JPS62137879A - Junction type semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To use the specified light in the vertical direction absorbing said light effectively by a method wherein a P-N junction only actually extending in vertical direction to a flat plate part is formed. CONSTITUTION:A heterowafer comprising an N-type AlxGa1-xAs layer A epitaxially grown to form a columnar protrusion P and an upper layer B1 is produced on an N-type GaAs substrate B3 and then said N-type AlGaAs layer A is ion-etched to form the columnar protrusion P. Next, with a masking layer 1 left as it is, another masking layer 2 is formed using the known masking agent of masking layer 1 on the surface of said columnar protrusion P and the upper layer B1. At this time, if the side periphery of columnar protrusion P is not in a state of no-masking, said periphery is formed into the state of no-masking by soft-etching process and then zinc is diffused in the impurity-fit P-type regions to form a P<+> type region R1 and P-type region R2 so that a cylindrical P-N junction PN1 only may be formed on the interface between a no-impurity region and the P-type region R2.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a semiconductor light emitting device that can be used as a light emitting diode or a semiconductor laser, and in particular, to a semiconductor light emitting device that can be used as a light emitting diode or a semiconductor laser. The present invention relates to a junction type semiconductor light emitting device in which a pn junction is formed in a direction perpendicular to a substrate without substantially forming a pn junction and efficiently emits light.

(Prior art) A light emitting element that emits light in a direction perpendicular to a substrate can be easily coupled with an optical fiber, and can also be used as a surface emitter to form a one-dimensional or two-dimensional array structure.
A: Since they are expected to be used in various applications such as information equipment, development has been progressing in the research field of semiconductor lasers and light emitting diodes, and in recent years, a wide variety of products have been put into practical use.

For example, Electronics Letters by Ito et al.
1984, vol. 20, No. 14, No. 577~
On page 579, a pn junction perpendicular to the substrate extending within a columnar projection formed perpendicular to the base is used as a light emitting portion, and this light emitting portion directs light from the tip of the columnar projection perpendicular to the substrate. A light emitting device using a compound semiconductor light emitting element that emits light is disclosed.

As shown in FIG. 3, one basic structural example of a conventional vertical light-emitting type semiconductor device is as follows: A columnar projection (P) consisting of an n-side electrode (El) provided on the side peripheral surface and the upper surface of the flat plate portion (B), and an n-side electrode (B2) provided on the lower surface of the flat plate portion (B). Inside, there is a pn junction PNI extending perpendicularly to the flat plate part (B), and also in the flat plate part CB).
There is a pn extending in a direction parallel to the flat plate part (B).
Junction PN2 is present.

The flat plate part (B) includes an n-type GaAs substrate (B3), an n-type AI GaAs layer (B2) which is a barrier layer, and an n-type GaAs substrate (B3).
s[(B1), and the columnar projections (P) are n-type GaA
It is made of the same material as s1i (B1). In the flat plate part (B) and in the columnar projection (P), p9 type GaAs or A12 is formed by thermal diffusion of impurities (e.g. zinc).
GaAs region (R1) and p-type GaAs or AIG
There is an aAs region (R2), which forms a columnar process (P
), there is a cylindrical pn junction PNI at the boundary between the region (R2) and the region (R2) where impurities are not diffused, and there is also a flat plate portion (B
In the barrier layer (B2) of ), a pn junction PN2 is formed at the interface between the region (R2) and the region where impurities are not diffused.

Then, a current is passed between the electrodes (El) and (B2), and light is emitted upward from the tip of the columnar projection (P).

[Problem that the invention seeks to solve]

In a semiconductor light emitting device with such a structure, an electrode (lit),
When a current is passed between (B2), the current not only flows through the circuit C1 that passes through the pn junction PNI, but also flows into the circuit C2 that passes through the pn junction PN2.

By the way, the purpose of such a semiconductor light emitting device is to emit light in a direction perpendicular to the flat plate part, and of the above two types of pn junctions, pnn junction PN1 causes vertical light emission, and pn junction PN2 causes horizontal light emission. , pn junction PNI is useful, pn junction PN2 is inherently abhorrent.

