JP2834757B2 - Light emitting device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention integrates a solid-state laser material and a semiconductor laser to obtain an emission output having the same wavelength as the oscillation wavelength of the solid-state laser. The present invention relates to a light-emitting element that has achieved high performance and high stability, and a method for manufacturing the same.

[Prior Art] Conventionally, a lamp has been mainly used for exciting a solid-state laser. In recent years, for miniaturization and high efficiency, a method of exciting a single crystal for a solid-state laser with a semiconductor laser or a method of adding a solid-state laser emission center element as an impurity to a semiconductor laser light-emitting layer has been attempted.

FIG. 4 shows a conventional semiconductor laser excitation type (external excitation type).
FIG. 2 is a schematic configuration diagram of an Nd; YAG laser. In the figure, 11
Is a laser diode array which is a pump light source of the YAG laser, 12 is a collimating lens, 13 is a focusing lens for condensing the laser light from the diode array 11 and made to enter a rod, and 14 is a laser rod Nd: Y
AG. Nd: YAG14 plays the role of a wavelength converter. 15 is KTP (Kalium Triphosphat) for wavelength shaping
e) and 16 are light beam shaping lenses having a filter coating.

In addition to the solid-state laser having such a configuration, there is an internally pumped semiconductor laser in which a solid-state laser emission center (a rare earth element) is added to a semiconductor laser light-emitting layer.

[Problems to be Solved by the Invention] Meanwhile, in a semiconductor laser pumped solid-state laser having a configuration as shown in FIG. 4, a single crystal for a solid-state layer (Nd: Y in the figure)
Introducing semiconductor laser light into AG rod 14 and Nd: YAG
There is a problem that a complicated optical system is required to extract the wavelength-converted light from the rod 14.

The light absorption wavelength range of the Nd: YAG rod 14 is narrow as shown in the graph of FIG. 5, while the wavelength range of the semiconductor laser light (LD) is used in a narrow band as shown by a dashed line in FIG. The central wavelength drift of the laser beam due to temperature is as large as about 10 ° / ° C. Therefore, when the center wavelength of the laser light (LD light) fluctuates due to temperature fluctuation, the light absorption wavelength region where the absorption rate peaks in FIG. 5 and the laser light wavelength region where the emission intensity peaks in FIG. Nd: Y by semiconductor laser light
There was a problem that it was difficult to operate the AG rod efficiently and stably.

On the other hand, when a solid-state laser emission center (rare earth element) is added to the semiconductor laser emission layer (internal excitation type), the relative position between the energy level of the semiconductor laser emission layer base material and the base level and excitation level of the added rare earth impurity. The design is very difficult, and there is a problem that doping the rare earth element at a high concentration in order to increase the luminous efficiency deteriorates the crystallinity and lowers the luminous efficiency and the lifetime.

An object of the present invention is to improve the optical coupling between a semiconductor light emitting unit and a light wavelength conversion unit containing a rare-earth element in view of the above-mentioned problems in the conventional type, and to achieve a compact, high-efficiency and mechanical device without the need for a complicated optical system. It is an object of the present invention to provide a light-emitting element structure capable of obtaining a laser beam from a rare earth element, which is thermally and thermally stable.

[Means and Actions for Solving the Problems] To achieve the above object, a light-emitting element according to the present invention is provided on a semiconductor single crystal layer having a first type (n-type or p-type) conductivity. A first type cladding layer, an active layer, a second type (p-type or n-type) cladding layer, and a same second type electrode layer in the same order, and further in proximity to or adjacent to the active layer. In addition, a stripe-shaped wavelength converter doped with trivalent rare earth ions, which is photoexcited by the emission energy of the active layer, is provided.

Such a light emitting element is formed by epitaxially laminating these layers in sequence on an n-type or p-type semiconductor single crystal substrate, and then etching from the surface of the electrode layer to a position close to or adjacent to the active layer by stripe-shaped grooves. And then burying a stripe-shaped wavelength conversion portion such as glass doped with trivalent rare earth ions in the groove by sputtering.

