JP3181303B2 - Light emitting element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device, and more particularly to an optical device suitable for application as a light emitting diode or laser for coherent optical communication.

[0002]

2. Description of the Related Art Conventionally, distributed feedback semiconductor lasers have been invented as semiconductor light emitters, that is, light emitting diodes and lasers, in order to enhance the directivity and wavelength selectivity of light. Conventionally, a so-called microcavity laser has been invented as a semiconductor laser having a very small structure. For example, in the Fall of 1982, 43rd Annual Meeting of the Japan Society of Applied Physics, Proceedings 29a-B-6, p. As shown in 127, in a laser having a three-dimensional resonator configuration having a structure of about the wavelength, all light waves are defined by a very small number (several or zero) of eigen (resonance) modes. Not only the transition, but also the spontaneous release process is severely restricted,
Unlike the conventional laser, a coherent light emitting device, a coherent LED, or a low threshold laser can be realized among the thresholds.

[0003]

However, in the above-mentioned distributed feedback semiconductor laser, it is necessary to form a grating on a semiconductor substrate, so that a crystal is likely to have defects during crystal growth, and a high-quality semiconductor laser can be obtained. There are drawbacks, such as difficult to be.

An object of the present invention is to provide a method for overcoming the drawbacks of the distributed feedback semiconductor laser and improving the directivity and wavelength selectivity of light.

Still another object of the present invention is to provide a method for actually fabricating a microcavity laser which is extremely difficult to fabricate with good reproducibility.

[0006]

As a method of improving the directivity and wavelength selectivity of light, the present invention uses a needle-shaped crystal having a pn junction formed on a semiconductor plane. By arranging the needle-shaped crystals so that the interval is an integer multiple of the wavelength as shown in FIG. 1, the light emitted from the needle-shaped crystals having the respective pn junctions is strengthened as shown in FIG. A so-called laser beam having excellent light directivity and wavelength selectivity is emitted from the horizontal direction. In this case, the laser device of the present invention has a great advantage that a high-quality laser can be obtained because it uses a needle-like crystal that is less likely to have a defect than a conventional distributed feedback semiconductor laser.

In the above-described invention, the one-dimensional case is used.
This is because if needle crystals are arranged so that the interval between the needle crystals in two orthogonal directions of the plane is an integral multiple of the wavelength, high-quality laser light can be obtained independently from the two orthogonal directions. A conventional distributed feedback semiconductor laser exhibits a new function that can never be obtained. In addition to the case where the two directions are orthogonal to each other, if the interval between the needle-shaped crystals in any direction is set to an integral multiple of the wavelength, laser light radiated in that direction can be obtained, and the versatility of this element is markedly improved. Results. On the other hand, if the interval between the needle crystals in an arbitrary direction is made different from an integral multiple of the wavelength, light can be prevented from being emitted in that direction. The most effective spacing L between the needle-like crystals when not emitting this light is L = (2N + 1) λ / 2, where λ is the wavelength of the light and N is an integer.
The wavelength λ shown above is, of course, corrected in consideration of the refractive index of the dielectric through which light propagates.

Further, in order to manufacture a microcavity laser, a structure is used which is made of a semiconductor rod having a diameter of 1 μm or less and whose electrical property changes from n-type to p-type in the middle of the rod. FIG. 22 shows the structure. With such a structure, the refractive index inside the rod becomes higher than that of the surroundings as a resonator, and only a very small number of eigenmodes stand due to its small size. And a so-called low threshold laser is realized.

More specifically, if the longitudinal direction of the rod is the crystal axis of the direct transition semiconductor crystal in the (111) direction,
Due to the symmetry of the crystal, more efficient laser oscillation can be achieved.

[0010] Further, as shown in FIG.
When 01 is embedded in the core 202 of the optical fiber for optical communication, light is effectively taken into the optical fiber 203, and a remarkable merit can be obtained as a photoelectric transmission medium.

One method of realizing such a semiconductor rod is to use an extremely thin semiconductor crystal epitaxially grown on a semiconductor substrate. That is, FIG.
As shown in FIG. 4, an extremely thin semiconductor crystal 205 made of, for example, GaAs is formed, and the type of ions to be doped is changed in the middle, for example, from n-type to p-type. A cavity laser can be manufactured.

Also, instead of uniform, very thin crystals,
As shown in FIG. 25, if a structure whose diameter changes periodically in the longitudinal direction of growth is used and the period is set to half the wavelength,
A distributed feedback amplification type semiconductor laser can be manufactured.

[0013]

As shown in FIG. 1, the distance L from one luminous rod to an adjacent luminous rod is set to be an integral multiple of the wavelength λ of the laser light coming out. Thus, the light having the wavelength λ emitted from the light emitting rod induced the excitons in the other light emitting rods, and the light having the wavelength λ having the same phase was laser-oscillated. The distance L at this time is obtained as a spatial average value n ₂ of the refractive index n ₀ around the light emitting rod and the refractive index n ₁ of the light emitting rod, and the thickness of the light emitting rod as W.
The value obtained by multiplying the value of λ / n ₂ by an integer was taken.

