JPS6032373A - Lateral light emitting light emitting diode array structure - Google Patents

Abstract

PURPOSE:To eliminate a light leakage by forming light absorbing layers on the opposite side to the junction side, and forming a notch which extends to the opposite side surface to the junction side of the firset conductive type layer continued to a gap between the second conductive type layers. CONSTITUTION:High density Zn- and Ge-doped layers 6, 7 are formed on the surface of a P type layer 1 and an N type layer 2, and acted as a light absorbing layer. A plurality of fine slots 7 which exceed a P-N junction surface 3 are formed from the side of the layer 1, and the layer 1 is divided into a plurality of portions. Two ends perpendicularly crossing the slots 8 are cut substantially perpendicularly to the P-N junction surface 3 as light emitting surfaces 10a, 10b. A notch 9 which extends to the surface of the layer 2 is formed continuously to the fine slots 8 on the rear end 10b. Thus, an LED array 20 in which a plurality of layers 1 isolated via the slots 8 are aligned on the common layer 2 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an LED array structure in which a large number of light emitting diode (hereinafter referred to as rLEDJ) elements are arranged in one row, more specifically, P N 4'i = approximately The present invention relates to a lateral light extraction LED array structure in which light is extracted from a vertical plane.

The LED has a second conductivity type layer (P layer or NJi layer) formed on a first conductivity type layer (N/i! or P layer) to form a PN junction, and a forward direction ( When an electric current is applied, holes and electrons recombine near the PN junction surface either directly or through the impurity level 7, thereby producing light emission.As the first and second conductivity type layers, G
m-v group compound semiconductor crystals such as aP and 'GaAs, and n-Vl group compound semiconductor crystals such as CdTe are used. This LED is 4! It is widely used in practical applications such as r-type display.

On the other hand, recently, a printer using the above-mentioned LED as a writing light source has been proposed, and various studies have been conducted. This type of printer generally uses a large number of LED elements arranged in a row to emit light that sensitizes the material.
An array is used as a writing light source, and the array and photosensitive phase are moved relative to each other in a direction perpendicular to the element arrangement direction.

In the above-mentioned printers, it is desirable to arrange LED elements in high density in order to increase the resolution, and for this reason, the LED array is generally composed of LED elements with a PN junction formed therein.
This is obtained by carving a large number of parallel narrow grooves extending from the optical surface of the second conductivity type layer to the N junction surface in the D-type layer. That is, by providing a large number of narrow grooves as described above, the second conductivity type layer is divided into many parts on the common first conductivity type layer, thereby forming a large number of LED elements.

and I) perpendicular to the narrow groove including the N bonding surface]
The two end faces are cut approximately perpendicular to the PN junction surface to serve as the light extraction surface (front end surface), and the light emitted near the PN junction surface is directed laterally from this light extraction surface, that is, approximately parallel to the PN junction surface. It is designed to be taken out in a certain direction.

However, in the lateral light extraction LED array having a common first conductivity type layer as described above, certain LEDs
Many problems have been observed when photon emission leaks to the side of an adjacent LED element and is extracted from the light extraction surface of the adjacent LED element, causing so-called "optical crosstalk."

In other words, among the light emitted near the PNN junction, the light that is tilted toward the adjacent LED element enters the adjacent element within the common first conductivity type layer, and is first transmitted to the back surface of the first conductivity type. The light then reflects between the surfaces of both the second conductivity type layer and the first conductivity type layer, propagates toward the light extraction surface, and leaks from the light extraction surface of the adjacent element.

This type of light leakage occurs not only from light that travels directly from the light emitting part to the light extraction surface (but also from light that travels from the light emitting part to the rear end surface, is reflected at the rear end surface, and heads toward the light extraction surface). arise.

It is an object of the present invention to provide a lateral light extraction LED array structure that does not cause optical crosstalk as described above.

As described above, the lateral light extraction LED an-i structure of the present invention has a plurality of second conductivity type layers (P layer or N layer) in one row on a common first conductivity type layer (N layer or P layer bud). In an LED array structure in which a PN junction surface is formed by arranging the layers, a light absorption layer is provided on each of the surfaces of the first and second conductivity type layers opposite to the junction side, and a light absorption layer is provided on the side opposite to the front end surface. The device is characterized in that a notch is provided on a certain rear end surface so as to be continuous with the gap between the second conductivity type layers and extend to the surface opposite to the bonding side of the first conductivity type layers.

When the light absorption layer as described above is provided, light is transmitted to the surfaces of the first conductivity type layer and the second conductivity type layer (the surface opposite to the bonding side).

