JPH06268251A - Semiconductor light-emitting element and light-emitting device - Google Patents

Abstract

PURPOSE:To form semiconductor light-emitting elements, which are half as long in distance between light emitting points as conventional ones and easily aligned, on an amorphous substrate cheap and large in area. CONSTITUTION:A P-N junction is formed inside polycrystalline compound semiconductors 3 and 4 formed on both the sides of an amorphous substrate 1 through a crystal growth method. The semiconductors 3 and 4 are formed into LEDs 20 of mesa structure arranged in an array, and a current is injected into LEDs 20 of mesa structure to enable LEDs 20 on both the sides of a quartz glass substrate 1 to emit light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection type semiconductor light emitting device that can be used for LEDs used in printers, color displays, image sensors and the like.

[0002]

2. Description of the Related Art LED (L
ight Emitting Diode) is known. The LED forms a pn or pin junction of a compound semiconductor (GaAs, GaP, AlGaAs, etc.), applies a forward voltage to the junction, injects carriers into the junction, and utilizes the light emission phenomenon that occurs during the recombination process. It was done. Conventionally, such an LED has LPE made of a compound semiconductor such as GaAs, AlGaAs, InP, or InGaAsP, which is lattice-matched to each substrate, on a single crystal substrate such as GaAs or InP.
(liquid phase epitaxy) method, MOCVD (metal organic
chemical vapor deposition) method, VPE (vapor phase e
It has been manufactured by performing epitaxial growth using a crystal growth method such as a pitaxy) method and an MBE (molecular beam epitaxy) method and performing processing.

[0003]

[Problems to be Solved by the Invention] These GaAs and In
Since compound semiconductor substrates such as P are more expensive than Si or the like, the cost of devices manufactured on this substrate will be increased. Further, the compound semiconductor substrate is conventionally manufactured by the horizontal Bridgman method, the pulling method, or the like, but it is difficult to obtain a high-quality large-area substrate. For GaAs substrates, for example, wafers with diameters up to 3 inches are only commercially available. LED
LED array for printer and image sensor is 10c
A length of m or more is required. Therefore, by aligning and aligning fine chips (arrays), an array suitable for a required size has been manufactured. Each LED determines the dot spacing in the printer and the resolution in the image sensor.
The distance between them is generally equal to or larger than the diffusion length of carriers. If the bit-to-bit spacing is narrowed by using the microfabrication technique together, carriers will be diffused and it will be difficult to operate only the target LED bit.

A multi-color display using LEDs is manufactured by arranging light emitting diodes having different emission wavelengths. For example, it is manufactured by die-bonding a surface emitting type light emitting diode of two colors of red and green to a ceramic multilayer wiring board as a set. Therefore, an object of the present invention is to cut a large-area light emitting element array from a single substrate at a lower cost than a conventional compound semiconductor substrate,
Another object of the present invention is to provide a light emitting device that can be easily aligned.

[0005]

The above objects of the present invention can be achieved by the following constitutions. That is, the semiconductor material is a polycrystal or polycrystal film formed on both surfaces of a substrate in which epitaxial growth does not occur, and has at least a pn junction and a pin junction in each polycrystal or polycrystal film. , A p-type semiconductor and an n-type semiconductor, and a current is caused to flow between the electrodes to emit light at a pn junction and a pin junction. Here, the pn junction, the band gap of the semiconductor material forming the pin junction, or the light emitting mechanism may be different on both sides of the substrate, and the emission wavelength may be different between the light emitting elements provided on both sides of the substrate.

The above object of the present invention can also be achieved by the following configuration. That is, in the light emitting device, the semiconductor light emitting elements are arranged in parallel as a mesa structure, and the respective mesa structures are arranged so as to be offset from each other on both sides of the substrate.

A feature of the present invention is to form a polycrystalline semiconductor functioning as a light emitting element on a substrate on which epitaxial growth does not occur as described above. Here, the substrate on which epitacal growth does not have to be a single crystal, and may be made of an amorphous or polycrystalline inorganic material or metal material, or the substrate surface may be a polycrystalline, amorphous or single crystal inorganic material or metal. It is possible to use a material which is covered with a material. Therefore, since a material such as glass or ceramic can be used, a very wide range of device materials can be used.

The glass as the substrate is quartz glass,
For example, multi-component glass and crystallized glass can be used. Various oxide films such as SiO ₂ formed on various substrates by the CVD method, the sputtering method, the vapor deposition method or the like, a nitride film such as SiN, or a semitransparent metal thin film may be used. However, when the light is also extracted to the substrate side, the substrate must be transparent or semitransparent to the emitted light.