[0015] As shown in FIG.
If they are arranged in a square shape and further arranged at equal intervals in the direction of each side, light is emitted in that direction. When an optical element having this structure is used as an optical antenna, it is possible to catch electromagnetic waves propagating from all directions in two dimensions.

Two optical elements are arranged as shown in FIG.
It can be seen that when one is energized and used as a laser oscillator and the other is irradiated with the laser light, it acts as a receiver. As described above, by using two or more optical elements, transmission and reception between the optical elements can be realized as shown in FIG.
Further, a feedback system is provided on this optical element, and once the electromagnetic wave propagating from the surroundings is converted into electricity, converted into light again through the optical element and irradiated on other optical elements, the other elements communicate with each other. And can be applied as an optical neural network.

In the microcavity laser according to the present invention, the dimensions are extremely small, on the order of wavelength, and
A low-threshold laser, a coherent light-emitting device without a threshold, or a coherent LED can be obtained.

More specifically, in the case of the microcavity laser shown in FIG. 22, the radius is as small as 1 μm or less and the length is about the same as the wavelength of light. In addition, the spontaneous emission process as well as the induced transition is remarkably controlled, and a coherent light-emitting device, a coherent LED, or a low-threshold laser having no threshold can be manufactured. In addition, since the electrical properties are changed from n-type to p-type in the middle of the rod, carrier injection light emission occurs due to the pn junction effect, and laser oscillation occurs.

Further, as shown in FIG.
3, the light emitted from the end face of the rod 201 is effectively used as the optical fiber core 2 as shown in FIG.
The light is propagated by being confined in the light emitting element 02, and the coupling efficiency between the light emitting source and the optical fiber is dramatically increased.

[0019]

Examples of the present invention will be described below. In each figure,
The same reference numerals represent the same structure.

Example 1 In order to realize a light emitting rod, GaAs (111) B
Needle-like crystals were selectively grown on the plane of the substrate by reduced-pressure metalorganic chemical vapor deposition. As shown in FIG. 2A, the donor concentration is set to 10 ¹⁸ / c in order to grow the needle-like crystal at a desired place.
de in m ³ - keeping the GaAs (111) follower on B substrate 3 - Cast ion bi - using beam (FIB), G
The seeds underlying the aAs needle crystals were planted.

Thereafter, needle crystals 9 were grown by reduced pressure metalorganic chemical vapor deposition as shown in FIG. 2 (b).
The doping of the needle-like crystal starts growing at n first, and
After the growth of m, the doping is changed to p, and p
Doped needle crystals were grown to 2.1 μm. Therefore, this needle-shaped crystal has a length of 4.2 μm and forms a pn junction at the center thereof. The doping concentration at this time was 10 ¹⁸ / cm ^{3 for} both the donor and the acceptor.

FIG. 2 shows the substrate on which the needle-like crystals are formed.
Spin-on-glass (SOG) was applied as shown in (c). After the application, the coating was cured at 480 ° C. for 30 minutes. At that time, the thickness of the SOG film 6 was 4 μm. Etching was performed with a hydrofluoric acid-based etchant at a thickness of 0.2 μm to remove extra SOG attached to the tip of the needle-shaped crystal. Then, a p-electrode was vapor-deposited on the portion and annealed at 450 ° C. to form an ohmic contact. Gold and zinc were used for the p-electrode.

Next, as shown in FIG. 3A, the back surface of the substrate is polished using fine polishing powder to reduce the total thickness to 100 μm.
m. An n-electrode 5 is deposited on the back surface of this substrate,
Annealed at 50 ° C. Gold germanium nickel was used for the n-electrode.

An electric field was applied to the laser oscillator of FIG. 1 thus manufactured, and its characteristics were examined. In FIG. 1, needle-like crystals are arranged in a line to examine under what conditions laser oscillation is possible. FIG. 8B shows the relationship between the length of the substrate and the intensity (normalized output) P / P ₀ of the oscillated laser light when the needle-shaped crystals are arranged one-dimensionally.

In this embodiment, exactly the same results were obtained even if p and n were reversed.

Example 2 An apparatus similar to that of Example 1 was manufactured by the following process without using FIB.

First, as shown in FIG. 4, a 0.1 μm SiO ₂ film is grown on a GaAs substrate by a thermal CVD method, and then the SiO ₂ film is formed by photolithography and vapor phase etching.
Holes having a diameter of 0.1 μm were formed in the _two films at a distance L interval. On this substrate, n-doped GaAs needle crystals were grown by MOCVD. Thereafter, the process of depositing an electrode on the needle-shaped crystal is exactly the same as that of the first embodiment. The microcavity laser produced by this process also showed the same characteristics as the laser of Example 1.

