p-GaN upper contact layer so as to be spaced apart from the upper distributed Bragg reflector and the resonator, respectively. A lamination layer of a relatively high refractive index GaN layer and a relatively small refractive index AlGaN layer is repeatedly stacked, or a relatively large refractive index Al _y Ga _1-y N layer and a relatively small refractive index Al _x Ga _1-x N The layers are formed by alternately stacking a plurality of times (x &gt; y), wherein the lower distributed Bragg reflector, the resonator and the upper distributed Bragg reflector are respectively the lower distributed Bragg reflector, the resonator and the image. It is preferably formed in a cylindrical or polygonal cylinder with a large diameter in the order of the secondary dispersion Bragg reflector, the conduction channel layer is preferably formed so that the diameter ranges from 10 to 200 μm, the reflectance of the lower dispersion Bragg reflector to the upper dispersion Bragg The laser beam is formed to be emitted from the upper distributed Bragg reflector by being larger than the reflector of the reflector, or the laser beam is emitted from the lower distributed Bragg reflector by making the reflectance of the upper distributed Bragg reflector larger than the reflectance of the lower distributed Bragg reflector. It is preferable.

In addition, in order to achieve the above object, the method for manufacturing a short wavelength surface-emitting semiconductor laser diode according to the present invention includes (a) a preliminary lower distributed Bragg reflector, a preliminary resonator layer, and a preliminary upper distributed Bragg reflector layer sequentially on a semiconductor substrate. Growing and then etching the preliminary upper dispersed Bragg reflector layer into a cylindrical shape by a first dry etching method to form an upper dispersed Bragg reflector; (B) etching the preliminary resonator layer into a cylindrical shape having a diameter larger than that of the upper dispersed Bragg reflector by a second dry etching method to form a resonator layer; (C) etching the preliminary lower distributed Bragg reflector layer into a cylindrical shape having a diameter larger than that of the resonator layer by a third dry etching method to form a lower distributed Bragg reflector; And (d) forming a current confined layer formed of an air layer on the outer side of the conducting channel layer by removing the conduction channel layer included in the resonator layer by etching it from a side surface thereof.

In the present invention, in the step (a), the preliminary lower and upper dispersed Bragg reflector layers may each be formed by repeatedly stacking a GaN layer having a relatively high refractive index and an AlGaN layer having a relatively small refractive index, or Al having a relatively large refractive index. _It is formed by repeatedly stacking a _y Ga _1-y N layer and a relatively small Al _x Ga _1-x N layer a plurality of times, the pre-resonator layer is n-Al _x Ga _1-x N lower carrier limiting layer, It is formed by sequentially stacking an In _x Ga _1-x N active layer, a p-Al _x Ga _1-x N upper carrier limiting layer, and an AlN or Al _x Ga _1-x N conduction channel layer, wherein the wavelength of the generated light is λ. When the refractive index of the constituent material of the Bragg reflector layer is n, the stacks of the upper and lower dispersed Bragg reflector layers are alternately stacked by λ / 4n thickness, respectively, and in the step (D), the AlN or Al _x Ga _{1 -x} N conduction channel layer is the top and bottom distributed Bragg To GaN or Al _y Ga _1-y N and a fraud preventing the etching at the same rate as the high refractive index layer, wherein (a) said upper and lower distributed Bragg reflector in step GaN or Al _y Ga _1-y N and the The refractive index layers are formed such that the molar ratio of Al is smaller than that of the AlN or Al _x Ga _1-x N conducting channel layer, and the preliminary resonator layer has a total of mλ when the wavelength of generated light is λ and an arbitrary integer is m. is formed to a thickness, n-GaN for each metal contact on top of the (a) the lower portion of the _{n-Al x Ga 1-x} n carrier trapping layer in step and the _{p-Al x Ga 1-x} n carrier trapping layer And forming a contact layer and a p-GaN contact layer, and further comprising depositing a metal for an electrode on an upper surface of an edge of the n-GaN contact layer and a p-GaN contact layer after the step (d). It further comprises; The step (d) is preferably made by a wet etching method The.

Hereinafter, a short wavelength surface emitting semiconductor laser diode and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

The surface-emitting semiconductor laser diode according to the present invention is a device for generating a short-wavelength laser beam using GaN-based group 3-5 nitride, and the upper metal electrode and the lower metal electrode are brought into contact with the resonator directly for effective current limiting. The width of the conduction channel layer formed of AlN for restricting the flow of current is etched from the side to form a current limiting layer (air layer) for limiting the width of the conduction channel. The current confined layer made of air has an effect of enabling optical waveguide. These features will be described in detail from the structure as follows.

