JPH04338680A - Superluminescent diode - Google Patents

Abstract

PURPOSE:To obtain an SLD having a smooth and unimodal spectral shape by so setting a laminating order of active layers in multiple active layers to an irregular order that electrons and holes do not fall in the active layer having a lowest band gap energy. CONSTITUTION:Multiple active layers 10 are formed by laminating two or more active layers in such a manner that the active layers having a band gap energy corresponding to a part of a vertex of a spectral shape including a unimodal and broad spreading are thickened in a distribution and the active layers having a band gap energy corresponding to each part isolated from the vertex toward a bottom, are thinned in a distribution toward the bottom. The laminating order of the layers is so set to an irregular order that electrons and holes do not concentrically fall in the active layer having a lowest band gap energy.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to super luminescent diodes (hereinafter referred to as SLDs), and particularly to SLDs in which the spectral shape of spontaneously emitted light is unimodal and broad.

0002

2. Description of the Related Art In recent years, SLDs, which are positioned between semiconductor lasers and light emitting diodes, have attracted attention. This light-emitting device has a broad spectrum spread like a light-emitting diode, and can emit light with as high output as a semiconductor laser. Therefore, the SLD has the advantage of being able to extract high-output, incoherent light with good directionality. Taking advantage of this advantage, it is being used as a light source for fiber gyros, which is a component of inertial navigation systems that obtain moment-by-moment position information of aircraft and ships and guide them to their destinations.

The key points in the structure and manufacture of SLDs are how to suppress laser oscillation, widen the spectrum width of spontaneously emitted light, and increase its optical output.

FIG. 4 is a cross-sectional view showing the basic structure of a conventional SLD. In the figure, 1 is an n-electrode, 2 is an n-type G
an aAs substrate, 3 an n-type AlGaAs first cladding layer;
4a is a first active layer, 4b is a second active layer, and these two
The two active layers 4a, 4b have slightly different bunt gap energies. 5 is the two active layers 4
sandwiching a and 4b, and forming a higher bandgap than them.
Guide layer with energy, 6 p-type AlGaAs second cladding layer, 7 n-type GaAs layer, 8 p electrode, 9
is a Zn diffusion region.

FIG. 5 is a top view with the n-electrode removed from the conventional SLD shown in FIG. You can see that it is tilted, but this is to suppress laser oscillation. Further, the reflectance at the laser end face is set to 3% on the front surface and 3% on the rear surface to suppress laser oscillation.

FIG. 6 shows a band diagram of the conventional SLD shown in FIG. In the figure, EgC, Eg
G, Eg1, and Eg2 are the first and second cladding layers 3 and 6, the guide layer 5, the first active layer 4a, and the second active layer 4b, respectively.
The bandgap energies are shown in order of increasing bandgap energy. Also, λC in the figure
, λG , λ1 , λ2 indicate wavelengths corresponding to the bandgap energies of the first and second cladding layers 3 and 6, the guide layer 5, the first active layer 4a, and the second active layer 4b, respectively. In order, the wavelength becomes shorter.

Next, the operation will be explained. SLD pn
In the forward direction with respect to the junction, that is, positive to p electrode 8, positive to n electrode 1
When a negative voltage is applied to the Zn diffusion region 9, electrons and holes are efficiently injected into the two active layer portions 4a and 4b directly below the Zn diffusion region 9, and spontaneous emission light and stimulated emission light are emitted from the device end face. . The shape of this spectrum is shown in FIG.

FIG. 7 is a diagram showing the spectral shapes of the emitted spontaneous emission light and stimulated emission light, corresponding to the band diagram of FIG. center wavelength λ
The spontaneous emission light and the stimulated emission light of 1 are emitted from the second active layer 4b, and the spontaneous emission light and the stimulated emission light of the center wavelength λ2 corresponding to the band gap energy Eg2 are emitted, and each of them has a spectral shape that is added. I understand that. In this way, since the two spontaneously emitted lights and the stimulatedly emitted light are added together, the spectrum has a broader spread than the spectrum of the spontaneously emitted light and the stimulatedly emitted light from one active layer.

