JPH0728051B2 - Semiconductor light emitting element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A photodiode structure is provided on a semiconductor substrate, a high-reflectance multilayer film is formed on the photodiode structure, and a light emitting portion is provided on the multilayer film, so that light is emitted from the light emitting portion. A semiconductor light-emitting device that can monitor the light emitted from the light-emitting portion by the light that has passed through the high-reflectance multilayer film and reaches the photodiode structure.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device which can be used, for example, as a light source for optical communication and optical information processing, and which is suitable for an IC.

2. Description of the Related Art An example of a conventional surface emitting semiconductor laser is shown in FIG.

In this figure, 21 is an n-side electrode, 22 is an n-GaAs substrate, 23 is an n-AlGaAs cladding layer, 24 is an AlGaAs active layer, and 25 is p-AlGa.
As clad layer, 26 is p-side electrode, 27 is stem, 28 is active layer 24
Is the light emitting area inside. This is because after growing the clad layer 23, the active layer 24 and the clad layer 25 on the substrate 22 by the epitaxial growth method, a circular hole is opened in the substrate 22 until the clad layer 23 is reached, and the absorption layer immediately above the light emitting region 28 is formed. The substrate has a so-called ballast structure manufactured by removing the substrate portion to be formed.

The light emitted in the light emitting region 28 goes up and down, but the light going down is reflected by the electrode 26 (reflected light B2),
It is taken out as an external output light together with the light B1 directed upward.

However, such a structure is indispensable for stabilizing the optical output and compensating for the nonlinear distortion of the optical output / input current, which is required when the light emitting device is applied to high-speed optical communication and analog optical information processing. There were problems that the optical output could not be monitored and that the integration was difficult because the substrate was located above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor light emitting device that can easily monitor the light emission output and can be integrated.

Structure and Effect of the Invention In the semiconductor light emitting device according to the present invention, the photodiode structure is provided on the semiconductor substrate, the high reflectance multilayer film is formed on the photodiode structure, and the light emitting portion is further provided on the multilayer film. Characterize.

Most (for example, about 90% or more) of the light emitted from the light emitting portion toward the substrate is reflected by the multilayer film and becomes the external output light together with the light traveling in the direction opposite to the substrate. The light transmitted through the multilayer film is received by the photodiode structure on the substrate. Since the transmitted light is almost proportional to the external output light, the external output light can be monitored by receiving the transmitted light. Further, since the light emitting portion is provided on the substrate, the light receiving signal amplification circuit of the photodiode structure is provided on the other portion of the substrate, the control circuit for stabilizing the external output light intensity based on the light receiving signal, etc. Can be provided, which opens the way for integration of the light emitting element and the circuit.

Description of Embodiments FIG. 1 shows a first embodiment of the present invention.

1 is a p-type Si substrate, 2 is an n-type region provided therein, and 3 is Al
High-reflectivity multilayer film part in which wGa _1- wAs and AlAs are alternately grown in a thickness of 1/4 of the emission wavelength, 4 is p-type AlzGa _1- z
As lower cladding layer, 5 is AlyGa _1- yAs active layer, 6 is n-type AlxGa
_{The 1-} xAs upper cladding layers, 7, 8 and 9 are electrodes.

An example of an actual drive circuit is shown in FIG. Recombination light emission is generated in the active layer 5 by the negative current injected from the upper cladding layer 6, and the light Al, A2 travels up and down. In the multilayer film portion 3 of AlwGa _1- wAs and AlAs having a thickness of 1/4 of the emission wavelength, the Al mixed crystal ratio w is set to be larger than that of the active layer 5 (however, w <1) and grown in multiple layers. It is possible to easily increase the reflectance to 90% or more, and most of the light A2 incident on this area 3 is reflected by the multilayer film portion 3,
It becomes light A3 and is output to the outside together with light A1 that goes upward. If the reflectance is set to 100% or less, a part of the light A4 is transmitted through the multilayer film portion 3 and is incident on the silicon photodiode composed of the n-type region 2 and the substrate 1. The received light signal can be taken out. It is possible to monitor the external outputs A1 and A3 by this light receiving signal. This monitor output is input to an external electronic circuit, and for example, the light output (A1 + A3) is made constant, or the injection current is compensated so that the light output is linear with respect to the injection current. Return to ₁ .