2 is a vertical cross-sectional view of a short wavelength surface emitting semiconductor laser diode according to the present invention. As shown, the short-wavelength surface-emitting semiconductor laser diode according to the present invention is a layer of a GaN layer 21a having a relatively high refractive index and an AlGaN layer 21b having a relatively low refractive index or a relatively high refractive index on an upper surface of a substrate (not shown). Lower diffused Bragg reflector 21, which is stacked in a layer (x> y) of a high refractive index Al _y Ga _1-y N layer 21a and a relatively low refractive index Al _x Ga _1-x N layer 21b. N-GaN contact layer 22 stacked on distributed Bragg reflector 21, n-Al _x Ga _1-x N lower carrier limiting layer 23, In _x Ga _1-x stacked on n-GaN contact layer 22 N active layer 24, p-Al _x Ga _1-x N upper carrier limiting layer 25 and AlN or Al _x Ga _1-x N conduction channel layer 26 'sequentially stacked resonator, AlN of resonator Or on the p-GaN contact layer 27 and the p-GaN contact layer 27 stacked on the Al _x Ga _1-x N conduction channel layer 26 'and the GaN layer 28a having a relatively high refractive index. Of AlGaN layers 28b having low refractive index Or relative to the refractive index are stacked to a large Al _y Ga _1-y N layer (28a) and relatively gyeopcheung (x> y) of Al _x Ga _1-x N layer (28b) of low refractive index upper distributed Bragg reflector (28 ). Here, the conductive channel layer 26 'of AlN or Al _x Ga _1-x N is etched from the side to form a narrow current path of about 10 to 200 μm. The etched portion of the air layer functions as a current confining layer 26 "and contributes to the optical waveguide. The upper portion of the edge of the n-GaN contact layer 22 and the upper portion of the edge of the p-GaN contact layer 27 are respectively. Metal is deposited to form the lower electrode 30 and the upper electrode 29.

As described above, the short wavelength surface-emitting semiconductor laser diode according to the present invention has a structure in which a metal electrode is directly formed in the resonator including the active layer 24 and the carrier limiting layers 23 and 25 located above and below. The n-GaN contact layer 22 and the p-GaN contact layer 27 are formed on and under the upper portion of the lower electrode 30 and the upper electrode 29 by depositing a p-omic metal or an n-omic metal on the edge thereof. In addition, a portion of the layer formed by depositing AlN or AlGaN on the carrier limiting layer 25 is selectively etched to form a conduction channel so as to limit the current and to form an optical waveguide structure. The AlN or AlGaN conduction channel layer 26 ′ may be formed between the lower contact layer 22 and the n-Al _x Ga _1-x N carrier limiting layer 23, as shown in FIG. 3. It may be formed above and below the resonator.

In addition, the resonator is laminated to a thickness of an integer multiple of the oscillation wavelength in order to satisfy the resonance conditions. In order to emit light emitted above the device, it is preferable to make the reflectance of the upper DBR lower than that of the lower DBR. On the contrary, in order to emit light emitted under the device, the reflectance of the lower DBR is made lower than that of the upper DBR.

The manufacturing method of the short wavelength surface-emitting semiconductor laser diode which has the above structure is as follows.

First, as shown in FIG. 1, a layer of a GaN layer 21a and an AlGaN layer 21b or an Al _y Ga _1-y N layer 21a and Al _x Ga _1-x N on a substrate (not shown). Bottom dispersed Bragg reflector 21, n-GaN contact layer 22, n-Al _x Ga _1-x N bottom carrier confinement layer 23, In _x stacked in a layer (x> y) of layer 21b A resonator consisting of a Ga _1-x N active layer 24, a p-Al _x Ga _1-x N top carrier confinement layer 25 and a conducting channel layer 26 'of AlN or Al _x Ga _1-x N, p- Lamination layer of GaN contact layer 27 and GaN layer 28a and AlGaN layer 28b or lamination layer of Al _y Ga _1-y N layer 28a and Al _x Ga _1-x N layer 28b (x> y The upper dispersion Bragg reflector 28 which consists of) is sequentially laminated (first step).

Next, as shown in FIG. 1, the upper distributed Bragg reflector structural stacks, the resonator stacks, and the lower distributed Bragg reflector stacks, each of which are grown as in the first step, have a predetermined radius. Alternatively, by etching using an etching mask of a polygonal pattern, a cylindrical or polygonal cylindrical upper distributed Bragg reflector 28, a resonator and a lower distributed Bragg reflector 21 are formed (second step). At this time, the diameter of each cylindrical shape is determined so as to leave enough room to form a metal electrode on the edges of the n-contact layer and the p-contact layer. This second step, first, as shown in Figure 1, using a circular or polygonal etching mask, the upper DBR forming sub-step of etching to the p-GaN contact layer 27 by dry etching method, and then more A resonator forming sub-step of etching to the middle of the n-GaN contact layer 22 again by dry etching using a large etching mask; and then etching to a substrate (not shown) by dry etching using a larger etching mask. It consists of a lower DBR forming substep.