At this time, the distance L between each needle-like crystal is L = 172.
nm, the thickness W = 100 nm needles, the refractive index n ₀ = 1 the SOG, the refractive index n ₁ = 3.61 needles, spatial averaging of the refractive index value _{n 2 = n 0 + (n} 1 −n ₀ ) × (W / L) = 2.
52, natural number N, number of needle-shaped crystals N ₀ = 7.7 × 10
⁵ (number), emission wavelength λ = 865.4n from needle-like crystal
FIG. 6 (a) shows the relationship between L and the intensity (normalized output) P / P ₀ of the oscillated laser light, where m is the oscillated laser wavelength λ ′ = 344 nm. Current density and P /
The relationship between P ₀ in FIG. 6 (b), Figure 7 the relationship between the under N ₀ and P / P ₀ of W = 100 nm, Re - The light the relationship L and W at the time of the oscillation As shown in FIG.

Embodiment 3 In Embodiments 1 and 2, as shown in FIG.
The distance between the needle crystals 9 on the (111) B n-substrate plane is λ.
/ N ₂ are arrayed so as to be a value obtained by multiplying the value by an integer, and SOG
Was applied. The p-electrode was deposited in the row or column direction as shown in FIG. Thereby, it was possible to emit light only in one row or one column of the needle-like crystal to be emitted. In addition, by energizing only one row or one column, it was possible to obtain an extremely thin laser beam having a width of about the wavelength of the laser beam. The oscillated laser light oscillated only in the direction indicated by the white arrow in FIG. 10, and light in other directions interfered each other and was not observed.

In this embodiment, even if p and n were reversed, exactly the same results were obtained.

Fourth Embodiment In the first and second embodiments, as shown in FIG.
After arranging the needle-shaped crystals 9 on the (111) B semi-insulating substrate plane so that the interval between the needle-shaped crystals 9 is an integral multiple of the value of λ / n ₂ , as shown in FIG. An n-electrode was vapor-deposited before applying SOG on the substrate on which the crystal was formed. The n-electrode formed on the acicular crystal is not so thickly attached because the tip of the acicular crystal faces the direction in which the atoms of the n-electrode (gold-germanium-nickel) fly during vapor deposition. Could be easily removed. Thereafter, SOG was applied and baked in the same manner as in Examples 1 and 2, and a p-electrode was deposited in the same manner as in Example 3. Thereby, it was possible to emit light only in one row or one column of the needle-like crystal to be emitted. In addition, by energizing only one row or one column, it was possible to obtain an extremely thin laser beam having a width about the wavelength of the laser beam. The oscillated laser light oscillated only in the direction indicated by the white arrow in FIG. 10, and light in other directions interfered each other and was not observed.

In this embodiment, exactly the same results were obtained even if p and n were reversed.

Fifth Embodiment In the first and second embodiments, as shown in FIG.
After arranging the needle-shaped crystals 9 on the (111) B semi-insulating substrate plane so that the interval between the needle-shaped crystals 9 is an integral multiple of the value of λ / n ₂ , as shown in FIG. Before applying SOG on the substrate on which the crystals were formed, n electrodes were deposited in rows or columns as shown in FIG. The n-electrode left on the needle-like crystal could be easily removed by etching for the same reason as in Example 4. And SO
G was applied and baked, and a p-electrode was deposited as in Example 2. By adopting such a structure, it is possible to supply electricity to an electrode that comes into contact with a desired needle-like crystal, and emit light only from one of the electrodes.

Needless to say, any desired number of needle-shaped crystals can be emitted.

In this embodiment, the same result was obtained even when p and n were reversed.

Example 6 As shown in FIG. 13, needle-like crystals 9 were arranged on a GaAs (111) B semi-insulating substrate plane such that the interval between the needle-like crystals 9 was an integral multiple of the value of λ / n ₂ . Thereafter, the electrodes were attached using the method for attaching the electrodes shown in Example 4. The direction in which the laser light oscillated was only the direction indicated by the arrow drawn out in FIG.

In this embodiment, even if p and n were reversed, exactly the same results were obtained.

Embodiment 7 As in Embodiment 5, as shown in FIG.
1) The distance between the needle crystals 9 on the plane of the semi-insulating substrate B is λ
After arranging the values of / n ₂ to be integer multiples,
Electrodes were mounted using the method of mounting electrodes shown in Example 4. The direction in which the laser light oscillated was only the direction indicated by the white arrow in FIG.

In this embodiment, even if p and n were reversed, exactly the same results were obtained.

Example 8 As shown in FIG. 9, the distance in one direction between the needle-shaped crystals 9 on the plane of the semi-insulating substrate of GaAs (111) B is a value obtained by multiplying the value of λ / n ₂ by an integer, and the other direction. Were arranged so that the distance between them was half of that value, and then the electrodes were mounted using the method of mounting electrodes shown in Example 4. The direction in which the laser light oscillated was only the direction indicated by the white arrow in FIG.

In this embodiment, exactly the same result was obtained even if p and n were reversed.

Example 9 An optical device was manufactured in the same process as in Example 5. However, a transparent electrode SnO ₂ film was used as a p-electrode deposited on the upper surface of the element.
The distance L between the needle-like crystals was Nλ '/ 2. In this embodiment, the laser light in the horizontal direction was not observed, but the laser light was oscillated in the vertical direction as shown in FIG. This laser light was an extremely coherent light having a spread of about 2.3 × 10 ⁴ (μm ² ) of the electrode area of the device.

