JPH04237171A - Light emitting diode array - Google Patents

Abstract

PURPOSE:To enable a light emitting diode array which serves as a printing light source of an optical printer to efficiently emit light and to be restrained from emitting light in a lateral direction so as to enhance light in intensity by a method wherein even sideways light out of light equally emitted in all directions from a PN junction region is taken out. CONSTITUTION:An N-type GaAsP layer 11 is laminated on the upside of an N-type GaAs substrate 10, an island-like Zn diffusion region 15 is formed thereon, and a P-N junction is formed at an interface between the Zn diffusion region 15 and the N-type GaAsP layer 11. Thereafter, a surface processing region 18 is provided to the upside of the P-N junction region through anisotropic etching, i.e., a reactive ion etching method employing CC12F2 gas.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a light emitting diode array,
In particular, a plurality of light emitting diodes suitable for a printing light source for an optical printer used in the print head of an optical printer device,
A light emitting diode array that is closely arranged on the same substrate and processed around the light emitting area to efficiently extract light and limit lateral light emission, making it possible to increase density. Regarding.

0002

[Prior Art] Conventionally, a light emitting diode array in which a plurality of light emitting diodes are closely arranged on the same substrate has been able to process image information, etc. relatively easily by electrically controlling each light emitting diode. Because of its advantages, it is widely used and efforts are being made to improve it. Moreover, various applications are being considered by taking advantage of the above advantages.

[0003] For example, with the remarkable progress of the information society in recent years, not only has the amount of information increased, but the quality of the information handled has also changed, including not only textual information but also image information such as diagrams and photographs. It is changing. Therefore, in response to these recent trends, printer devices serving as information output devices are required to have even higher printing speeds and printing densities. A light emitting diode printer that uses the light emitting diode array as a light source is well known as a printer that meets this demand.

Light-emitting diode printers employ a method in which a solid-state high-density light-emitting diode array optical writing head is arranged along a photoreceptor drum, and an image is formed on the surface of the photoreceptor drum using a focusing rod lens array. I'm taking it. The electrostatic latent image is formed by selectively blinking each light emitting diode in accordance with an image signal. The light emitting diode array optical writing head is composed of a plurality of array chips (for example, from 35 array chips), and one array chip includes 64 to 256 light emitting diodes at a predetermined density (for example, 16 elements/mm).
) and are usually integrated.

[0005] In this manner, in the light emitting diode printer, each light emitting diode is electrically controlled and driven, so no mechanical operating section is required. That is, it does not require a space for light deflection and has no moving parts. Moreover, it is sufficient to use a simple equal-magnification array lens in the optical system. For this reason, light-emitting diode printers are also known as non-impact optical printers, and compared to laser printers, which require a mechanical mechanism such as a rotatable polygon mirror for beam scanning and a corresponding complicated optical system. In principle, it is extremely small and has the advantage of increasing reliability.

FIG. 2 shows such a conventional light emitting diode.
1 is a cross-sectional view showing a partial structure of a light emitting diode array used in a printer. In FIG. 2, a conventional light emitting diode array has an n-type GaAs substrate 10 and an n-type GaAs substrate 10.
AsP layer 11, positive electrode 12, and negative electrode 13
, a SiN film 14 , a Zn diffusion region 15 , and a SiON film 16 .

In the structure of the conventional light emitting diode array shown in FIG. 2, only two light emitting diodes are shown to simplify the explanation.

[0008]

[Problems to be Solved by the Invention] In each of the light emitting diodes constituting the light emitting diode array described above, the light emitting action is different from that of a surface emitting laser, and the light emitting action is at the boundary between the Zn diffusion region 15 and the n-type GaAsP layer 11. Emit light isodirectionally in the light emitting region (pn junction part). Therefore, the light output of such a conventional light emitting diode array is
When compared with the light output of a single light emitting diode, only about 1/4 of the light actually emitted is utilized for the intended printing. Therefore, with conventional light emitting diode arrays, it is difficult to increase the printing speed, and it is also difficult to increase the density due to the risk of crosstalk with adjacent elements due to lateral light from the light emitting area. there were.

The present invention has been made to solve the above-mentioned problems.
The purpose of this project is to create a light-emitting diode with a structure that efficiently extracts light emitted from electrons injected from the electrodes to the outside by processing the periphery of the joint (joint part), and also prevents crosstalk in the lateral direction.

0010

[Means for Solving the Problems] In order to achieve the above object, the light emitting diode array of the present invention is arranged between adjacent light emitting diodes, and extracts light emitted from the light emitting diodes in the direction of the adjacent light emitting diodes. It is characterized by having a reflecting means for reflecting in the direction.