Next, as shown in FIG. 2, the AlN or Al _x Ga _1-x N layer 26 positioned on the p-Al _x Ga _1-x N upper carrier limiting layer 25 is replaced with AlN or Al _x Ga _1. Wet etching the side portion with a solution to selectively etch only _-x N to form the energization channel layer 26 '(step 3). At this time, the diameter of the energization channel layer 26 'is determined in the range of 10 to 200 mu m in consideration of the size of the desired laser beam.

Next, as shown in FIG. 2, the n-ohmic metal 30 and p− for current injection are respectively above the edge of the n-GaN contact layer 22 and above the edge of the p-GaN contact layer 27. The ohmic metal 29 is deposited to form a lower electrode and an upper electrode (fourth step). In this way, the device is completed.

As described above, in the method of manufacturing the short wavelength surface-emitting semiconductor laser diode according to the present invention, in the first step, the upper DBR and the lower DBR are composed of GaN and AlGaN or Al _y Ga _1-y N and Al _x Ga _1-x N However, by configuring y <x, the difference in refractive index between the layers is severe, and the reflectance is as high as possible. The aperture of the energization channel layer formed in the third step is adjusted according to the desired beam size and is usually designed to about 10 ~ 200 ㎛. Referring to FIG. 2, since the current is injected through the AlN layer having the upper side of the active layer and etched, the light is only generated in the active layer. In addition, after the AlN layer is etched, air having a refractive index of 1 is filled in the empty space to serve as an optical waveguide. The AlN layer may be replaced with an AlGaN-based compound, and the low refractive index layer is less than the AlN layer 26 to prevent the relative low index layer of the DBR from being etched at the same rate during the etching process. The mole fraction is made small.

As described above, the short-wavelength surface-emitting semiconductor laser diode and a method of manufacturing the same according to the present invention include a current limiting layer directly on the resonator at both upper and lower sides or one side, and the current limiting layer is formed of an air layer from which AlN is removed for effective current limiting. As a result, the efficiency of the light emitted by concentrating the current in the active layer can be increased, and the optical waveguide effect by the air layer can be obtained.

Claims (21)