In this embodiment, the same result was obtained even when p and n were reversed.

Example 10 A high voltage (1.5 V) was applied to the optical device manufactured in Example 2 to an apparatus as shown in FIG. 16B, and the wavelength oscillated from another semiconductor laser. Laser light near 860 nm was transmitted. At this time, the emitted laser light had much better coherence than the light when it entered.
Thus, the optical device according to the present invention functions not only as a laser light oscillator but also as a resonator.

When a high voltage (1.5 V) is applied to the optical device manufactured in Example 9 and light from another semiconductor laser is incident as shown in FIG. Good light was bent in the vertical direction in FIG. 16B and oscillated.

In this embodiment, exactly the same results were obtained even when p and n were reversed.

Embodiment 11 In the same manner as in Embodiment 10, an apparatus as shown in FIG. 16B was provided, the power supply voltage applied to the optical element was dropped, and an electric measuring instrument was attached instead. A voltage of 5V was applied. When the light of the semiconductor laser was converted into a pulse signal, the optical element correctly read the optical signal.

As shown in FIG. 16 (c), when the interval between the needle-like crystals is variously changed, even if the laser of the incident light is variously changed, the pulse signal of the incident light is not changed. The device was read correctly.

Further, as shown in FIG. 17, the distance between the needle-shaped crystals was changed for each row or column, and electrodes were attached as shown in the figure. The direction and size of the reading and the transmitted direction were indicated by converting them into electricity.

In this embodiment, when p and n were reversed, the signs of the electrical characteristics were reversed.

Embodiment 12 This embodiment will be described with reference to FIG. On an n-type GaAs (111) substrate doped with 10 ¹⁹ Si per cm ³
First, a GaAs / AlGaAs hetero fine needle-like crystal is formed by MOCVD. First, Ga ions are implanted into the substrate 101 by the focused ion beam method. afterwards,
When the crystal is grown, the crystal is selectively grown only in the portion where Ga ions are implanted. By utilizing this, a needle crystal can be formed. The diameter of the Ga ion beam is set to 200 °, and the width of the crystal grown on the
0 °. First, an n-type AlGaAs crystal 102 doped with Si at a dose of 10 ¹⁹ per cm ³ is grown. Next, an i-type GaAs crystal 103 to which no impurity is added is grown, and a p-type AlGaAs crystal 104 in which Zn is doped at 10 ¹⁹ per cm ^{3 is} further grown. AlGaAs
The Al composition ratio in the s crystal is 0.1. n and p
The length of each of the AlGaAs crystals 102 and 104 is 10
The crystal growth time is set to be 00 °. i-type Ga
The length of the As crystal 103 is 300 °.

Next, an AlGaAs layer having an Al composition ratio of 0.2 is grown to a thickness of 2000 ° as the cap layer 105 to stabilize the surface of the needle-like crystal. Since the Al composition of the cap layer 105 is higher than that of the acicular crystal part, the current injected into the acicular crystal does not flow through the cap layer 105. Further, as the cap layer 105, a transparent insulator such as a 2000-degree SiO ₂ film or SOG resin may be used instead of the AlGaAs layer. In this case, the cap layer 105
Before lamination, the surface of the needle-shaped crystal is immersed in an aqueous solution containing NH ₄ S ₂ and Li ₂ S for 20 to 30 hours, heated to 50 ° C., and then heated to 390 ° C. in hydrogen gas for 30 minutes.
By this treatment, the oxide film on the surface of the needle-like crystal is reduced, and a good surface having a reduced non-radiative electron-hole recombination rate on the surface is formed.

The formation of the current injection electrode will be described. Au is deposited on the back surface of the substrate 101 to a thickness of 1000 ° to form a ground electrode 107. An Au / Zn alloy is vapor-deposited on the surface of the cap layer at a thickness of 1000 °, and a pure directional voltage is applied to the pn junction in the needle-like crystal to form an injection electrode 106 for injecting a current.

In the present embodiment, attention has been paid to a single needle-shaped crystal, and a method of forming a pin junction using a heterostructure has been described. By controlling the implantation position of the focused ion beam, an arrangement of needle crystals suitable for laser operation can be made, which will be described in another embodiment.
When the hetero pin junction formed in this embodiment is used, the luminous efficiency of the needle crystal can be increased, and the threshold current density can be reduced when a laser is formed. Also,
In this embodiment, an example in which an n-type substrate is used has been described. However, a hetero-pin junction can be formed by a similar method using a p-type substrate. As a method for selectively growing a needle-like crystal, it is possible to form a mask pattern using an insulating film without using the focused ion beam method. First, an SiO ₂ film is sputter-grown to a thickness of 500 ° on a substrate. A resist is applied thereon, and the diameter is 200 by electron beam exposure.
Make a hole of Å. Thereby, the position where the needle crystal grows can be designated.

In this embodiment, the configuration using a GaAs-based material has been described. In addition, the pin portions of the substrate and the needle-shaped crystal are GaAs and GaAs-In, respectively.
As-GaAs or InP, InP-In, respectively
It can be similarly formed using GaAsP-InP.