The configuration of the light emitting device according to the present invention will be described in detail with reference to FIG. Here, the first type will be described as n-type, and the second type will be described as p-type, but the same applies when these types are interchanged. Further, the case where Nd ³⁺ is used as the trivalent rare earth ion to be doped into the wavelength converter will be described, but the present invention is not limited to this.

In FIG. 1, a semiconductor laser has an n-type clad layer 2 and an active layer (light-emitting layer) 3 laminated on an n-type substrate wafer 1, and a p-type clad layer 4 is further laminated to cleave a surface perpendicular to the layer surface. Create by doing. When a forward current is applied between the P-side and N-side electrodes of such a semiconductor laser, light is emitted from the active layer 3 to generate light of the LED type wavelength spectrum shown in FIG. This light is reflected by the mirror at the opposite cleavage plane, and grows into an LD-type wavelength spectrum that emits light only at the resonance wavelength.

Here, it is difficult to match the peak wavelength of the emission intensity of the LD-type wavelength spectrum with the peak of the Nd: YAG absorption wavelength in FIG. 5 due to temperature fluctuation and the like as described above. An LED-type spectrum or a superluminescent-type spectrum having an intermediate spectral spread between the LD and the LED is used for exciting Nd: YAG.

For this reason, in the light emitting device according to the present invention, as shown in FIG. 1, the gap between the Nd-doped (wavelength conversion) region 7 and the active layer 3 is on the order of the emission wavelength, and the optical coupling is strengthened. Also,
The cleavage plane 9 has an AR (Anti refle) that lowers the excitation light reflectance.
ction) Coating is applied. However, for about 1060 nm, which is the emission wavelength of Nd: YAG, in order to extract strong light, the light extraction surface is AR-coated and the opposite surface is HR (High ref).
lection) In some cases, it is coated.

As described above, the emission light (the LED type spectrum or the spear luminescent type spectrum in FIG. 6) of the semiconductor active layer 3 having a light emission intensity of a certain level or more in a relatively wide wavelength range,
Excitation of the stripe (strip-shaped) wavelength conversion layer 7 doped with trivalent rare earth ions provided adjacent to or adjacent to (for example, parallel to) the active layer 3 to obtain a laser output with good temperature stability. Can be

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples.

First, as a first embodiment, a light emitting device in which an AlGaAs / GaAs semiconductor and an Nd-doped glass wavelength converter are combined will be described.

Referring to FIG. 2a, the light emitting device of the present embodiment first has an n-Al _0.3 Ga _0.7 layer having a thickness of about 2 μm on the (100) plane of n-GaAs substrate 1 having a carrier concentration of 2 × 10 ¹⁸ cm ^−3. As (carrier concentration 1 ×
10 ¹⁸ cm ^-3 ) The cladding layer 2 is epitaxially laminated by MOCVD, and an undoped Al _0.09 Ga
_{The 0.91} As active layer 3 is laminated. The Al ratio of the active layer 3 is such that its emission center wavelength is about 808 nm, which is the Nd absorption wavelength of the wavelength converter.
Choose 0.09 so that Subsequently, the p-
Al _0.3 Ga _0.7 As (carrier concentration 1 × 10 ¹⁸ cm ⁻³ ) cladding layer 4 and 0.3 μm thick p-GaAs (carrier concentration 2 × 1
0 ¹⁸ cm ⁻³ ) The electrode layer 8 is laminated.

Next, as shown in FIG.
(The optical interaction between the active layer 3 and the Nd-doped glass stripe 7 is adjusted by this gap.) The surface is dug by etching in a stripe shape up to the position, and Nd-doped glass (for example, SiO ₂ ) is formed by sputtering. , Si ₃ N ₄ , Al ₂
O ₃ etc. is embedded. In the present embodiment, Nd-doped SiO ₂
Was used.

Thereafter, metal electrodes 5 and 6 were formed on the upper and lower surfaces by vapor deposition. Then, a mirror surface is formed by a dry etching method along a (110) plane perpendicular to the epitaxial plane and perpendicular to the axial direction of the stripe 7, and finally parallel to the axial direction of the stripe 7 and perpendicular to the mirror surface. Cleave the surface and cut out the laser chip.