Therefore, in order to reduce the current flowing through the circuit C2, n
type GaAs substrate (B3), A having a wider forbidden band width than the GaAs layer of the columnar protrusion (P) having a pn junction PNI is formed.
The AI GaAs layer (B2) is epitaxially grown to a thickness of 10 to 20 μm, and the AI GaAs layer (B2) is used as a current blocking layer, and a pn junction PN2 is provided within this AI GaAs current blocking layer. The current flowing through the circuit C2 is not negligibly small, and as a result, the pn junction PN2 contributes to light emission, and the efficiency of current injection into the circuit C1 decreases. Also, n-type A
It is technically difficult to stack a thick I GaAs layer with uniform composition, good crystallinity, and an increase in cost.

Therefore, an object of the present invention is to emit light only in a direction substantially perpendicular to the substrate without having a thick semiconductor layer that acts as a current blocking layer with a wider forbidden band width than the semiconductor layer constituting the columnar protrusion. The object of the present invention is to provide a low-cost semiconductor light-emitting device that is free from technical difficulties.

[Means for solving problems]

The purpose is to provide a flat plate portion, a columnar protrusion provided on one side of the flat plate portion, and a columnar protrusion provided at any location on the flat plate portion and the columnar protrusion.
i, which has a pn junction extending perpendicularly to the flat plate part in the columnar protrusion, and has substantially no pn junction extending parallel to the flat plate part in the flat plate part This is achieved by a type semiconductor light emitting device. Specifically, in the junction type semiconductor light emitting device of the present invention, for example, the top surface of the columnar projection and the surface of the flat plate portion are in a masked state, and the side peripheral surface of the columnar projection is in an unmasked state to diffuse impurities, pn extending substantially perpendicularly to the flat plate portion within the columnar projection;
It is formed by forming only a bond.

[Effect]

Since the junction type semiconductor light emitting device of the present invention has only the pn junction PNI extending substantially perpendicularly to the flat plate portion, it emits light only in the vertical direction.

〔Example〕

Embodiments of the junction type semiconductor light emitting device of the present invention will be described below based on the drawings.

Basically, the light emitting device of the present invention, as shown in FIG.
A flat plate part (B), a cylindrical projection (P) provided on one side of the flat plate part (B), and a cylindrical projection (P) provided on the side peripheral surface of the cylindrical projection (P) and the top surface of the mokari part (B). The p-side electrode (El) and the flat plate part (
B) n-side electrode (B2) provided on the lower surface and flat plate part (B)
An insulating film (2) interposed between the upper surface of the
). Inside the cylindrical projection CP), there are a p type region R1), a p type region (R2), and a flat plate part (B).
A cylindrical pn junction PNI extending perpendicularly to the flat plate part (B) is formed in the flat plate part (B).
) is not formed.

The light emitting device of this example has only a pn junction PNI and pn
Since the structure does not have a junction PN2, the electrodes (El), (B
2) When a current is injected between them, the pn junction PNI emits light only in the direction substantially perpendicular to the flat plate portion (B).

Furthermore, current flows from the side peripheral surface of the cylindrical protrusion (P) to the circuit C1 that passes through the pn junction PNI, but since the current does not flow to parts other than the circuit CI due to the insulating film (2), the current flows to the light emitting part. The injection efficiency will be improved, resulting in increased light output.

In addition, there is no need to grow a current blocking layer on the substrate (B3), and only the layer for forming the cylindrical protrusion (■) made of the material selected according to the required emission wavelength is grown on the substrate. It is sufficient to grow epitaxial cells on (B3), or it is also possible to form columnar protrusions (P) from the substrate itself without an epitaxial growth layer, so that manufacturing costs can be reduced.

In the above embodiment, it is also possible to have a structure in which the part of the lower surface of the substrate (B3) that is directly under the cylindrical projection (P) is shaved off in the direction of the cylindrical projection (P), and in this case, the circuit C
1 becomes shorter, the current injection efficiency can be further improved.

Next, an example of a method for manufacturing a light emitting element having the structure shown in FIG. 1 will be described using a GaAs substrate and A7! A case where GaAs is grown epitaxially to obtain light emission with a wavelength of ^l will be described.