A short wavelength surface emitting semiconductor laser diode having a lower distributed Bragg reflector, a resonator, and an upper distributed Bragg reflector on a semiconductor substrate, At least one of the lower and upper portions of the resonator having an energization channel layer for supplying current to the resonator, and forming a current confined layer having an outer layer of the energization channel as an air layer so that the planar size of the energization channel is determined by the upper dispersion Bragg. When the wavelength of the oscillating light is λ and n is any integer, the conduction channel layer is included in the resonator, and the total thickness of the resonator including the conduction channel layer is formed to be nλ. A short wavelength surface-emitting semiconductor laser diode, characterized in that. The method of claim 1, The resonator including the conduction channel layer, An active layer formed of a multiple quantum well layer of In _x Ga _1-x N; An n-Al _x Ga _1-x N lower carrier limiting layer and a p-Al _x Ga _1-x N upper carrier limiting layer for carrier limitation respectively below and above the active layer; And Conducting channel layer formed of AlN or Al _x Ga _1-x N; A short wavelength surface emitting semiconductor laser diode, comprising: The method of claim 2, And an n-GaN lower contact layer and a p-GaN upper contact layer for electrode connection respectively above and below the resonator including the energization channel layer. The method of claim 3, And a metal electrode formed at upper edges of the n-GaN lower contact layer and the p-GaN upper contact layer to be spaced apart from the upper distributed Bragg reflector and the resonator, respectively. The method of claim 3, The lower and upper dispersed Bragg reflectors each have a relatively high refractive index GaN layer and a relatively small refractive index layer of AlGaN layer repeatedly stacked a plurality of times, or a relatively large refractive index Al _y Ga _1-y N layer and relatively refractive index A short wavelength surface emitting semiconductor laser diode, wherein the small Al _x Ga _1-x N layers are formed by alternately stacking a plurality of times. The method of claim 3, The upper dispersed Bragg reflector layer and the lower dispersed Bragg reflector layer are short-wave surface light emitting, characterized in that formed by stacking a plurality of pairs of materials having a large difference in refractive index among the insulating compounds represented by SiO ₂ , TiO ₂ and Al ₂ O ₃ . Semiconductor laser diode. The method according to claim 1 to 6, Wherein the lower distributed Bragg reflector, the resonator, and the upper distributed Bragg reflector are formed in a cylindrical or polygonal shape having a large diameter in the order of the lower distributed Bragg reflector, the resonator, and the upper distributed Bragg reflector, respectively. The method of claim 7, wherein The conduction channel layer is a short wavelength surface-emitting semiconductor laser diode, characterized in that formed in the range of 10 ~ 200㎛. The method of claim 1, And the conduction channel layer is formed only on the resonator. The method of claim 1, And the reflectance of the lower distributed Bragg reflector is greater than that of the upper distributed Bragg reflector so that a laser beam is emitted from the upper distributed Bragg reflector. The method of claim 1, And the reflectance of the upper distributed Bragg reflector is greater than that of the lower distributed Bragg reflector such that a laser beam is emitted from the lower distributed Bragg reflector. (A) The preliminary lower distributed Bragg reflector, the preliminary resonator layer, and the preliminary upper distributed Bragg reflector layer are sequentially grown on the semiconductor substrate, and then the preliminary upper distributed Bragg reflector layer is etched in a cylindrical shape by the first dry etching method. Forming a; (B) etching the preliminary resonator layer into a cylindrical shape having a diameter larger than that of the upper dispersed Bragg reflector by a second dry etching method to form a resonator layer; (C) etching the preliminary lower distributed Bragg reflector layer into a cylindrical shape having a diameter larger than that of the resonator layer by a third dry etching method to form a lower distributed Bragg reflector; And (D) forming a current confined layer made of an air layer on the outer side of the energized channel layer by removing the energized channel layer included in the resonator layer by etching it from a side; Method for producing a short-wavelength surface-emitting semiconductor laser diode comprising a. The method of claim 12, In the above step (a), the preliminary lower and upper dispersed Bragg reflector layers are each repeatedly stacked a plurality of GaN layers having a relatively high refractive index and an AlGaN layer having a relatively small refractive index, or Al _y Ga _1-y having a relatively large refractive index. It is formed by repeatedly stacking an N layer and an Al _x Ga _1-x N layer having a relatively low refractive index a plurality of times, and the preliminary resonator layer is an n-Al _x Ga _1-x N lower carrier limiting layer, In _x Ga _1- Fabrication of a short wavelength surface emitting semiconductor laser diode formed by sequentially stacking an active layer of _x N, a p-Al _x Ga _1-x N upper carrier limiting layer and an AlN or Al _x Ga _1-x N conducting channel layer Way. The method of claim 13, In the preliminary resonator layer, the AlN or Al _x Ga _1-x N conduction channel layer is laminated in advance of the n-Al _x Ga _1-x N lower carrier limiting layer or the n-Al _x Ga _1-x N lower carrier limiting layer. A method for manufacturing a short-wavelength surface emitting semiconductor laser diode, which is stacked before the p-Al _x Ga _1-x N upper carrier limiting layer. The method according to claim 13 or 14, In the step (a), when the wavelength of the generated light is λ and the refractive index of the constituent material of the Bragg reflector layer is n, the stacks of the upper and lower dispersed Bragg reflector layers are alternately stacked by λ / 4n thickness, respectively. A method for producing a single mode GaN based surface emitting laser diode. The method according to claim 13 or 14, To prevent the AlN or Al _x Ga _1-x N conduction channel layer from being etched at the same rate as the GaN or Al _y Ga _1-y N low refractive index layers of the upper and lower dispersed Bragg reflectors in step (d). In the step (a), the GaN or Al _y Ga _1-y N high refractive index layers of the upper and lower dispersed Bragg reflectors are formed such that the molar ratio of Al is smaller than that of the AlN or Al _x Ga _1-x N conduction channel layer. A method for producing a short wavelength surface-emitting semiconductor laser diode, characterized in that. The method according to claim 13 or 14, The preliminary resonator layer is formed to have a thickness of mλ as a whole when a wavelength of light generated is λ and an arbitrary integer m. The method of claim 12, The (a) step in the _{n-Al x Ga 1-x} N carrier trapping layer of the bottom and the _{p-Al x Ga 1-x} N n-GaN contact layer for each metal contact on top of the carrier trapping layer and the p- The sub-step of forming a GaN contact layer; The method of manufacturing a short-wavelength surface-emitting semiconductor laser diode further comprising. The method of claim 18, And (d) depositing a metal for electrode on the upper edges of the n-GaN contact layer and the p-GaN contact layer, respectively, after the step (d). The method of claim 12, The step (d) is a method for manufacturing a short wavelength surface-emitting semiconductor laser diode, characterized in that by the wet etching method. The method of claim 12, In the step (a), the upper dispersed Bragg reflector layer and the lower dispersed Bragg reflector layer are formed by stacking a plurality of pairs of materials having a large difference in refractive index among the insulating compounds represented by SiO ₂ , TiO _2, and Al ₂ O ₃ . A method for producing a short wavelength surface-emitting semiconductor laser diode, characterized in that.