[0009]

[Problem to be solved by the invention] Since the conventional SLD was configured as described above, the spectral shape was spread, but since it was bimodal rather than a gentle single peak, the light focusing ability of the lens was poor. .

The present invention has been made to solve the above-mentioned problems, and aims to obtain an SLD having a wide, gentle, unimodal spectral shape.

[0011]

Means for Solving the Invention The SLD according to the present invention has a thick active layer having a bandgap energy corresponding to the apex portion of a spectrum shape having a single peak and broad spread, and has a bandgap energy that is thick from the apex to the bottom. A multi-activated active layer is formed by laminating two or more active layers with various band gap energies so that the active layers with band gap energies corresponding to each separated part become thinner in distribution toward the bottom. bandgap layer.
Provided between the first and second cladding layers with high energy,
In addition, the order in which the active layers in the multi-active layer are stacked is irregular so that electrons and holes are not concentrated in the active layer with the lowest band gap energy.

0012

[Operation] In this invention, the spectral shape corresponds to the apex portion of a spectrum shape having a single peak and a broad spread.
The active layer with bandgap energy is thick, and the active layer with bandgap energy corresponding to each part away from the top toward the bottom becomes thinner toward the bottom. A multi-active layer formed by laminating two or more active layers with energy is combined with a first active layer having a larger bandgap energy,
between the second cladding layers, and the stacking order of each active layer in the multi-active layer is irregular so that electrons and holes do not concentrate and fall in the active layer with the lowest band gap energy. Therefore, it is possible to obtain an SLD with a gentle, unimodal spectral shape.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing the front side of an SLD according to an embodiment of the present invention. In the figure, 10 indicates an active material having a bandgap energy corresponding to the apex portion of a spectrum shape having a single peak and broad spread. The active layer is thick and has two or more layers with various bandgap energies so that the active layer has a bandgap energy corresponding to each part separated from the top toward the bottom and becomes thinner toward the bottom. This is a multi-active layer formed by stacking active layers, and the stacking order of each active layer in the multi-active layer 10 is set so that electrons and holes do not concentrate and fall in the active layer with the lowest band gap energy. It is in an irregular order. Further, in this example, the active layer is composed of a total of 12 layers. As shown in FIG. 5 of the conventional example, when viewed from above, the Zn diffusion region 9 is not parallel to the resonator direction but is inclined at a certain angle in order to suppress laser oscillation. Other parts are the same as or equivalent to conventional parts.

FIG. 2 is a band diagram of the SLD of this embodiment shown in FIG. In the figure, EgC, Eg3
, Eg4, Eg5, and Eg6 are cladding layers 3 and 6, respectively.
, shows the bandgap energies in the multiple active layer 10, and the bandgap energies increase in this order. Further, in the figure, λC, λ3, λ4, λ5, and λ6 indicate wavelengths corresponding to the bandgap energies in the cladding layers 3 and 6 and the multiple active layer 10, respectively, and the wavelengths are shorter in this order.

Next, the operation will be explained. SLD pn
In the forward direction with respect to the junction, that is, positive to p electrode 8, positive to n electrode 1
When a voltage is applied so as to make it negative, electrons and holes are injected into each active layer in the multiple active layer 10, and spontaneous emission light and stimulated emission light are emitted from the device end face. Here, this emitted light will be explained using the band diagram shown in FIG. 2 as an example. Within the multi-active layer 10, four different bandgap energies Eg3, Eg4, Eg5, E
There are 12 active layers with g6. Here, E
The ratio of the total layer thickness of each active layer with bandgap energies of g3, Eg4, Eg5, and Eg6 is 2:3:4:
Since the multi-active layer 10 has the above-described configuration, its spectrum shape has a single peak and a broad spread centered on λ6 corresponding to the bandgap energy of Eg6.