The same applies hereinafter), so that light is no longer reflected between the surfaces of both layers and then proceeds to the light extraction surface side. Furthermore, if the above-described notch is provided in the rear end surface of the array, the first conductivity type layer of each LED element is optically separated from each other in the vicinity of the rear end surface. The light that travels inside the conductivity type layer toward the rear end face is
It becomes difficult to penetrate into the first conductivity type layer of an adjacent element.

Embodiments of the present invention will be described in detail below with reference to the drawings. Here, an example will be described in which the first conductivity type layer is an N layer and the second conductivity type layer is a P layer, but of course, the structure and effects of the present invention will be the same as the following explanation even in the reverse case. Similarly, Figures 1A to 1G schematically illustrate the entire manufacturing procedure of an embodiment of the lateral light extraction LED array structure of the present invention. First, an indirect transition type LED wafer 10 such as a GaP LED wafer is prepared. This LED unit is composed of 8 layers 2 and a P layer provided on top of the 8 layers 2, and both layers form the entire PN junction surface 3 (Fig. 1A).
The P-side ohmic electrode 4 made of, for example, Au-Zn (10wt%) and the Au-Ge (12wL
%' ) / N-side ohmic electrode 5 made of Ni is formed by vapor deposition or the like (FIG. 1B), then P-side electrode 4,
Heat treatment is performed on the N-side electrode 5. For example, this heat treatment
1εD wafer 10 f l-I2 atmosphere 40
This is done by heating for 1 minute at a temperature between 0°C and 500"C. This heat treatment produces J, 2 layer 1 and 8 layer 2
Layers 6 and 7 doped with Zn and Ge at high concentrations are respectively formed on the surface of the substrate (FIG. 1C). This highly doped layer 6.7 acts as a light absorption layer that absorbs the principal metal. Note that such light absorption layers 6 and 7 are formed by depositing highly Zn-doped Ga on the surface of PNl, for example, before the electrodes 4 and 5 are vapor-deposited.
The P layer can also be formed by other methods, such as by fully laminating a Se-high-tope GaP layer on the surface of the 8-layer 2.

Next, a plurality of narrow grooves 8 are cut into the wafer 1° which has undergone the above processing from the 2 layer 1 side at least over the entire PN junction surface 3 using, for example, a gourd saw. By carving these narrow grooves 8, the two layers 1 are separated into a plurality of parts (Fig. 1D). After this, an etching process or the like is performed as appropriate to remove distortion caused by the grooving process. Next, the two end faces perpendicular to the narrow grooves 8 (that is, spread in the direction in which the narrow grooves 8 are lined up) are each cut approximately perpendicularly to the PN junction surface 3 to form a light extraction surface (front end face) ], Oa and the rear end surface 10b. On the rear end surface 101], a notch 9 that is continuous with the narrow groove 8 and extends to the surface of the 8 layer 2 is formed using, for example, a gouge 7 no gno (FIG. 1E).
. Thereafter, an etching process or the like is performed as appropriate to remove distortion caused by the cutting process.

In this way, an LED array 20 in which a plurality of P layers separated from each other by narrow grooves 8 are arranged side by side on a common N layer 2.
is obtained. This LED fixture 20 is firmly bonded onto the insulating substrate 1 and wired using wire bonding knobs (FIG. 11). Next, insulating light-shielding resin 1
2 is filled into the narrow grooves 8 and the notches 9 so as to completely cover the rear end surface 10b, and the light extraction surface 10a is polished (FIG. 1G).

The effects of the LED array 20 of this embodiment having the above structure will be described below. FIGS. 2 and 3 are a plan view and a side view schematically showing the LED array 20, respectively. In the LED element Ll consisting of eight common layers 2 and two individual layers 1, light 11 generated near the PN junction surface 3 is extracted laterally from the only light extraction surface 10a□ open to the outside.

If the light 12 that is emitted within the N layer 2 near the PN junction surface 3 of the LED element L] and propagates downward (to the surface side of the 8 layer 2) while tilting toward the adjacent L E I) element L2 side, if the light 12 7 is not formed, it is reflected on the surface of the N layer 20 and proceeds as shown by the virtual line g12, and the adjacent L E ]) element L
2] Although it leaks from Oa2, the light absorption layer 7
is formed, the light is absorbed by the light absorption layer 7 and does not leak out from the light extraction surface 10a2.

Furthermore, the light 13 that is emitted within the two layers 1 near the PN junction surface 3 of the LED element L1 and travels upward (toward the surface side of the two layers 1) from the adjacent LED element side 2 is emitted from the light absorption layer 6,
If 7 is not formed, it repeats reflection on the surface of layer 2 1 and layer 8 2 and progresses as shown in the virtual line 6+3,
Either the light leaks from the light extraction surface 10a2 of the adjacent LED element L2, or because the light absorption layer 6 is formed, it is absorbed by the light absorption layer 6 and does not leak from the light extraction surface 10a2.