[0011]

[Function] As described above, the light emitting diode array of the present invention has a reflection means disposed between adjacent light emitting diodes.
Of the light emitted isodirectionally from the light emitting diodes, the light emitted in the direction of the adjacent light emitting diodes is reflected in the light extraction direction, thereby preventing crosstalk between adjacent light emitting diodes and improving the efficiency of external extraction. be.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partial sectional view of a GaAsP light emitting diode array, which is an embodiment of the light emitting diode array of the present invention. In FIG. 1, the light emitting diode array of the present invention includes an n-type GaAs substrate 10, an n-type GaAsP layer 11, a positive electrode 12, a negative electrode 13, a SiN film 14, a Zn diffusion region 15, and a SiON film 16. , a surface processing area 17, and another surface processing area 18.

Next, a method of manufacturing this light emitting diode array will be explained. First, Si is 2×1018cm-3
An n-type GaAsP layer 11 is laminated to a thickness of approximately 50 micrometers by VPE on the upper surface of an n-type GaAs substrate 10 doped at a concentration of A Zn diffusion region 15 is formed to have a thickness of about 1.5 micrometers, and a pn junction, which is a light emitting region, is formed at the boundary between the Zn diffusion region 15 and the n-type GaAsP layer 11.

Using photolithography on the upper surface of the island-shaped pn junction region thus formed, first the surface processed region 17 and then the surface processed region 18 are etched by anisotropic etching using CCl2F2 gas. Process using ion etching. After that, the n-type GaAsP layer 11
evaporate Al by photolithography on the top surface of
A positive electrode 12 is formed and the entire wafer is heated to perform alloying. Furthermore, AuG is formed on the lower surface of the n-type GaAs substrate 10.
A negative electrode 13 is formed by depositing e/Ni/Au,
Alloying is performed by heating the entire wafer. Thereafter, a SiON film 16 is formed as a non-reflective coating on the vapor deposition surface, and a bonding pad is formed in a region a predetermined distance away from the light emitting element.

As explained above, in the light emitting diode array of the embodiment of the present invention, the Zn diffusion region 1 serving as the light emitting region
5 and the n-type GaAsP layer 11, the surface processed region 17, 1 also functions as a reflecting mirror.
Since the light is extracted upward by the light beam 8, the efficiency of extracting the light to the outside is improved. Further, since no light is radiated to adjacent elements in the lateral direction, the distance between the elements can be reduced, and the elements can be arranged in high density.

In the above embodiments, the composition and film thickness of the light emitting diode array were explained using GaAs, GaAsP, etc., but the invention is not limited thereto, and other semiconductor materials such as AlGaInP, GaInAs,
It is also possible to use AlGaAs or the like with a desired composition and film thickness.

Furthermore, although a Zn diffused type pn junction region was used in the above embodiment, the light emitting diode array of the present invention is not limited to the diffused type, but can be obtained by doping acceptor and donor impurities during epitaxial growth. A pn junction region can also be used.

Further, in the above embodiment, the VPE method was used as a method for laminating semiconductor layers on the substrate, but other methods such as LPE method, MBE method, MOCVD method, CBE method, etc. can also be used. Regarding the etching methods used for surface processing, in addition to reactive ion etching using CCl2 F2 gas, there are also sputter etching using He, Ar gas, etc., and reactive ion beam etching using gases such as Cl, BCl3, etc. It is also possible to use In addition to dry etching using gas, desired processing can be performed by etching using a mixed solution of hydrochloric acid, hydrogen peroxide, water, or the like.

[0019]

Effects of the Invention As explained above, according to the light emitting diode array of the present invention, the light emitting area (p
The structure around the n-junction (n-junction) is processed to efficiently extract light emitted by electrons injected from the electrode to the outside, and to prevent crosstalk in the lateral direction, so the injection current is the same as that of conventional models. However, it is possible to efficiently extract light with a higher external extraction efficiency than before, and since radiation of light in the lateral direction is restricted, it is possible to achieve higher density.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a GaAsP-based light emitting diode array, which is an embodiment of the light emitting diode array of the present invention.

FIG. 2 is a partial cross-sectional view of a light emitting diode array used in a conventional light emitting diode printer.

[Explanation of symbols]

10 N-type GaAs substrate 11 N-type GaAsP layer 12 Positive electrode 13 Negative electrode 14 SiN film 15 Zn diffusion region 16 SiON film 17, 18 Surface processing area

Claims (1)

[Claims] 1. A light emitting diode array for an optical printer, comprising a plurality of light emitting diodes arranged on the same substrate,
A light emitting diode array characterized by having a reflecting means disposed between adjacent light emitting diodes and reflecting light emitted from the light emitting diodes toward the adjacent light emitting diodes in a light extraction direction.