JPH0525189B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a monolithic light emitting diode array having a common electrode on the back side of a semiconductor chip and a plurality of individual electrodes on the front side.

[Conventional technology] Conventionally, monolithic light emitting diodes are
A structure in which impurities are diffused into an epitaxial growth layer grown on a single crystal substrate is known.

FIG. 3 is a top view of a conventional monolithic light emitting diode array, and FIG. 4 is a top view of a conventional monolithic light emitting diode array.
FIG. 3 is a perspective view of section A′.

In the figure, 1 is an n-type GaAs substrate, 2 and 3 are an epitaxially grown n-type GaAs _1-x P _x layer and an n-type GaAs layer, respectively. 4 and 5 are n-type
A p-type region formed by selectively diffusing Zn from the surface of the GaAs layer 3, 4 is a light emitting recombination part, and 5 is an isolation region of each light emitting diode section consisting of each light emitting recombination part 4. It's a tribe. 6 is the n-type GaAs layer 3 of each light emitting diode part
An individual positive electrode for conducting electricity is provided on the electrode portion 9, and 7 is a negative electrode common to each light emitting diode portion provided on the back surface of the n-type GaAs substrate.

When a positive bias is applied between the positive electrode 6 and the negative electrode 7, the electrons from the n-type GaAs _1-x P _x layer 2 become p
The light is injected into the luminescent recombination part 4 which is the mold region, and the light due to the luminescent recombination is transferred to the individual positive electrode 6 and the n-type
The light is emitted to the outside as indicated by arrow C through the light extraction hole 8 provided in the GaAs layer 3.

[Problems to be Solved by the Invention] However, because the conventional diffused light emitting diode array has the above-mentioned configuration, the problem is that the light emitting area is small compared to the pn junction area, and the amount of light emitted relative to the current is small. It was hot.

In order to solve this problem, it is easy to think of enlarging the light extraction hole 8, but in order to do so, the outline part of the electrode 6 that forms the light extraction hole 8 becomes thinner, and if that part becomes disconnected, etc. However, a new problem arises in that the amount of light emitted relative to the current decreases significantly.

[Object of the Invention] An object of the present invention is to solve the problems of the prior art described above and to provide a monolithic light emitting diode array in which the light emitting diode portion has a large light emitting area and high light emitting efficiency.

[Means for solving the problem] That is, the gist of the present invention is to
At least one mixed crystal epitaxial layer is grown to form a junction surface, and the pn junction surface is divided into a plurality of island-like light emitting diode portions aligned in a row by mutually orthogonal mesa etching grooves. In the monolithic light-emitting diode array, a current-carrying wiring is drawn out from the center of the light-emitting diode part to an electrode region formed in a position parallel to the light-emitting diode part, and the light-emitting surface of each light-emitting diode part is The reason is that it is U-shaped.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a top view of the mesa-type monolithic light emitting diode array of the present invention, and FIG.
A perspective view of the B′ section is shown.

In the figure, 21 is a P-type GaAs substrate, 22 is an epitaxially grown p-type Ga _1-x Al _x As layer, and the value of the mixed crystal ratio x is within the range of x = 0.10 to 0.35. is appropriately determined depending on the desired emission wavelength. 23 is an n-type Ga1 _- yAlyAs layer epitaxially grown on the p-type Ga1- _xAlxAs layer 22;
By making this mixed crystal ratio y higher than the above-mentioned mixed crystal ratio x, the light transmittance for the emission wavelength from the p-type Ga _{1- x Al y} As
Increased injection efficiency of electrons from layer 23 and p-type
It is intended to confine the minority carriers injected into the Ga _1-x Al _x As layer 22.

Reference numeral 36 denotes a current supply wiring connected to the electrode portion 29 of the n-type Ga _1-y Al _y As 23 and led out to the individual negative electrode 26 . In addition, energizing wiring 3
6 and the individual negative electrode 26 are formed of a vapor-deposited metal film.

The electrode section 29 is located at the center of the light emitting diode section 30, and is designed to minimize the area occupied by the current-carrying wiring on the light emitting diode 30. Therefore, the light emitting area of the light emitting diode section 30 is large, and the shape of the light emitting surface is U-shaped.

Reference numeral 24 denotes a phosphosilicate glass (PSG) film provided to insulate the individual negative electrodes 26 from the n-type Ga _1-y Al _y As layer 23 other than the electrode section 29 .

25 is a mesa etching groove, 25a is an etching groove in the reverse mesa direction, and 25b is an etching groove in the forward mesa direction.
Provided to isolate 0. Note that etching grooves in the reverse mesa direction must be provided between adjacent light emitting diode sections 30, and etching grooves in the forward mesa direction must be provided so as to traverse the device.

Therefore, each individual negative electrode 26 is connected to the electrode section 2.
Since the wire is drawn out from 9 through the etched groove 25b in the forward mesa direction, there is no chance of breakage or disconnection at the edge of the mesa.

A common positive electrode 27 is formed by depositing a metal film over the entire surface of the p-type GaAs substrate 21.