First, a cylindrical protrusion (P
) and n-type AlxG for forming the upper layer (B1).
A heterowafer on which an a+-XAs layer (A) is epitaxially grown is manufactured (see FIG. 2C). The thickness of the upper epitaxial growth layer (A) is, for example, 2 to 200 layers. For this hetero wafer, the above n-type AβGaAsJl (A
) is ion-etched to form a cylindrical protrusion (P) (see Figure 2). The remaining portion of the upper Ji (A) from which the cylindrical projection (P) is cut out becomes the upper layer (B1). This upper layer (B1) is not necessarily essential (the substrate (B3)
) The cylindrical protrusion (P) may be cut out until the cylindrical protrusion (P) has a mask layer (1) applied during the above etching process on the top surface of the cylindrical protrusion (P). However, the cylindrical protrusion (P
) and the surface of the upper layer (B1) are coated with a mask layer using a known masking agent (for example, silicon nitride, silicon oxide, etc., which can be applied by electron beam deposition, sputtering, CVD, etc.). (2) shall be provided. At this time, if the side peripheral surface of the cylindrical protrusion (P) does not become unmasked, soft etching is performed using a normal method to unmask it, and then the p-type impurity (preferably zinc) is diffused. to form a p-type region R1) and a p-type region (R2) shown in FIG. 1(b) in the cylindrical projection (P),
As a result, the region where impurities are not diffused and the region (R2)
Only a cylindrical pn junction PNI is formed at the interface with (see FIG. 2C).

After the diffusion process, an electrode (El) made of, for example, Cr-Au is placed as a p-side electrode material on the side peripheral surface and top surface of the cylindrical projection (P) and the top surface of the upper IS (Bl), and an electrode (El) made of, for example, Cr-Au is placed on the side circumferential surface and top surface of the cylindrical projection (P) and on the upper surface of the upper IS (Bl).
3) An electrode (B2) made of, for example, Au-Ge is provided as an n-side electrode material on the lower surface by means such as vacuum deposition (see FIG. 2C). Here, the electrode (El) is connected to the upper layer (B1
) is convenient because wire bonding can be easily performed using the electrode (El) on the upper surface of the sublayer (81) as fII in subsequent steps. Thereafter, by removing unnecessary electrode materials and mask layers by a lift-off method (see Figure 2C), the cylindrical protrusion (P) is formed in a direction perpendicular to the substrate (B3) as shown in Figure 1. has only a pn junction PNI extending to the flat plate part (B)
A junction type semiconductor light emitting device is manufactured that can be used as a light emitting diode without having a pn junction pH2 within it.

During the lift-off process, the p-side electrode (El) and the mask layer (2) on the upper surface of the flat plate part (B) may be removed (second
(see Figure g). In this case, the electrode (El) has a cylindrical projection (
Since it exists only on the side circumferential surface of P), let us assume that the upper layer (Bl)
Even if the mask layer (2) is not left as an insulating film on the upper surface of the circuit C1, the '@ current does not flow to any part other than the circuit C1.

Furthermore, in the obtained semiconductor light emitting device, the substrate (B3
A reflective mirror or reflective film is provided on the lower surface of the columnar projection (P) directly below the cylindrical projection (P), and a translucent reflective mirror or reflective film is coated on the top surface of the cylindrical projection (P) to prevent light. When equipped with a resonance mechanism, it can also be used as a semiconductor laser.

In this semiconductor laser, optical feedback occurs in the above-mentioned amplified spontaneous emission from the pn junction PNI, and laser oscillation occurs due to stimulated emission, and the strong and well-directed emitted light is transmitted to the above-mentioned translucent reflector. or the substrate (B) through the reflective film.
3) is emitted in a direction perpendicular to.

The light emitting device of the above embodiment has an epitaxial growth layer made of the same material as the substrate on the substrate, but in this case, the lattice constant of the substrate and the lattice constant of the epitaxial growth layer are necessarily the same. There is no need to intentionally provide an epitaxial growth layer on the substrate -F, and the substrate alone can be used as a light emitting element. However, the substrate is made by cutting an ingot with il
The crystals of the material constituting 1i are disordered, but the crystals of the epitaxial growth layer are orderly, so a light-emitting element provided with an epitaxial growth layer can emit more powerful light. When epitaxially growing a material that has a lattice constant different from that of the substrate, the material is usually epitaxially grown directly on the substrate.
It is necessary to provide a gradient layer between the substrate and the epitaxially grown layer without providing i. A graded layer is created by first growing a layer with the same lattice constant as that of the substrate on a substrate using another material, then sequentially growing layers with gradually changing lattice constants on top of that layer. A layer with the same lattice constant as that of the epitaxially grown layer that is the light emitting layer is grown. As an example of this, when growing fnGaP, a light emitting material, epitaxially on a GaAs5 plate,
A graded layer made of GaAsyP+□ is provided. That is,
The lattice constant of GaAs and the 1nGaP
The difference between the lattice constant and the lattice constant can be alleviated. Here, the top layer of the gradient layer (lattice constant of lnGaP and GaAsyP+
It is more preferable to grow a slightly thicker layer (with the same lattice constant of □) and use it as a buffer layer.