Example 13 In producing a laser, a method of arranging needle crystals produced by the method described in Example 1 will be described. Since the (111) plane is used as the substrate surface, the substrate is cleaved into an equilateral triangle as shown in FIG. The cleavage planes corresponding to the base of each triangle are defined as X, Y, and Z. Depending on how the laser light is extracted, the arrangement of the needle crystals 108 and the processing of each cleavage plane differ. The determination of the arrangement of the needle-like crystals is achieved by changing the position of the focused ion beam implantation described in the thirteenth embodiment. From one side,
When the laser beam is taken out so as to be orthogonal to the plane, if the plane is assumed to be X, it is preferable that L1 is set to an integral multiple of the oscillation wavelength and L2 is set to a value other than that. At this time, anti-reflection coatings 109, 110, and 111 are applied to the X, Y, and Z surfaces. Also, two laser beams are extracted from X. If the direction is orthogonal to each of the Y and Z planes, L
The ratio of 1: L2 is set to be the square root of 1: 3, and the square root of the sum of the squares of L1 and L2 may be set to be an integral multiple of the oscillation wavelength.

Embodiment 14 An embodiment of a waveguide type laser using a needle crystal will be described. Acicular crystals are prepared by the methods described in Examples 12 and 13. However, the cleavage of the substrate is not performed yet. A resist is applied on the injection electrode 106 described in Example 12,
After heating, a line-shaped optical waveguide pattern is formed by contact mask exposure, and processed into a shape of the optical waveguide laser 113 by chemical etching. Next, the substrate is cleaved, and the substrate 112 and the laser waveguide 11 having the shapes shown in FIG.
Get 3. The arrangement of the needle crystals in the laser waveguide 113 corresponds to the former condition of the thirteenth embodiment. Finally, the end face of the waveguide is covered with an anti-reflection coating film 114.

Example 15 A microcavity laser shown in FIG. 22 was manufactured.
First, as shown in FIG. 26A, GaAs (111)
The process proceeds to a step of forming a very fine crystal 205 on the B semi-insulating substrate 204 by using a selective growth method. First, GaA
An SiO ₂ film 206 was formed on the substrate by thermal CVD to a thickness of 0.1 mm.
Formed at 6 μm. Then, many holes having a diameter of 20 μm are formed in the SiO ₂ film by using photolithography. An n-doped GaAs microcrystal 205 is grown on a substrate having an SiO ₂ film having this hole pattern by metal vapor deposition (MOCVD). The shape of this crystal can be controlled by the growth conditions. Further, since this crystal has a property of growing in the (111) direction, when a (111) B substrate is used as in this embodiment, the crystal grows perpendicular to the substrate as shown in FIG. In this embodiment, the growth conditions include a substrate temperature of 480.degree.
The source gas ratio of the group (AsH ₃ and trimethylaluminum, respectively) is V / III = 20, and the growth time is 20 minutes. The length of the fine crystal grown at this time was about 3 μm. Next, under the same conditions as in the case of growing n-GaAs, p-
GaAs was grown. The growth time was 20 minutes, the same as in the case of n-GaAs. As a result, fine crystals having a total length of 6 μm were formed. As a dopant, n-GaAs
At the time of growth, monosilane was simultaneously flowed to introduce Si, and n-GaAs with a carrier concentration of 1 × 10 ¹⁸ / cm ³ was obtained. On the other hand, during p-GaAs growth, biscyclopentadiethylmagnesium was flowed, and the carrier concentration was 2 × 10 ¹⁸
/ Cm ³ of p-GaAs was obtained. Next, the grown fine crystal is embedded in a resin 207 as shown in FIG. 26 (a), and the fine crystal is taken out of the substrate together with the resin film as shown in FIG. 26 (b). Polished with a suitable abrasive, and 4 μm wide as shown in FIG.
m. Next, a transparent electrode SnO ₂ film 208 was formed on both surfaces, and a microcavity laser was manufactured. When a current was applied to the obtained microcavity laser to cause oscillation, a low threshold laser having an extremely small oscillation threshold current of 1 μA was obtained.

Example 16 A microcavity laser having a structure shown in FIG. 25 was manufactured. The fabrication method was the same as that described in Example 16, except that a modulation growth was performed in order to introduce a periodic diameter variation in the longitudinal direction. This was caused by changing the magnitude of the V / III ratio from 18 to 22 every 5 minutes during crystal growth.

The oscillation threshold current of the obtained microcavity laser was as low as 1 μA as in Example 15, and the half-width of the emitted light was 1 MHz.

Example 17 A microcavity laser embedded in the core of the optical fiber shown in FIG. 23 was manufactured. In this method, a microcavity laser was manufactured by the method described in Example 14, and one of them was taken out. It was embedded in the core of a quartz optical fiber. As shown in FIG. 27, a small hole was made in the side of the optical fiber to take out the current, and the lead wire 209 was taken out. In the case of the microcavity laser having such a configuration, the coupling efficiency with the optical fiber was as high as 90%.