The light emitting device shown in FIG. 1 is manufactured as follows.

First, the n-type region 2 is provided on the p-type Si substrate 1 (plane orientation does not matter in particular) by diffusion or ion implantation. The area of this n-type region is sufficiently larger than that of a light emitting portion to be formed later. After that, using a non-thermal equilibrium system growth method suitable for thin film growth such as molecular beam epitaxy or metalorganic vapor phase epitaxy,
Multiple layers of lwGa _1- wAs and AlAs are alternately grown to form a multilayer film 3. Here, the thickness of each layer is 1/4 of the set emission wavelength.
Take wavelength. Assuming that the effective refractive index of the light emitting portion is n ₀ , that of the AlwGa _1- wAs layer is n ₁ , that of the AlAs layer is n ₂ , and that of Si is ns, the thickness of each layer of the multilayer film 3 is λ / (4n ₀ ) (Λ: emission wavelength), the reflectance R of the multilayer film 3 with respect to the light of wavelength λ is R = [n ₀ (n ₂ / n ₁ ) ^2N −ns, assuming that N pairs of thin films are grown. _{^{] 2 / [n 0 (n}} 2 / n 1) because represented by ^2N + ns], sets the growing number of layers to be approximately R = 90%.

Furthermore, on the multilayer film 3, a p-type AlzGa _1- zAs lower clad layer 4,
An n- or p-type AlyGa _1- xAs active layer 5 and an n-type AlxGa _1- xAs upper cladding layer ₆ are grown. Here, regarding the mixed crystal ratio of Al, w is set to w> y so that it is transparent to the emission wavelength, and the cladding layer is set to x> y and z> y in order to confine carriers. The shape of the light emitting portion composed of these layers 4 to 6 may be removed by etching after growth so as to be smaller than that of the n-type region 2, or may be selectively grown using a mask. After the above, the electrode 7 with a hole in the center on the layer 6
An electrode 8 is formed on the region 2 and an electrode 9 is formed on the lower surface of the substrate 1.

FIG. 3 shows another embodiment. The electrodes are not shown here. In the embodiment shown in FIG. 1, the substrate 1 is a conductive Si substrate, but as shown in FIG.
By using a double ion implantation method or a double diffusion method.
The p-type region 18 and the n-type region 19 may be provided below the inner light emitting portion to form a pn junction. Further, the photodiode formed of the above pn junction may have a PIN or APD structure.

Needless to say, the conductivity p, n in the above embodiment is not particularly limited and all polarities may be reversed.

FIG. 4 is a conceptual diagram when the light emitting element and its drive control circuit are integrated on the substrate 1. In addition to the light emitting section and the photodiode described above, a widening circuit 11 that widens the light reception signal of the photodiode and a circuit 12 that controls the drive current of the light emitting section are formed on the Si substrate 1.

In the above embodiment, the group III-V heterojunction light emitting portion is formed on the group IV silicon substrate. It should be noted that the above-mentioned multilayer film portion functions as a high reflectance layer and also as a lattice mismatch relaxation layer that absorbs strain caused by lattice mismatch between the silicon substrate and the light emitting portion. is there. Also, since the substrate is silicon that is commonly used for ICs,
As shown in Fig. 4, it is easy to monolithically integrate feedback circuits, control circuits, etc. on the same substrate, and the thermal conductivity of the silicon substrate is higher than that of the GaAs substrate. It is also advantageous over the conventional example in that it solves various problems.

[Brief description of drawings]

1 is a sectional view of an element structure showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing a drive equivalent circuit, FIG. 3 is a sectional view showing another embodiment of the present invention, and FIG. Is a conceptual diagram of integration. FIG. 5 is a sectional view showing a conventional example. 1 ... p-type substrate, 2 ... n-type region, 3 ... high-reflectivity multilayer film part, 4,6 ... cladding layer, 5 ... active layer.

Claims (1)

[Claims] 1. A semiconductor light emitting device comprising a photodiode structure provided on a semiconductor substrate, a high reflectance multilayer film formed on the photodiode structure, and a light emitting portion provided on the multilayer film.