As the light emitting element, GaAs or AlG is used.
aAs, InP, InGaAsP, ZnS, ZnSe,
Various semiconductor materials having a pn junction or a pin junction such as CdTe can be used. Further, as a growth method of the light emitting element, MOCVD method, MBE method, VPE method, or the like can be used.

[0010]

In carrying out the present invention, the biggest problem is to prepare a polycrystalline film of large size grains on a substrate such as amorphous, ceramic, polycrystalline, etc. on which epitaxial growth does not occur. If a large grain can be formed, it can function as a semiconductor light emitting element. Amorphous, ceramic, or polycrystalline substrates, or single-crystal substrates whose crystal structure differs from the semiconductor material to be produced, or substrates with the same crystal structure but with a large difference in lattice constant, cover the entire surface of the substrate. Epitaxial growth of crystals does not occur. However, the microcrystals generated on the substrate at the initial stage of growth act as crystal nuclei, and the nuclei grow to form a polycrystalline film. If the size of each grain of the polycrystalline film is larger than the device size,
A device fabricated on the polycrystalline film will have characteristics similar to those of a single crystal device. Therefore, it becomes possible to supply the semiconductor light emitting device using a substrate which is cheaper than the conventional compound semiconductor substrate. Further, since a typical glass as an amorphous substrate has a large area and is easily available, the size of the device, which has been limited by the substrate size, can be significantly increased.

When forming a polycrystalline film on a polycrystalline substrate, the grain size is influenced by the grain size of the substrate, but MOC is formed on a quartz glass substrate which is an amorphous substrate.
Taking the case of forming a polycrystalline film by the VD method as an example, the size of the grains changes depending on the growth conditions. For example, grain growth temperature, grain growth pressure, growth rate,
The grain size can be controlled by controlling the feed rate of the raw material and the flow rate of the carrier gas. For example, the higher the growth temperature and the lower the growth pressure, the larger the grain size obtained. 850 under pressure of 10 Torr
In a preliminary experiment that tried to grow GaAs at ℃, the diameter was 30
A polycrystalline film composed of grains of μm or more was obtained.

As described above, by optimizing the conditions by, for example, the MOCVD method, it becomes possible to manufacture a polycrystalline film made of grains having a size larger than that obtained in the preliminary experiment. On this substrate, p-type and n-type AlGa
When As is grown, the p-type and n-type films become polycrystals having the same size as or larger than the polycrystal film which is the substrate. If the size corresponds to the size of the light emitting diode, characteristics that are not different from those of a single crystal device can be obtained. On the contrary, when the size of the grain is smaller than the size of the device, the grain boundary is not small in the device. At the boundary, carriers undergo non-radiative recombination. However, this does not mean that all of the carriers recombine non-radiatively,
Depending on the grain size, radiative recombination can be dominant. That is, although the performance is slightly inferior to that of the single crystal light emitting diode (LED), a light emitting diode (LED) that sufficiently functions can be obtained.

[0013]

Embodiments of the present invention will be described with reference to the drawings. Example 1 As an example for demonstrating the present invention, an example in which an AlGaAs light emitting diode is manufactured on a quartz glass substrate by MOCVD will be described below. FIG. 1 is a schematic view showing this manufacturing process. The quartz glass substrate 1 was used as a substrate, and etching with hydrofluoric acid was performed as a pretreatment. Further, in order to prevent abnormal generation of crystal nuclei due to impurities, the crystal nuclei were introduced into a MOCVD chamber and exposed to HCl at 1000 ° C. for 15 minutes to clean the surface. This 8
The temperature was lowered to 50 ° C., and the first growth was performed at a pressure of 10 Torr. Here, trimethylgallium as a Group 3 raw material,
Trithymel aluminum was used as the Group 5 raw material, arsine, and hydrogen was used as the carrier gas. Group 5 raw material /
The raw materials were supplied at a group 3 raw material ratio = 40 for 1 hour. As a result, on the quartz glass substrate 1, AlGaAs (x = 0.
4) Grain with a diameter of about 30 μm (not shown)
Grew up. Following this first growth, the p-type polycrystalline AlGaAs (x = 0.4) was formed at 800 ° C. under normal pressure.
Layer 3, n-type polycrystalline AlGaAs (x = 0.
4) Layer 4 was grown. This two-stage growth is for obtaining the p-type polycrystalline AlGaAs layer 3 or the n-type polycrystalline AlGaAs having good characteristics in the second growth. Then, the substrate 1 is turned upside down, and the polycrystalline AlGa is again subjected to the same steps.
As layers 3 and 4 were formed. The structure of the produced polycrystalline film is shown in FIG.