Example 18 A longitudinal microcavity laser similar to that of Example 16 was produced by periodically changing the crystal composition. As shown in FIG. 28, after the n-type GaAs and n-type GaAlAs in the longitudinal direction is stacked 50 layers alternately, n-type _{Al 0. 5 Ga 0. 5} As, In 0 containing substantially no impurities. ₂ Ga ₀ . ₈ As layer, p-type A
l _{0. 5} Ga _{0. 5} Set As layer, a further p-type GaAs and p-type semiconductor rod GaAlAs is stacked 50 layers alternately. At this time, n-type GaAs, n-type GaAlAs, and p-type
-Type GaAs and p-type GaAlAs layers have an emission wavelength of 4 nm.
Designed in one-half.

In order to allow current to flow in the longitudinal direction, upper and lower electrodes are provided. When a current was applied in the longitudinal direction in the forward direction of the pn junction, a laser with very good coherence was obtained as in Example 16.

Example 19 After growing 1 μm of n-type GaAlAs in the longitudinal direction of the crystal, a GaAs layer containing almost no impurities was stacked to a thickness of 2 nm, and a semiconductor rod on which p-type GaAlAs was grown at 1 μm was used as a rod. 2 μm at intervals approximately equal to the diameter
Arranged in the corner area. In order to pass current in the longitudinal direction, electrodes were provided on the upper and lower sides, and when current was passed in the forward direction of the pn junction,
As in Example 16, a laser having very good coherence was obtained.

Example 20 FIG. 30 is a schematic cross-sectional view of a pn junction light emitting device in which a crystal surface is treated with sulfur (S) or selenium (Se) to stabilize the crystal surface. In this figure, 401 is a substrate and n
The mold InPs 402 and 403 are made of InGaAs at portions constituting needle crystals. Reference numeral 404 denotes a surface stabilization layer formed by performing the above-described S or Se treatment on the outer surface of the needle-like crystal. 406, 407 and 408 represent n of the acicular crystal.
Area, a non-doped area and a p-type area. Here, the n-type region is 1 μm in length, and the p-type region is 1 μm in length.
And the non-doped region is 10 nanometers. Also, 1
09 and 410 are electrodes. When a positive bias is applied to the electrode 409 and a negative bias is applied to the electrode 410, current flows in the direction indicated by 411. The current path of the needle-shaped crystal denoted by 402 is indicated by D ₂ , and the thickness of the current path is denoted by D _2.
3 also thickness, including described in D _1. In this embodiment, D ₁ is 2
0 nanometers - D ₂ In torr 15 nanometers - a torr. When the surface stabilization treatment is performed by S or Se, the thickness of the surface depletion layer 403 of the acicular crystal is reduced by about 20 to 60% due to the presence of the surface stabilization treatment layer 404. Therefore, the thickness D ₂ of the current path 402 of the acicular crystal is 10
From about 20% to about 16 to 18 nanometers. Next, when a current 411 was passed, light emission from a portion centered on the non-doped region 407 was observed.

FIG. 25 shows a graph of the light emission gain versus the light emission wavelength of the light emitting device. In the figure, graphs are shown with and without the stabilization treatment of the surface of the needle crystal. FIG.
As is clear from the above, when the surface was stabilized,
It can be seen that the emission wavelength shifts to the longer wavelength side by about 0.05 μm. The reason why the emission wavelength shifts to the longer wavelength side when the surface is stabilized is that the thickness of the depletion layer on the crystal surface decreases and the width of the current path for confining the carriers increases. On the other hand, the gain increases about 1.5 to 2 times. This is because the stabilization of the crystal surface reduced the rate of non-radiative recombination.

FIG. 32 is a graph showing the operating time dependency of the light emitting device. This graph shows the change over time in the peak light emission intensity of the light emitting element.
If no surface stabilization treatment, peak in a range leading to 10 ³ to 10 ⁴ hours - click emission intensity decreases gradually with the operation time, it is seen to decrease rapidly at 10 ⁴ hours or more. On the other hand, when the surface stabilization treatment was performed, it was found that there was almost no change in the peak emission intensity in the range from 10 ⁴ to 10 ⁵ hours. That is, it can be seen that the life of the light emitting element is extended by 10 times or more by the surface stabilization treatment.

[0068]

As described above, according to the present invention, a semiconductor laser can be realized by disposing conductive rods at intervals of an integral multiple of the oscillation wavelength, and the same device can be used. Thus, an optical antenna can be manufactured.

As described above, according to the present invention,
Since a microcavity laser having an extremely small threshold current, a coherent light emitting element without a threshold value, and a coherent LED can be actually manufactured, it is a very effective key device in the optical communication field. This is because only a small number of modes are involved in laser oscillation by the microcavity. Further, since the microcavity laser of the present invention can be embedded in the core of an optical fiber, there is a merit that the coupling efficiency between the optical fiber and the laser is drastically increased, and the merit obtained in the industry cannot be overestimated. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a light emitting element or an optical antenna using a needle-like crystal having a pn junction according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a manufacturing process of a light-emitting element according to an example of the present invention.

FIG. 3 is a view showing a manufacturing process of a light-emitting element according to an embodiment of the present invention and a needle-like crystal in which a portion to be grown by lithography is controlled.