In this structure, if a voltage is applied between the individual negative electrodes 26 and the common positive electrode 27 to cause a forward current to flow through the light emitting diode section 30, an n-type
Electrons are injected from the Ga _1-y Al _y As layer 23 into the p-type Ga _1-x Al _x As layer 22 to cause radiative recombination, and light is emitted upward from the mesa portion, that is, the U-shaped light emitting surface. .

Note that the individual negative electrode 26 is connected to the L
The reason for the shape is to facilitate wire bonding.

Example 1 A carrier concentration of 5× was deposited on the (100) surface of a 350 μm thick P-type GaAs substrate doped with Zn and having a carrier concentration of 2×10 ¹⁸ cm ^-3 by liquid phase epitaxial growth.
A p-type Ga _0.9 Al _0.1 As layer of 10 ¹⁶ cm ^-3 with a thickness of 20 μm and an n-type Ga _0.7 Al _0.3 As layer with a carrier concentration of 2×10 ¹⁷ cm ^-3
It was grown sequentially to 3 μm.

This surface is mesa-etched to provide two etched grooves in the <011> direction, which is the forward mesa direction, with respect to the (100) plane, and in the <011> direction, which is the reverse mesa direction perpendicular to the <011> direction. An etched groove was provided between the two forward mesa etched grooves. Then,
These mesa-etched grooves form light emitting diode portions aligned in a row in the <011> direction. The depth of each mesa etching groove is 5 μm, and the width of the light emitting part is 45 μm x 70 μm.
And so.

Next, a PSG film was grown to a thickness of 0.2 μm to cover the entire surface, and then the PSG film on the central portion of each light emitting diode portion, that is, the electrode portion, was removed using hydrofluoric acid in an area of 5 μm×10 μm.

Gold-germanium alloy/nickel/gold metal is placed on the PSG film on both sides of the light-emitting diode section so that it can be drawn out from the electrode section of each light-emitting diode section through the etched groove in the forward mesa direction to the individual negative electrode as a conductive wiring. The films were deposited to a thickness of 0.1 μm/0.2 μm/0.5 μm, respectively.

A gold-zinc/nickel/gold metal film having a thickness of 0.1 μm, 0.2 μm, and 0.5 μm, respectively, was deposited as a common positive electrode on the entire back surface of the substrate. The light-emitting surface is U-shaped, and the area in which light emission is suppressed by the current-carrying metal wiring is 10 μm x 30 μm, making the light-emitting area three times that of conventional devices.

The light emitting diode sections were formed at a rate of 16 per mm, and 128 light emitting diode sections could be formed in a chip of 1.6 mm x 8 mm.

The rise voltage of this mesa-type monolithic light emitting diode array is 1.5V, and the forward voltage is 2.0V.
10mA or more, reverse breakdown voltage is 7V or more, emission wavelength is 800mm
It was hot.

In addition, since the metal film is deposited on the etching in the forward mesa direction, no breakage occurs, and it is possible to obtain a mesa-type monolithic light emitting diode that does not break even after 2000 hours of use with a yield of 100%. Ta.

As described above, in the embodiment of the present invention, the light emitting area can be increased compared to the conventional technology,
Moreover, the light emitting efficiency can be increased, and furthermore, there is little variation in the characteristics of each light emitting diode section 30.

In the above embodiment, p-type GaAs was used as the substrate crystal, but it is also possible to use n-type GaAs.
When type GaAs is used, the common electrode side may be used as a negative electrode, and the individual electrode side may be used as a positive electrode.

In addition, the mixed crystal system formed on the GaAs substrate is also
It is not limited to GaAlAs, and other mixed crystal systems may be used.

[Effects of the Invention] As explained above, the mesa-type monolithic light emitting diode array of the present invention can increase the amount of light emitted with respect to current by reducing the area of the current carrying wiring formed on the pn junction layer. In addition, the light emitting efficiency can be increased, and furthermore, there is a remarkable effect that the variation in the light emitting characteristics of each light emitting diode section can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a top view showing an embodiment of the present invention, FIG. 2 is a perspective view taken along the line B-B' in FIG. 1, FIG. 3 is a top view showing a conventional example, and FIG. It is a perspective view of the AA' cross section in FIG. 1...n-type GaAs substrate, 2...n-type GaAs _1-x P _x layer,
3...n-type GaAs layer, 4...luminescence recombination section, 5...isolation stripe, 6...individual positive electrode,
7... Common negative electrode, 8... Light extraction hole, 9,
29...electrode section, 21...p-type GaAs substrate, 22...p
Type Ga _1-x Al _x As layer, 23...n-type Ga _1-y Al _y As layer, 2
4...PSG film, 25...Mesa etching groove, 26
...Individual negative electrode, 27...Common positive electrode, 3
0...Light emitting diode section, 36...Wiring for energization.

Claims (1)

[Claims] 1. At least one mixed crystal epitaxial layer is grown on a GaAs substrate so as to form a p-n junction, and the p-n junction is formed into a plurality of islands aligned in a line by mesa-etched grooves orthogonal to each other. In a monolithic light emitting diode array divided into light emitting diode parts having a shape, a power supply wiring is drawn out from the center of the light emitting diode part to an electrode region formed in a position parallel to the light emitting diode part, and A monolithic light emitting diode array characterized in that the light emitting surface of each light emitting diode section is U-shaped.