Next, a 70 μm □ mesa structure 5 was formed by chemical etching, and a p-type electrode 6 and an n-type electrode 7 were formed on the etched surface and the mesa structure 5, respectively (FIG. 1).
(B)). When the current-voltage characteristics of this element were measured,
Good rectification characteristics shown in FIG. 2 were obtained for the devices on both sides of the substrate. All the devices emitted light only when a forward bias was applied. FIG. 3 is an emission spectrum when a current of 10 mA is injected. Near 650 nm and 750 nm
Two peaks could be observed in the vicinity. The peak at 650 nm is due to the band edge of AlGaAs (x = 0.4), and the peak at 750 nm is due to the deep level.

FIG. 4 shows a light emitting device in which LEDs 20 made of a polycrystalline semiconductor are arrayed in mesa etching, and the mesa structures are alternately arranged on both sides of the quartz glass substrate 1. With such an arrangement, the distance between the light emitting points becomes half that of the conventional LED array. That is, when it is applied to an LED printer, the printable dot interval is half that of the conventional one.

Embodiment 2 Another embodiment of the present invention will be described with reference to FIG. A substrate in which a Cr film 10 was formed on both surfaces of the quartz glass substrate 1 by a sputtering method was used. This was heated to 800 ° C. in the MOCVD chamber and grown at a pressure of 10 Torr for 1 hour. Here, trimethylgallium, trithymel aluminum was used as the Group 3 raw material, arsine was used as the Group 5 raw material, and hydrogen was used as the carrier gas. Group 5 raw material / Group 3 raw material ratio = 4
The raw material was fed at 0 for 1 hour. As a result, the diameter 2 of AlGaAs (x = 0.45) is formed on the quartz glass substrate 1.
Grains (not shown) of about 0 μm were obtained. Following this first growth, the p-type polycrystalline AlGaAs (x = 0.45) layer 12, 850 ° C., at 800 ° C. under normal pressure.
Then, an n-type polycrystalline AlGaAs (x = 0.45) layer 13 was grown.

Then, the substrate 1 is turned over and the MOCV is performed again.
Polycrystalline AlGaAs layers 15 and 16 were formed by D. The structure of the produced polycrystalline film is shown in FIG. Then, the temperature is raised to 800 ° C. in the substrate chamber, and the raw material is supplied at a pressure of 10 Torr for 1 hour, so that AlGaAs (x = 0.
Grains (not shown) composed of 3) were grown. Then, the p-type polycrystalline AlGaAs is kept at 800 ° C. under normal pressure.
(X = 0.3) layer 15, n-type polycrystalline AlGa at 850 ° C.
An As (x = 0.3) layer 16 was grown. A part of the grown polycrystalline AlGaAs layers 12, 13, 15, 16 is etched with a sulfuric acid-based etching solution until reaching the Cr film 10, and n-type electrodes 17 are formed on the remaining polycrystalline AlGaAs layers 13, 16 respectively. (Fig. 5 (b)). On the other hand, Cr
The film 10 acts as an ohmic electrode of the p-type polycrystalline AlGaAs layers 12 and 15.

In this embodiment, the polycrystalline AlGaAs layer 12,
The band gap of the semiconductor material is different between 13 and the polycrystalline AlGaAs layers 15 and 16, and the emission wavelength is different between the light emitting elements provided on both sides of the substrate 1. Also in this embodiment, by arranging LEDs made of a polycrystalline semiconductor as in the case of the first embodiment shown in FIG. 4, the intervals of the light emitting points can be made half as compared with the conventional LED array.

Example 3 As an example for demonstrating the present invention, an example in which an AlGaAs light emitting diode is formed on a quartz glass substrate by MOCVD will be described below. FIG. 6 is a schematic view showing this manufacturing process. The quartz glass substrate 1 was used as a substrate, and etching with hydrofluoric acid was performed as a pretreatment. Further, in order to prevent abnormal generation of crystal nuclei due to impurities, the crystal nuclei were introduced into a MOCVD chamber and exposed to HCl at 1000 ° C. for 15 minutes to clean the surface. This 8
The temperature was lowered to 50 ° C., and the first growth was performed at a pressure of 10 Torr. Here, trimethylgallium as a Group 3 raw material,
Trithymel aluminum was used as the Group 5 raw material, arsine, and hydrogen was used as the carrier gas. Group 5 raw material /
The raw materials were supplied at a group 3 raw material ratio = 40 for 1 hour. As a result, on the quartz glass substrate 1, AlGaAs (x = 0.4
3) Grain with a diameter of about 30 μm (not shown)
Grew up. Subsequent to the first growth, the p-type polycrystalline AlGaAs (x = 0.4
3) Layer 3 and non-doped polycrystalline AlGaAs (x = 0.
4) Layer 18, n-type polycrystalline AlGaAs (x =
0.4) Layer 4 was grown. . This two-step growth was performed in order to obtain a pin junction having good characteristics in the second growth.