[0016] Furthermore, the above Eg3, Eg4, Eg5, Eg
The ratio of the total layer thickness of each active layer in multiple active layers with a bandgap energy of 6 is 2:3:4 as above.
:5, Eg3,E as shown in FIG.
A multiple active layer in which the bandgap energies of g4, Eg5, and Eg6 exhibit parabolic regularity is considered, but unlike the multiple active layer 10 described in the above embodiment, electrons and holes are stacked in a band. Since the drop is concentrated in the active layer with the lowest gap energy, it is not possible to obtain a broad broadening in the spectral shape obtained from this SLD having multiple active layers.

As described above, in the above embodiment, the active layer having a bandgap energy corresponding to the apex portion of the spectrum shape having a single peak and broad spread is thick, and the active layer has a bandgap energy corresponding to the apex portion of the spectrum shape having a single peak and broad spread. The active layer with the corresponding bandgap energy becomes thinner in distribution toward the tail.
A multiple active layer 10 formed by laminating two or more active layers having energy is provided between the first and second cladding layers 3 and 6 having a larger band gap energy, and each of the multiple active layers 10 is The active layer is laminated in an irregular order that prevents electrons and holes from concentrating on the active layer with the lowest bandgap energy and falling, resulting in an SLD with a gentle, unimodal spectral shape. can be obtained.

[0018]

As described above, according to the SLD of the present invention, the active layer having bandgap energy corresponding to the apex portion of a spectrum shape with a single peak and broad spread is thick and has The active layer having bandgap energy, which corresponds to each part separated toward the tail, is distributed so that it becomes thinner as it goes toward the tail.
A multiple active layer formed by laminating two or more active layers having various band gap energies is provided between first and second cladding layers having a larger band gap energy, and each of the multiple active layers is The active layer is laminated in an irregular order that prevents electrons and holes from concentrating on the active layer with the lowest bandgap energy and falling, resulting in an SLD with a gentle, unimodal spectral shape. There is an effect that can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a structural sectional view showing the structure of an SLD according to an embodiment of the present invention.

FIG. 2 is a band diagram showing a band diagram of an SLD according to an embodiment of the present invention.

[Figure 3] S with multiple active layers with parabolic regularity
FIG. 3 is a band diagram showing a band diagram of an LD.

FIG. 4 is a structural cross-sectional view showing the structure of a conventional SLD.

FIG. 5 is a top view of a conventional SLD with an n-electrode removed.

FIG. 6 is a band diagram showing a band diagram of a conventional SLD.

FIG. 7 is a waveform diagram showing the spectrum shape of a conventional SLD.

[Explanation of symbols]

1 n-electrode 2 n-type GaAs substrate 3 n-type AlGaAs first cladding layer 4a
First active layer 4b Second active layer 5 Guide layer 6 P-type AlGaAs second cladding layer 7
p-type GaAs contact layer 8p
Electrode 9 Zn diffusion region 10 Multiple active layers

Claims (2)

[Claims] 1. A cladding layer of a first conductivity type disposed on a substrate, a cladding layer of a second conductivity type opposite to the first conductivity type, and an undoped, first or second conductivity layer sandwiched therebetween. a double heterostructure consisting of a type active layer, a first conductivity type contact layer disposed on the second conductivity type cladding layer, and a second conductivity type contact layer disposed on the second conductivity type cladding layer;
a stripe-shaped second conductivity type diffusion region formed reaching the conductivity type cladding layer, and in which a current is injected into the active layer through the diffusion region; The active layer is undoped, first conductivity type, or second conductivity type, and has a bandgap energy corresponding to the apex part of a spectrum shape with a single peak and broad spread. A multilayer structure in which two or more active layers with various band gap energies are laminated so that the active layers with band gap energies corresponding to the parts separated from each other become thinner in distribution toward the bottom. A super luminescent diode characterized by an active layer. 2. The stacking order of each active layer in the multi-active layer is irregular so that electrons and holes do not concentrate and fall in the active layer with the lowest band gap energy. Features a super luminescent diode.