FIG. 4 is a view for explaining drilling by lithography.

FIG. 5 is a diagram for explaining attachment of an n-electrode.

FIG. 6 is a graph showing light emission characteristics of the optical device according to the example of the present invention.

FIG. 7 is a graph showing light emission characteristics of the optical device according to the example of the present invention.

FIG. 8 is a graph showing light emission characteristics of the optical device according to the example of the present invention.

FIG. 9 is a diagram illustrating an optical element that emits light in one direction according to an embodiment of the present invention.

FIG. 10 is a view showing an optical element which emits light in two directions according to the embodiment of the present invention and mounting of its electrodes.

FIG. 11 is a view showing an optical element which emits light in two directions and mounting of its electrodes according to the embodiment of the present invention.

FIG. 12 is a view showing an optical element which emits light in two directions according to the embodiment of the present invention and the mounting of its electrodes.

FIG. 13 is a diagram showing an optical element that emits light in three directions according to an embodiment of the present invention.

FIG. 14 is a diagram showing an optical element that emits light in five directions according to an embodiment of the present invention.

FIG. 15 is a diagram showing an optical element that emits light in the n direction according to an example of the present invention.

FIG. 16 is a diagram showing an example of an optical element, an optical amplifier, and an optical direction changer that emit light in the longitudinal direction of a needle-like crystal according to an example of the present invention.

FIG. 17 is a diagram for explaining a light direction searcher according to the embodiment of the present invention.

FIG. 18 is a diagram showing an optical operation device according to an embodiment of the present invention.

FIG. 19 is a cross-sectional view of a diode structure having a hetero pin-shaped needle crystal according to an example of the present invention.

FIG. 20 is a view for explaining a laser structure having a needle-like crystal arranged on an equilateral triangular substrate according to the embodiment of the present invention.

FIG. 21 is a top view of a waveguide type laser structure according to an embodiment of the present invention.

FIG. 22 is a view showing a microcavity laser according to the embodiment of the present invention.

FIG. 23 is a diagram illustrating a microcavity laser according to an embodiment of the present invention embedded in the core of an optical fiber.

FIG. 24 is a view for explaining a state of growth of a fine crystal.

FIG. 25 is a diagram showing a microcavity laser whose diameter in the longitudinal direction periodically changes according to the embodiment of the present invention.

FIG. 26 is a diagram showing a method for manufacturing a microcavity laser according to an example of the present invention.

FIG. 27 is a diagram showing a configuration for realizing a microcavity laser according to an embodiment of the present invention embedded in an optical fiber.

FIG. 28 is a view for explaining a composition modulation type vertical microcavity laser according to an example of the present invention.

FIG. 29 is a view for explaining a multi-rod laser according to an embodiment of the present invention.

FIG. 30 is a schematic cross-sectional view of a light emitting device using needle-like fine crystals according to an example of the present invention.

FIG. 31 is a graph showing a relationship between gain and emission wavelength of a light emitting device according to an example of the present invention.

FIG. 32 is a graph of relative peak light emission intensity versus operation time of a light emitting device according to an example of the present invention.

[Explanation of symbols]

1 ... n-doped GaAs needle crystal, 2 ... p-doped GaAs
Needle crystal, 3 ... n-doped GaAs substrate, 4 ... p electrode, 5
... n electrode, 6 ... SOG, 7 ... hole, 8 ... semi-insulating substrate, 9 ...
Needle crystal having a pn junction, 10... transparent electrode SnO ₂ 1
01-substrate, 102-n-type AlGaAs, 103-i-type GaAs, 104-p-type AlGaAs, 105-cap layer, 106-injection electrode, 107-grounding electrode, 10
8-needle crystal, 109, 110, 111-anti-reflection coating film, 112-substrate, 113-laser waveguide, 11
4-Non-reflective coating film, 301 ... GaAs substrate, 3
02 ... n-type GaAs, 303 ... n-type GaAlAs, 30
4 ... n-type _{Ga 0. 5 Al 0. 5} As, 305 ... In 0. 2 Ga 0. 8
As, 306 ... p-type _{Ga 0. 5 Al 0. 5} As, 307 ... p -type GaAlAs, 308 ... p-type GaAs, 310 ... GaA
s substrate, 311 ... n-type GaAs 312 ... n-type GaAlA
s, 313 ... GaAs active layer, 314 ... p-type GaAlA
s, 315: p-type GaAs 401: substrate, 402: current path of acicular crystal, 403: surface depletion layer of acicular crystal, 404
... Surface stabilization layer, 405 ... Transparent insulating film, 406 ... n
Region, 407: non-doped region, 408: p-type region, 409: electrode, 410: electrode, 411: current

Continuing from the front page (72) Inventor Toshio Katsuyama 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo In the Central Research Laboratory of Hitachi, Ltd. (72) Inventor Toshiyuki Usagawa 1-280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Masamitsu Yazawa 1-1280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Hitachi, Ltd. Person Toshiaki Masuhara 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd.Central Research Laboratories (72) Inventor Gerard P. Mogan 1-1280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Hiroshi Kakibayashi 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) References JP-A 1-39805 (JP, A) Akira 53-31987 (JP, A) JP flat 2-84787 (JP, A) Applied Physics L etters Vol. 58, No. 10, pp. 1080-1082 (March 11, 1991) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 G02B 6/16 H01L 27/15 H01L 33/00 JICST file (JOIS )

