JP2769053B2 - Super luminescent diode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super luminescent diode (hereinafter referred to as "SLD"), and more particularly to an SLD having a single peak and a broad spectrum of spontaneous emission light.

[0002]

2. Description of the Related Art In recent years, attention has been paid to an SLD which is positioned between a semiconductor laser and a light emitting diode. This light emitting device has a broad spectrum spread like a light emitting diode, and is capable of emitting light having an output as high as a semiconductor laser. Therefore, the SLD has an advantage that it can extract high-output, incoherent light with good directivity. Taking advantage of this advantage, it is being used as a light source for a fiber gyro or the like, which is a component of an inertial navigation device for acquiring instantaneous position information of an aircraft or a ship and guiding it to a destination.

The point of the structure and manufacturing of the SLD is how to suppress laser oscillation, widen the spectrum width of spontaneous emission light, and increase its light output.

FIG. 4 is a cross-sectional view showing a basic structure of a conventional SLD. In FIG.
an aAs substrate, 3 an n-type AlGaAs first cladding layer,
4a is a first active layer and 4b is a second active layer.
The two active layers 4a, 4b have slightly different band gap energies. 5 is the two active layers 4
a, 4b, and a band gap higher than them.
A guide layer having energy, 6 is a p-type AlGaAs second cladding layer, 7 is an n-type GaAs layer, 8 is a p-electrode, 9
Is a Zn diffusion region.

FIG. 5 is a top view in which the n-electrode is removed from the conventional SLD shown in FIG. 4. In the figure, when viewed from above, the Zn diffusion region 9 is not parallel to the resonator direction but has a certain angle. It can be seen that it is tilted, but this is to suppress laser oscillation. Further, the laser oscillation is suppressed by setting the reflectivity at the laser end surface to 3% on the front surface and 3% on the rear surface.

FIG. 6 shows a band diagram of the conventional SLD shown in FIG. In the figure, E _gC , E _gG ,
E _g1 and E _g2 are the first and second cladding layers 3 and 6, respectively.
The band gap energy of the guide layer 5, the first active layer 4a, and the second active layer 4b is shown, and the band gap energy is larger in this order. Λ _C , λ _G ,
λ ₁ and λ ₂ are the first and second cladding layers 3 and 6, respectively.
The wavelength corresponding to the band gap energy of the guide layer 5, the first active layer 4a, and the second active layer 4b is shown, and the wavelength is shorter in this order.

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

FIG. 7 is a view showing the spectrum shapes of the emitted spontaneous emission light and stimulated emission light, corresponding to the band diagram of FIG. 6. In FIG. 7, the bandgap energy E _g1 is changed from the first active layer 4a to the band gap energy E _g1 . Corresponding center wavelength λ ₁
Are emitted from the second active layer 4b as spontaneous emission light and stimulated emission light having a center wavelength λ ₂ corresponding to the bandgap energy E _g2 , and each has a combined spectral shape. You can see that there is. As described above, since the two spontaneous emission light and the stimulated emission light are added, the spectrum has a broader spectrum than the spectrum of the spontaneous emission light and the stimulated emission light from one active layer.

[0009]

Since the conventional SLD is configured as described above, the spectral shape is wide, but the light condensing property of the lens is poor because it is not a smooth single peak but a double peak. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to obtain an SLD having a gentle, single-peak, wide spectrum shape.

[0011]

An SLD according to the present invention
Has a bandgap energy corresponding to the peak at the top of a single-peak, broad-spread spectrum shape, and the active layer has a bandgap energy corresponding to each part away from the peak toward the bottom. The active layer is formed by laminating two or more active layers having various band gap energies so that the distribution becomes thinner toward the bottom. The order of lamination of the active layers in the multiple active layer, which is provided between the second clad layers, is such that electrons and holes are not concentrated in the active layer having the lowest bandgap energy. It is what it was.

[0012]

According to the present invention, a peak corresponding to a single-peaked broad spectrum shape is obtained.
The active layer having the bandgap energy is thick, and the active layer having the bandgap energy corresponding to each portion away from the top toward the hem has various distributions such that the distribution becomes thinner toward the hem. A multi-active layer formed by laminating two or more active layers having energy is provided between the first and second cladding layers having a larger bandgap energy, and a stacking order of each active layer in the multi-active layer is provided. Are arranged in an irregular order such that electrons and holes do not concentrate and fall into the active layer having the lowest band gap energy, so that an SLD having a smooth and single-peaked spectral shape can be obtained. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing the front of an SLD according to an embodiment of the present invention. In FIG. 1, reference numeral 10 denotes an activity having a bandgap energy corresponding to a vertex in a single-peak broad-spectrum spectral shape. The layer is thick, and the active layer having a band gap energy corresponding to each portion away from the apex toward the foot has two or more layers having various band gap energies such that the distribution becomes thinner toward the foot. An active layer is formed by stacking active layers. The order of stacking the active layers in the multiple active layer 10 is such that electrons and holes do not concentrate on the active layer having the lowest bandgap energy. The order is irregular. In this example, the active layer is composed of a total of 12 active layers. As shown in FIG. 5 of the conventional example, when viewed from above, the Zn diffusion region 9 is not parallel to the cavity direction but inclined at a certain angle to suppress laser oscillation. Other parts are the same as or similar to those of the related art.