Furthermore, light is emitted within the N layer 2 near the PN junction surface 3 of the L B D element L1, and the light is emitted downward (on the surface side of the 8th layer 2) and backward (on the rear end surface 101) by tilting toward the adjacent L E D element L2 side.
If the 8 layers 2 near the rear end surface]01] are completely common to each], EJ) element, the light 14 traveling toward the Go forward and adjacent L
E I) The light exits from the light extraction surface 10a2 of the element L2.However, as mentioned above, the rear end surface 10b has notches 9 that partially divide the N layer 2 in correspondence with each LED element.
is provided, this light 44 is reflected toward the center of L E D L+ on the side surface of the N layer 2 facing the notch 9, and is extracted from the light extraction surface 10a1 of the LED element L1.

In the above embodiment, the rear end surface 10 where the notch 9 is provided
Similar to the light extraction surface 10a, b is formed substantially perpendicular to the PN junction surface 3, but in the second embodiment shown in plan and side views in FIGS. 4 and 5, The rear end surface 110b is formed obliquely so that the angle formed with the PN junction surface 3 is an acute angle on the second layer 1 side (in addition, in FIGS. 4 and 5, the LBD array 20 of the first embodiment is Elements that are equivalent to the elements in are given the same numbers and their explanations are omitted).

Also in this LED array 120, since the light absorption layers 6, 7 and the notch 109 in the rear end surface 110b are provided, the effects described above can be obtained as is. In addition, the effects obtained by forming the rear end surface 110be obliquely will be explained below.

Light 1 that is emitted within the N layer 2 near the PN junction surface 3 of the LED element L1 and travels downward (to the surface side of the N layer 2) and backward (toward the rear end surface 110b side) on the side of the adjacent LED element element 2.
5, if the rear end surface 110b is not formed obliquely but is formed substantially perpendicular to the PN junction surface 3 like the light extraction surface 10a, the light will be reflected by the rear end surface 110b and displayed as a virtual line,
6+5, and leaks from the light extraction surface 1Oa2 of the adjacent LED element L2. However, the rear end surface 11
Since 0b is formed obliquely as described above, this light 15 is reflected at a sharper angle at the rear end surface 1], Ob, travels toward the light absorption layer 7, and is absorbed by the light absorption layer 7. Therefore, the light does not leak from the light extraction surface 10a2. In general, it is preferable that the rear end surface 110b is formed such that the angle it makes with the PN junction surface 3 is 45° to 85° on the two-layer 1 side.

In the LED array structure of the present invention, although it is not necessarily necessary to form the entire rear end surface of the array obliquely as described above, it is necessary to form the rear end surface obliquely as described above, since this further enhances the optical crosstalk prevention effect. Furthermore, although the aforementioned insulating light-shielding resin 12 is not necessarily required, by filling the entire thin groove 8 of such resin 12, it is possible to prevent light from flowing in a direction substantially perpendicular to the light extraction direction. Leakage can be reliably prevented.

The through hole explained in detail above, the lateral direction extraction LED of the present invention
The array structure completely prevents so-called optical crosstalk, in which the light emitted from the LED elements leaks from the light extraction surface of other elements, making it extremely suitable for the writing light source of the printer as described above. .

[Brief explanation of drawings]

Figures 1A to IG are explanatory diagrams illustrating the entire manufacturing procedure of an embodiment of the LED array of the present invention, and Figures 2 and 3 are a schematic plan view and a schematic diagram respectively showing the entire part of the LED array. Side View FIGS. 4 and 5 are a schematic plan view and a schematic side view, respectively, showing partially and completely schematically another embodiment of the LED array of the present invention. 1...P layer 2...Mountain l/N layer 3...
......PN junction surface 6.7...Light absorption layer 8...Narrow groove (gap) 9,109...Notch 10a...Light extraction surface (Front end surface) 10b, 110b... Rear end surface 20, 120...-L
ED array Figure 18 Old Figure 5' 1c cXUta ID @ Figure 1r IF (2)

Claims (1)

[Claims] A plurality of second conductivity type layers are arranged and bonded in a row on a common first conductivity type layer, and spread in the direction in which the second conductivity type layers are arranged, which is approximately perpendicular to the bonding surface of both layers. In the lateral light extraction LED array structure in which light emission is extracted from the front end surface, a source absorption layer is provided on each side opposite to the bonding side of the first and second conductivity type layers, and the front end surface is different from the original absorption layer. The lateral side is characterized by a notch being formed on the rear end surface on the opposite side, which extends continuously from the gap between the valleys of the second conductivity type layer to the surface opposite to the bonding side of the first conductivity type layer. Directional light extraction light emitting diode array structure.