JP2777442B2 - Light emitting diode array - Google Patents

Description

The present invention relates to a light emitting diode array suitable for high-density printing or display.

(B) Conventional technology Conventionally, a light emitting diode array used for an optical printer or a light emitting diode array used for a projection type display such as a head-up display has a plurality of printing regions corresponding to print dots or display dots on the surface of a compound semiconductor. In this case, an electrode was formed on the surface of the compound semiconductor in ohmic contact with the light emitting region via an insulating film.

In such a monolithic light emitting diode array, an insulating coating on a thin film is provided on the surface as disclosed in JP-A-61-3763 and JP-A-62-242558. This insulating film is used for selective diffusion of the light emitting area, for protecting the surface of the compound semiconductor, for preventing pinholes such as the insulating film, and for maintaining the hardness of the electrode base in wiring such as wire bonding. There are objects such as one for absorbing dripping and impact and one for adjusting the luminance of the light emitting region. In order to achieve these objects, a plurality of insulating films are often provided on the surface of the compound semiconductor.

(C) Problems to be Solved by the Invention However, when the dot interval becomes narrower or the dots become smaller and denser, the electrodes become thinner and easily broken, and furthermore, the outline of the dots becomes conspicuous and the dots become conspicuous. Optical crosstalk between them is likely to occur.

As a result of examining this situation, these problems will become more noticeable at resolutions of 400 dpi (400 dots per inch) or more. This is because the step from the surface of the insulating film to the surface of the compound semiconductor becomes large, and the unclear contour and crosstalk of light are caused by the fact that the insulating film becomes a light propagation body (light pipe), and the amount of light propagation is It was found that the number increased when there was a lamination interface, and that light diffusion was significantly conspicuous.

(D) Means for Solving the Problems The present invention has been made in view of the above points, and has the following features: a first insulating film covering a periphery of a light emitting region; It has a laminated structure of a second insulating film provided on the surface and an electrode provided in ohmic contact with each of the light emitting regions and extending up to the second insulating film.

(E) Action Since the electrode gradually approaches the compound semiconductor from the surface of the insulating film, the step is small, and there is no interface of the insulating film near each light-emitting region, especially at a position between the light-emitting regions. The amount is smaller.

(F) Embodiment An embodiment of the present invention will be described below with reference to the drawings, using a light emitting diode array of 850 dpi as an example.

Reference numeral 1 denotes a compound semiconductor made of GaP, GaAsP, GaAlAs, GaAs, or the like, and has a plurality of light emitting regions 11 arranged in one row or in a staggered plurality of rows on the surface thereof by a selective diffusion method or the like.
The light emitting region has, for example, a surface of 40 × 15 μm and a depth of 2 to 7 μm.
In the case of a two-row staggered arrangement as shown in the figure, the spacing between the rows is about 60.0 μm, and the spacing between the light emitting areas in the same row (that is, the arrangement pitch) is about 117.6 μm with respect to the center of the emission area 11.

Reference numerals ₂ and ₃ denote first and second insulating films made of Si ₃ N ₄ , SiO ₂ , Al ₂ O _3, etc., which are sequentially laminated on the surface of the compound semiconductor 1. Is 600 ~ 1500Å, 800 ~ 2000Å for pinhole countermeasure film and wiring reinforcement base film,
In the case of a light extraction / brightness adjustment film, a film having a thickness of about 900 to 3000 mm is used. This first insulating film 2 is a light emitting region
The second insulating film 3 is provided on the surface of the compound semiconductor 1 with a hole of 35 × 10 μm, for example, at a position corresponding to the light-emitting region so as to cover the periphery of the light-emitting region 11.
Is provided on the first insulating film 2 on the substrate surface except for the band-shaped portion A having a width of, for example, 100 μm.

4 is laminated on the insulating coatings 2 and 3 to form a light emitting region.
Electrode 11 in ohmic contact made of Al, Cr, etc. The electrode 4 is thinned to, for example, 6 μm in width in the vicinity of the light emitting region 11 so as not to hinder the formation of a predetermined shape and size as a dot shape, and is disposed so as to cross the center of the light emitting region. In the vicinity of the edge of the compound semiconductor 1, a wiring region (wire bond pad or bump pad) is formed, so that the width is set to 50 to 100 μm. Therefore, the width of the lead portion may be widened so as not to cause a short circuit accident with the adjacent wiring. If the thickness of the electrode 4 is too large, it is not preferable because the shoulder collapses or a shadow is cast on the image of the light emitting state of the light emitting region 11, and if the electrode 4 is too thin, disconnection easily occurs. It is preferred that If necessary, the electrode 4 may be provided with an insulating layer for buffering impact during wiring or a protective insulating layer above the electrode 4 except for the wiring portion.

Reference numeral 5 denotes a common electrode provided on the back surface of the compound semiconductor 1 and made of Au or the like. Such a common electrode is a compound semiconductor 1
Can also be provided on the surface side of.

(G) Effects of the Invention With the above-described configuration, the electrode has a stepwise lower surface of the insulating film and comes closer to the surface of the compound semiconductor. Since there is no interface between the insulating films at the positions between them, the amount of light propagation is reduced. For example, in the above-described example, the size of the emission state of the light-emitting region is 42 × 17 μm, which is only 1 μm larger on each side of the rectangular light-emitting region, and the outline is sharp, and the light crossing with the adjacent light-emitting region is further improved. No talk was observed on the printed or projected display.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a light emitting diode array according to an embodiment of the present invention (XX section in FIG. 2), and FIG. 2 is a plan view of a main part of the light emitting diode array. 1 ... Compound semiconductor, 11 ... Issue area, 2 ... First insulating coating, 3 ... Second insulating coating, 4 ... Electrode.

Claims (1)

(57) [Claims] A plurality of light-emitting regions arranged on the surface of the semiconductor substrate, a first insulating film covering the periphery of the light-emitting regions, and a plurality of light-emitting regions provided on the surface of the substrate except for a strip including the light-emitting regions. A light-emitting diode array comprising: a second insulating film; and an electrode provided in ohmic contact with each of the light-emitting regions and extending over the second insulating film.