In order to selectively extract laser light with a wavelength of 1060 nm by Nd, one surface of the mirror surface is coated with an AR reflection film that has low reflection at wavelengths of 1060 nm and 808 nm, and the other surface has high reflection and wavelength of 1060 nm. What is necessary is just to coat the reflection film which becomes low reflection with respect to 808 nm.

FIG. 2b shows a case where the mirror surface 9 is formed by cleavage, and the Nd-doped glass 7 does not reach the cleavage surface.
The glass stripe portion 7a near the mirror surface 9 is tapered.

The embodiment of the array laser using multiple stripes has been described above. Note that the number of stripes may be adjusted depending on the power used. In this embodiment, Nd is used as the wavelength conversion unit 7.
Although doped glass is used, glass doped with trivalent rare earth ions other than Nd ³⁺ can be used. In that case, the emission wavelength of the semiconductor active layer may be selected according to the absorption wavelength of each element.

Another Embodiment FIG. 3 shows a cross section of a light emitting device according to another embodiment of the present invention.

In FIG. 2a, the Nd-doped glass 7 is filled with p-Al
_0.3 Ga _0.7 As it remains in the cladding layer 4, with the light-emitting element shown in FIG. 3 Embedding Nd-doped glass, the active layer 3
Further, the influence is applied to the n-Al _0.3 Ga _0.7 As clad layer 2. Thereby, the Nd-doped stripe 7 can be photoexcited by effectively utilizing the light emission energy of the active layer 3. Further, the propagation of the light wave along the axial direction of the stripe 7 can be controlled.

In the above embodiment, the wavelength conversion section 7 is made of glass doped with trivalent rare earth ions. However, as shown in FIG. 7, the photocurrent confinement semiconductor layer 29 of the conventional BH type semiconductor laser is trivalent. Rare earth ions may be doped. In addition,
In FIG. 7, the same reference numerals as those in FIG. 1 indicate common parts.

Further, a trivalent rare earth ion may be doped into the cladding layer of the conventional semiconductor laser in the same manner.

[Effects of the Invention] As described above, according to the present invention, the wavelength conversion unit disposed at a position close to or adjacent to the active layer and optically coupled is excited by the light emitted from the active layer. Therefore, a light-emitting element having good stability against a change in operating temperature is provided because the emission spectrum of the active layer is wide and the temperature stability is good (drift is as small as several Å / ° C. or less). In addition, since it is an integral type, it is stable against mechanical vibration.

On the other hand, the semiconductor active layer may be an undoped active layer, and it is not necessary to dope impurities at a high concentration. Therefore, the semiconductor active layer has good crystallinity and can prevent a decrease in luminous efficiency and life of the active layer.

[Brief description of the drawings]

FIG. 1 is a structural view of a light emitting device according to the present invention, FIG. 2 is a sectional view and a perspective view of an array stripe type laser according to one embodiment of the present invention, and FIG. FIG. 4 is a schematic view of a conventional semiconductor laser pumped Nd-YAG laser, FIG. 5 is a graph showing the light absorption characteristics of an Nd-YAG rod, FIG. FIG. 7 is an explanatory diagram of an emission spectrum of a semiconductor light emitting device. FIG. 7 is a cross-sectional view of a BH type semiconductor laser. 1: n-type substrate, 2: n-type cladding layer, 3: active layer, 4: p-type cladding layer, 5: n-side electrode, 6: p-side electrode, 7: Nd-doped stripe, 8: p-type electrode layer, 9: The cleavage face.

Claims (2)

(57) [Claims] 1. A first type clad layer, an active layer, a second type clad layer, and a second type electrode on a semiconductor single crystal layer having a first type conductivity. A stripe further comprising a layer, in a position close to or adjacent to the active layer, and in the second type cladding layer, doped with trivalent rare earth ions so as to be photoexcited by the luminous energy of the active layer. A light-emitting device comprising a wave-shaped wavelength converter. 2. A first type cladding layer, an active layer, a second type cladding layer, and a second type electrode on a semiconductor single crystal substrate having a first type conductivity. Layers are epitaxially laminated, and a groove is stripped by etching from the surface of the electrode layer to a position close to or adjacent to the active layer, and a stripe is formed by doping trivalent rare earth ions into the groove by sputtering. A method for manufacturing a light emitting device, wherein a wavelength converter is embedded.