Claims (11)

(57) [Claims] 1. A formed on the semiconductor substrate upper even and pn junction
Properly has a semiconductor rod comprising a pin junction, the pn
The surface of the junction or pin junction is the length of the semiconductor rod
A plane parallel to a direction intersecting the direction, the intervals between the semiconductor rods are made substantially equal , and
A first electrode on a plate side, wherein the semiconductor rod of the semiconductor rod is
The end opposite to the body substrate is formed in contact with the second electrode.
Emitting element characterized by there. 2. A pn junction formed on an upper portion of a semiconductor substrate.
Or a semiconductor rod including a pin junction,
The surface of the junction or pin junction is the length of the semiconductor rod
The semiconductor having a plane parallel to a direction intersecting the direction, and
A first electrode on the substrate side, wherein the half of the semiconductor rod is
The end opposite to the conductive substrate is formed in contact with the second electrode.
And a distance between the semiconductor rods is substantially an integral multiple of a wavelength of emitted light . 3. A pn junction formed on a semiconductor substrate and having a pn junction
Or a semiconductor rod including a pin junction,
The surface of the junction or pin junction is the length of the semiconductor rod
The semiconductor having a plane parallel to a direction intersecting the direction, and
A first electrode on the substrate side, wherein the half of the semiconductor rod is
The end opposite to the conductive substrate is formed in contact with the second electrode.
And wherein the interval between the plurality of semiconductor rods in one direction is substantially an integral multiple of the wavelength of the emitted light, and is substantially different from the integral multiple of the wavelength of the emitted light in the other direction. Light emitting element . 4. A different conductivity type formed on a semiconductor substrate.
Having a semiconductor quantum wire crystal including a junction, wherein the different conductivity type
The plane of the junction crosses the longitudinal direction of the semiconductor quantum wire crystal
Have a plane parallel to the direction of
Are substantially equally spaced, and on the semiconductor substrate side
A second electrode on a side opposite to the semiconductor substrate;
A light-emitting element having a pole. 5. A substrate having a cross-sectional diameter of 10 on a conductive substrate.
A region irradiated with atoms or molecular ions focused to a beam shape of 00 nm or less, or a diameter of 1000 n provided on an insulating film formed on the conductive substrate.
m or less, and a needle-shaped semiconductor material is selectively grown in a hole region of m or less, and the configuration of the needle-shaped semiconductor material is pi-
The light absorption edge photon energy of a material portion having an n-type electrical property distribution and exhibiting p and n-type electrical properties is an intrinsic type i
A light emitting element including a structure in which the energy is set to be higher than the light absorption edge photon energy of the shaped portion, the axial direction of the needle-shaped semiconductor portion is perpendicular to the substrate surface, and the width is 1000 nm or less.
Child . 6. A different conductivity type formed on a semiconductor substrate.
A semiconductor rod including a junction, wherein
The plane is parallel to the direction crossing the longitudinal direction of the semiconductor rod
And the spacing between these semiconductor rods is substantially equal.
Spacing, and having a first electrode on the semiconductor substrate side,
An end of the semiconductor rod opposite to the semiconductor substrate is a second end.
2 is formed in contact with the two electrodes, and the periphery of the semiconductor rod is
A half having a larger light absorption edge energy than the semiconductor rod.
A light-emitting element covered with a conductor material or an insulator material. 7. A different conductivity type formed on a semiconductor substrate.
Having a quantum wire crystal including a junction, the hetero-conductivity type junction
The plane is parallel to the direction crossing the longitudinal direction of the quantum wire crystal
And the distance between these quantum wire crystals is substantially equal.
Spacing, and having a first electrode on the semiconductor substrate side,
A second electrode on a side opposite to the semiconductor substrate;
The electronegativity around the crystal is smaller than that of the quantum wire crystal
Light-emitting element covered with material or insulator material. 8. A semiconductor rod having a diameter of 1 μm or less, wherein the diameter of the semiconductor rod periodically changes in a longitudinal direction of the semiconductor rod at a wavelength of 1 / n (n: an integer), and Has a change from n-type to p-type in the middle of the rod
Light emitting element . 9. A semiconductor rod having a plurality of semiconductor rods each having a diameter of 1 μm or less, wherein the diameter of the semiconductor rod periodically changes in a longitudinal direction of each of the semiconductor rods at a half of a wavelength (n: an integer), And, in the middle of each of the semiconductor rods, from n-type to p-type.
A light emitting device having a change to a mold, wherein the plurality of semiconductor rods are embedded in the core of the optical fiber in a longitudinal direction.
Element . 10. The light emitting device according to claim 9 , wherein a crystal composition is not uniform in a longitudinal direction of said semiconductor rod. 11. The light emitting device according to claim 9 , wherein a crystal composition in a longitudinal direction of said semiconductor rod changes periodically.