FIG. 2 is a band diagram of the SLD of this embodiment shown in FIG. In the figure, E _gC , E _g3 , E
_g4, E _g5, E _g6 each cladding layers 3 and 6, shows the band gap energy of the multiple active layer 10,
The band gap energy is larger in this order. In the figure, λ _C , λ ₃ , λ ₄ , λ ₅ , and λ ₆ indicate wavelengths corresponding to the band gap energies in the cladding layers 3 and 6 and the multiple active layers 10, respectively, and the wavelengths are shorter in this order.

Next, the operation will be described. SLD pn
In the forward direction with respect to the junction, that is, the p electrode 8 is positive, the n electrode 1
When a voltage is applied so as to be 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 end face of the element. Here, the emitted light will be described using the band diagram shown in FIG. 2 as an example. Within the multi-active layer 10, there are twelve active layers with four different bandgap energies E _g3 , E _g4 , E _g5 and E _g6 . Where E _g3 ,
The ratio of the total layer thickness of each active layer having the band gap energies of E _g4 , E _g5 , and E _g6 is 2: 3: 4: 5, and the multiple active layer 10 has the above-described configuration. Therefore, its spectral shape has a single peak and broad spread around λ ₆ corresponding to the band gap energy of E _g6 .

The ratio of the total thickness of each active layer in the multiple active layers having the band gap energies of E _g3 , E _g4 , E _g5 , and E _g6 is 2: 3: 4: 5 as in the above. Some examples include E _g3 , E _g4 , E _g5 ,
A multi-active layer in which the band gap energy of E _g6 indicates a parabolic regular stack is conceivable. However, unlike the multi-active layer 10 described in the above embodiment, electrons and holes have band gap energies. , The spectral shape obtained from the SLD having the multiple active layers cannot have a broad spread.

As described above, in the above embodiment, the active layer having the bandgap energy corresponding to the peak portion in the spectrum shape having a single peak and broad spread is thick, and the active layer having the band gap energy corresponding to the peak portion is separated from the peak portion toward the bottom. The active layer having the corresponding band gap energy has various band gaps so that the distribution becomes thinner toward the bottom.
A multi-active layer 10 formed by laminating two or more active layers having high energy is provided in the first and second cladding layers 3 and 6 having a larger bandgap energy. Since the stacking order of the active layers is irregular, so that electrons and holes do not concentrate and fall into the active layer with the lowest bandgap energy, the SLD has a smooth and single-peaked spectral shape. Can be obtained.

[0018]

As described above, according to the SLD of the present invention, the active layer having the bandgap energy corresponding to the apex portion of the spectrum shape having a single peak and a broad spread is thick, and The active layer having the band gap energy corresponding to each part separated toward the skirt has a thin distribution toward the skirt,
A multiple active layer formed by laminating two or more active layers having various band gap energies is provided between the first and second cladding layers having a larger band gap energy, and each of the multiple active layers is Since the stacking order of the active layers is irregular, so that electrons and holes do not concentrate and fall into the active layer with the lowest bandgap energy, the SLD has a smooth and single-peaked spectral shape. There is an effect that can be obtained.

[Brief description of the drawings]

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 an SLD band diagram according to an embodiment of the present invention.

FIG. 3 shows S having a parabolic regular active layer.
FIG. 3 is a band diagram showing an LD band diagram.

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

FIG. 5 is a top view in which an n-electrode is removed from a conventional SLD.

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

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

[Explanation of symbols]

 Reference Signs List 1 n electrode 2 n-type GaAs substrate 3 n-type AlGaAs first cladding layer 4 a first active layer 4 b second active layer 5 guide layer 6 p-type AlGaAs second cladding layer 7 p-type GaAs contact layer 8 p-electrode 9 Zn Diffusion area 10 Multiple active layers

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 33/00

Claims (2)

(57) [Claims] 1. A first conductive type clad layer disposed on a substrate, a second conductive type clad layer opposite to the first conductive type, and an undoped, first or second conductive layer sandwiched therebetween. A double hetero structure comprising an active layer of a first conductivity type, a contact layer of a first conductivity type disposed on the cladding layer of the second conductivity type, and a cladding layer of the second conductivity type in the first conductivity type contact layer. The second stripe
And a conductive type diffusion region, wherein a current is injected into the active layer through the diffusion region.
In the diode, the active layer is undoped,
The active layer having the bandgap energy, which is of the conductivity type or the second conductivity type and corresponds to the peak portion in the spectrum shape having a single peak and broad spread, is thick,
Two or more active layers having various band gap energies are stacked so that the active layer having the band gap energy corresponding to each portion away from the top to the hem has a thin distribution toward the hem. A super luminescent layer, characterized in that the
diode. 2. The lamination order of each active layer in the multiple active layer is an irregular order such that electrons and holes do not concentrate and fall into the active layer having the lowest bandgap energy. Features a super luminescent diode.