In the present invention, the electrodes (El) and (E2) are not limited to the positions and sizes shown in the examples, but are provided at any position and with any size as long as the purpose of the present invention can be achieved. be able to. Further, there are no particular restrictions on the method of forming the pn junction, such as impurity diffusion method,
The epitaxial vapor phase growth method of p (or n) type semiconductor layer and n (or p) type semiconductor layer (in this case, heterojunction is also possible) or other methods may be used.

In the present invention, a pn junction PNI that contributes to vertical light emission is used.
The length of can be increased by increasing the height of the columnar projection (P), so the height of the columnar projection (P) is preferably at least 2N-1, particularly at least 10u. It is possible to form columnar protrusions (P) on the surface of a semiconductor wafer, for example, by a reactive ion etching jig method, and the method of the present invention having columnar protrusions (P) with a height of several tens to hundreds of units. A light emitting device can be easily manufactured.

Regarding the present invention, the "vertical direction" in the columnar projection (P)
There is no need to limit the meaning of ``to'' to mean only a direction perpendicular to the flat plate part (B) at an angle of 90 degrees, and it also includes cases where the angle of inclination is slightly larger or smaller than 90 degrees with respect to the substrate. For example, the entire columnar protrusion CP) or only the coaxial cylindrical pn junction PNI formed inside it may be formed into a truncated conical shape with a larger diameter at the bottom to make it easier to connect to the optical fiber. It is also possible to focus the output light on a truncated cone, or conversely,
Depending on the purpose of use, the light may be dispersed appropriately.

The light emitting material used in the junction type semiconductor light emitting device of the present invention includes GaAs, Gar' which is an m-v group compound semiconductor.
, 8/GaAs, InP% 1nGaAs
P, 1nGaP, 1nAIP.

GaAsP, GaN, 1nAsP, In
Zn5e, which is a II-Vl group compound semiconductor such as AsSb
,, ZnS, ZnO, CdSe, CdTe, etc.
rV-Vl group compound semiconductors PbTe, Pb5n
There are Te, Pb5nSe, etc., as well as SiC, which is an N-IV group compound semiconductor, and it is possible to apply them by taking advantage of the advantages of each lumber-1.

〔Effect of the invention〕

As is clear from the above, the junction type semiconductor light emitting device of the present invention has pn
By having only the junction PNI, it is possible to effectively obtain light in the vertical direction, and it is possible to effectively utilize the desired light in the vertical direction. The light-emitting device of the present invention uses the amplification effect by stimulated emission to obtain more powerful vertical output light, and can be used in light-emitting diodes, semiconductor lasers, super luminescence diodes, high-output light-emitting diodes, etc. can be realized.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are cross-sectional views of the first embodiment of the junction type semiconductor light emitting device of the present invention, and FIGS. 2(, 3) to (f) are cross-sectional views of the light emitting device shown in FIG. FIG. 2(g) is a flowchart showing an example of the manufacturing process, FIG. 2(g) is a diagram showing a modification of the light emitting device manufactured by the process, and FIG. 3 is a sectional view of a conventionally known junction type semiconductor light emitting device. (B) Two-hand plate part (P) Two cylindrical projections (El), (B2): Electrodes (C1), (C2): Circuit (PN 1), (Pl+ 1.): I) N-junction (81): upper layer

Claims (3)

[Claims] (1) Consists of a flat plate part, a columnar protrusion provided on one side of the flat plate part, and an electrode provided at any location on the flat plate part and the columnar protrusion, extending in the direction perpendicular to the flat plate part within the columnar protrusion. A junction type semiconductor light emitting device having a pn junction located in the flat plate portion and having substantially no pn junction extending in a direction parallel to the flat plate portion within the flat plate portion. (2) Diffusion of impurities is carried out with the top surface of the columnar protrusion and the surface of the flat plate part in a masked state, and the side peripheral surface of the columnar protrusion in an unmasked state, so that the impurity is diffused into the columnar protrusion substantially on the flat plate part. A junction type semiconductor light emitting device according to claim 1, wherein only a pn junction extending in the vertical direction is formed. (3) Claim No. 1 in which the columnar projections are formed from an epitaxial growth layer provided on one side of the flat plate portion.
) The junction type semiconductor light emitting device described in item 2.