Then, with the substrate 1 as the back side, polycrystalline AlGaAs layers 3, 18 and 4 were formed again in the same process. The structure of the produced polycrystalline film is shown in FIG. Then 70
A μm □ mesa structure is formed by chemical etching, and a p-type electrode 6 and an n-type electrode 7 are formed on the etching surface and the mesa structure, respectively.
Was formed (FIG. 6B). When the current-voltage characteristics of this element were measured, rectification characteristics similar to the current-voltage characteristics shown in FIG. 2 were obtained for the elements on both sides of the substrate. Each element emits light only when a forward bias is applied, and FIG.
Two peaks were observed at around 650 nm and around 750 nm as shown in FIG. The peak at 650 nm is based on the band edge of the non-doped polycrystalline AlGaAs (x = 0.4) layer 18, and it is considered that the non-doped polycrystalline AlGaAs layer 18 emits light. Also in this embodiment, similarly to the case of Embodiment 1 shown in FIG. 4, an LED made of a polycrystalline semiconductor is used.
By arranging, the interval of the light emitting points can be halved as compared with the conventional LED array.

[0021]

According to the present invention, it becomes possible to supply a semiconductor optical device using a substrate which is cheaper than a conventional compound semiconductor substrate. Further, since a typical glass as an amorphous substrate has a large area and is easily available, it has become possible to fabricate, for example, a light source (LED array) for an LED printer on one substrate.

[Brief description of drawings]

FIG. 1 is a schematic view of AlGaAs polycrystalline LEDs formed on both sides of a quartz glass substrate described in Example 1 according to the present invention.

FIG. 2 is a graph showing current-voltage characteristics of the AlGaAs polycrystalline LED of FIG.

FIG. 3 is a graph showing an emission spectrum of the AlGaAs polycrystalline LED of FIG.

FIG. 4 is a schematic view of AlGaAs polycrystalline LEDs formed on both surfaces of the quartz glass substrate described in Example 1 according to the present invention.

FIG. 5 is a schematic diagram of an AlGaAs polycrystalline LED formed on a quartz glass substrate with a Cr film according to Example 2 of the present invention.

FIG. 6 is a schematic view of AlGaAs polycrystalline LEDs formed on both sides of the quartz glass substrate described in Example 3 according to the present invention.

[Explanation of symbols]

1 ... Quartz glass substrate, 3, 12, 15 ... P-type polycrystalline Al
GaAs layer, 4, 13, 16 ... N-type polycrystalline AlGaAs
Layers, 5 ... Mesa structure, 6 ... P-type electrode, 7, 17 ... N-type electrode, 10 ... Cr film, 18 ... Non-doped polycrystalline AlGaA
s layer, 20 ... Semiconductor polycrystalline LED

Claims (4)

[Claims] 1. A semiconductor material, which is a polycrystal or polycrystal film formed on both surfaces of a substrate on which epitaxial growth does not occur, and has at least a pn junction or a pin junction in each polycrystal or polycrystal film. , P-type semiconductor and n-type semiconductor
A semiconductor light-emitting device characterized in that it emits light with an n-junction and a pin-junction. 2. The pn junction, the band gap of the semiconductor material forming the pin junction, or the emission mechanism is different on both sides of the substrate, and the emission wavelength is different between the light emitting elements provided on both sides of the substrate. 1. The semiconductor light emitting device according to 1. 3. The substrate on which epitaxial growth does not occur is composed of an amorphous or polycrystal or single crystal structure inorganic material or metal material, or the substrate surface is amorphous, polycrystal or single crystal structure inorganic material or metal material. 3. The semiconductor light emitting device according to claim 1, which is made of a material covered with. 4. The semiconductor light emitting device according to claim 1 is arranged in parallel as a mesa structure, and the respective mesa structures are arranged on both sides of the substrate so as to be offset from each other. Light emitting device.