JPS61280687A - Buried type light emission diode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical fields where inventions succumb] The present invention relates to embedded light emitting diodes.

[Technical background of the invention and its problems] A so-called buried type method in which a double heterostructure is grown on a semiconductor substrate, etched into a mesa shape, and then a layer containing a pn reverse junction is grown to bury the mesa portion. Semiconductor light emitting devices can constrict current in the active layer, so low current drive and high output can be easily achieved. For example, GaInAsP/
The InP-based embedded light emitting diode is constructed as shown in FIG.

An n-type InP buffer layer 4, I n
GaAsP active layer 6, p-type InP cladding layer 8, p-type I
Grow nGaAsP ohmic layer 10 and further 5f
An Oz film is deposited, a circular mask is formed with photoresist, and etching is performed using a bromine-methanol, hydrochloric acid, or sulfuric acid-based etching solution until reaching the buffer 1 layer 4 to form a mesa portion. After this, the mesa side surface is covered with a p-type InP layer 12, an n-type InP layer 14 (current blocking layer), and an I
Fill with nGaAs cap layer 16. After removing the SiO□ film, an electrode 18 on the crystal growth layer side is formed. Thereafter, the back surface of the substrate 2 is polished to form a substrate-side electrode 20, and further, a light extraction window 22 is formed by etching.

In the above configuration, since light is extracted from the substrate 2 side, it is necessary to polish the substrate 2 to a thickness of several tens to 100 μm. However, since the steps of forming electrodes and forming light extraction windows are performed on a substrate that has been polished and made thinner, there is a drawback that the substrate (wafer before being divided into individual chips) is easily broken. Furthermore, since light is extracted from the substrate 2 side, there is a drawback that the coupling efficiency with the fiber is poor.

[Object of the Invention] The present invention reduces cracking of the substrate during the manufacturing process, and
The present invention provides an embedded light emitting diode with high coupling efficiency with fiber.

[Summary of the Invention] According to the buried light emitting diode of the present invention, the cladding layer is formed of a semiconductor crystal layer having a higher refractive index than the buried layer and a narrower forbidden band width than the active layer, and The emitted light is guided to the crystal growth layer side. Therefore, the coupling efficiency with the fiber can be increased. Furthermore, since light is extracted from the crystal growth layer side, there is no need to make the substrate thinner, and cracks in the wafer can be reduced.

[Embodiments of the Invention] The present invention will be described with reference to embodiments in which it is applied to a GaInAS/InP-based embedded light emitting diode.

As shown in FIG. 1, an n-type InP substrate 30 is
P buffer layer 32, GaInAsP active layer 34, p-type G
sP cladding layer 36 and p-type GaInAS to aIn
A P ohmic layer 38 is crystal grown and a 5iOz film is deposited. Next, a photoresist is formed to form a circular mask of 5iOz film. Sulfuric acid etching solution or KO
The ohmic layer 38, cladding layer 36, and active layer 34 are etched using a H+ solution of 1Fe(CM)/HLO to form a mesa portion.

Furthermore, p-type InP layer 401, n-type InP layer 42, n-type GaI
A burying layer consisting of the nASP cap layer 44 is sequentially grown by liquid phase crystal growth to bury the side surfaces of the mesa. After removing the Si0g film, an electrode 46 is attached to the entire surface of the crystal growth layer side (ohmic layer 38 and cap layer 44), and a window smaller than the top surface of the mesa is made in the mesa part by photolithography, and a light extraction window 48 is formed in the electrode 46. form. Next, after polishing the back side of the substrate 30, an electrode 50 was formed on the entire surface.

In the above configuration, the cladding layer 36 and the ohmic layer 3
8 has a lower refractive index than the active layer 34, and the buried layer 40.
By using the GaInASP layer having a larger refractive index than 42, the light emitted from the active layer 34 can be efficiently guided to the light extraction window 48 side using the cladding layer 36 as a waveguide layer.

[Effects of the Invention] According to the present invention, since a light extraction window is formed on the crystal growth layer side and the light emitted from the active layer is guided, the coupling efficiency with the fiber can be increased. .

Furthermore, since there is no need to make the substrate 10 thinner when forming the light extraction window, the substrate will not break.

[Other Embodiments] In the embodiment shown in the second figure, the cap layer 44 of the buried layer
is type 1 GaInAsP, and P+ type GaInA in the mesa part is
A current path was formed by placing it on the side surface of the SP ohmic layer 38. Therefore, the window 48 of the electrode 46 can be made larger than the mesa. Therefore, mask alignment during the formation of the light extraction window becomes easy, and light can be extracted from the entire mesa area, so that the light extraction is improved compared to the embodiment shown in FIG.

The present invention can be modified in various ways without departing from the spirit of the invention, and can be applied to, for example, AlGaAs/GaAs light emitting diodes.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embedded type light emitting diode according to one embodiment of the present invention, Fig. 2 is a sectional view showing an embedded type light emitting diode according to another embodiment of the present invention, and Fig. 3 is a sectional view showing an embedded type light emitting diode according to another embodiment of the present invention. FIG. 2 is a cross-sectional view showing a light emitting diode. 30...Substrate, 32...Buffer 1 layer 3
4... Active layer, 35... Clad layer 3
6...Ohmic layer, 46...Light extraction window agent Kensuke Norichika (and 1 other person) 2nd
figure

Claims (3)

[Claims] (1) A circular mesa including a double heterostructure consisting of a buffer layer of a first conductivity type, an active layer, and a cladding layer of a second conductivity type is provided on a substrate of a first conductivity type, and this mesa is used as an active layer. In the buried light emitting diode embedded with a buried layer having a refractive index smaller than that of the active layer, the cladding layer formed on the active layer has a refractive index larger than that of the buried layer and a band gap smaller than that of the active layer. An embedded light emitting diode characterized by: (2) The embedded light emitting diode according to claim 1, wherein electrodes are provided on the mesa side and on the substrate side, and the electrode on the mesa side has a light extraction window smaller than the mesa. (3) electrodes are provided on the mesa side and the substrate side, the electrode on the mesa side having a light extraction window larger than the mesa;
2. The buried light emitting diode according to claim 1, wherein the buried layer is composed of a plurality of layers, and the uppermost layer is a second conductivity type semiconductor layer.