JPS59168683A - Optical semiconductor element - Google Patents

Abstract

PURPOSE:To enable an optical output level to be directly controlled by a single element corresponding to an optical input regardless of laser oscillated beams or naturally emitted light by a method wherein semiconductor layers with specific band gap energy Eg comprising semiconductor layers with Eg=Eg3 as main light emitting layers and other semiconductor layers with Eg=Eg4 as main light absorbing layers are formed. CONSTITUTION:When this optical semiconductor element is supplied with current in normal direction, firstly electron - hole are recoupled in the fifth P type InGaAsP layer 26. Due to lower P concentration in the second, third and fourth P type InGaAsP layers 23, 24 and 25, the barrier against the fifth P type InGaAsP layer 26 is lowered. Therefore leak current is increased corresponding to increased current resultantly increasing the electrons running into the first P type InGaAsP layer 22 to increase optical output with wave length of 1.3mum very rapidly. At this time, if optical output with wave length of 1.06mum is entered through a window, it is absorbed into the third P type InGaAsP layer 24 to form hole - electron. Corresponding to increased intensity of the entered light, the hole concentration in the third P type InGaAsP layer 24 is increased making hole Fermi level approach to valence band raising barrier against the electron of the fifth P type InGaAsP layer 26.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical semiconductor device having different optical output levels depending on optical input. Elements that control optical output according to optical input will become increasingly important in the future in order to perform functions such as optical modulation and optical calculation in systems that transmit multiple information through optical signals. Conventionally, a photodetector element is used to control the light output depending on the light input.

Generally, a method was used in which individual elements such as an electric circuit and a light emitting element were combined to convert an optical signal into an electric signal, and then the sickle was converted back into an optical signal. Furthermore, as devices that do not perform optical-electrical conversion, optical bistable semiconductor lasers with non-uniform current distribution are currently under research. However, it is a combination of individual elements, and a simple light emitting diode (LE
It is not necessarily effective for light emission (referred to as D).

The present invention makes it possible to realize, with a single optical semiconductor element, the function of controlling the light output regardless of whether it is a laser light or natural light emission K depending on the light input.

That is, in an optical semiconductor element made of a compound semiconductor, at least the first conductive type has a band gap energy (
(hereinafter referred to as Eg) is a semiconductor layer with Eg=Egt and a first
Or, in the second conductivity type, Eg""ggs (Egs<Egt
) and a semiconductor layer of the second conductivity type, Eg””EgIl (E
gs > Ego ) and a semiconductor layer with low carrier concentration;
'In the second conductivity type, Eg=Eg4 (Egt>EgJ and a semiconductor layer with low carrier concentration, and in the second conductivity type, Eg=Eg
s (Egs > Egs ) and a semiconductor layer with low carrier concentration, and the second conductivity type, Eg = Ega (Ege < Egs).
Eg=Egy(Egy
>Ego) semiconductor layers are formed in order, and the above Eg"Eg
This is an optical semiconductor element characterized in that it has a structure in which the semiconductor layer a is a main light emitting layer and the semiconductor layer Eg""Egt is a main light absorbing layer.

The present invention will be explained in detail below using the drawings.

FIG. 1 shows a preliminary energy band diagram for explaining the operating principle of the optical semiconductor device of the present invention. N-type semiconductor layer 11 with band gap energy Eg""Egt, P-type semiconductor layer 12 with Eg"Egi (Egs<Egt), low concentration P-type semiconductor layer 13 with Eg""Egs (Egs>Egs), Eg=Eg4 (Eg4>Egs)
low concentration P-type semiconductor/Q14, Eg=Egs(Egr,
>Egg) low concentration P-type semiconductor layer 15, Eg=Ega
(Egs<Egt) P-type semiconductor layer 16, and Eg=
P-type semiconductor layers 17 of Egt (Eg7>Egg) are formed in this order. Here, the bandgap energy Eg8 of the semiconductor layer 16 is adjusted to the wavelength λout of the light to be output. Further, the bandgap energy E g 4 of the semiconductor layer 14 is adjusted to the wavelength λin of the input light. Figures 1 (a) and (b) are both with a forward current flowing through the device, (a) is when there is no optical input, and (b) is when there is no optical input.
) indicates the case with optical input.

First, the case where there is no optical input will be described. When a current is passed through the device in the forward direction, electrons and holes first recombine in the semiconductor layer 12. When the current is further increased, the electron Fermi level of the semiconductor layer 12 increases, and the electron leakage current flowing across the heterobarrier with the semiconductor layer 13 gradually increases. Some of the electrons that have crossed this heterobarrier are in the semiconductor layers 13 and 1.
4.15, the remaining particles reach the semiconductor layer 16, where they recombine with the holes and increase the energy Egg (i length λ
out ) light is emitted. The intensity of this light increases rapidly as the current increases, as shown by the broken line in FIG.

Next, the case where there is optical input will be described. Wavelength λ (λ〈
When light of
4 and generates holes-electrons. Since the P# degree of the semiconductor layer 14 is low, the hole Fermi level of the semiconductor layer 14 is 200 to 3 from the valence band when there is no optical input.
00meV It is within the forbidden band. However, when the hole concentration in the semiconductor layer 14 increases due to the incidence of light, the hole Fermi level approaches the valence band, and as a result, the conduction band of the semiconductor layer 14 increases as shown in FIG. 1(b). Rise.

Therefore, the barrier of the semiconductor layer 12 to electrons becomes high. Depending on the intensity of the incident light, the height of the barrier is 100~
200 m e V change. Barrier height is 100~
When the temperature rises to 200 meV, the leakage current increases to 1. /i.

-Decreased to V100. Therefore, when the incident light intensity is high, even if the current flowing through the element is increased, the leakage current flowing across the heterobarrier is significantly suppressed.
The optical output of out hardly increases as shown by the solid line in FIG. In this way, the current-light output characteristics of the device vary greatly depending on the presence or absence of light input. Therefore, when the current value is held constant and the optical input level is changed, the optical output changes as shown in FIG. 3, with a low optical input resulting in a high optical output and a high optical input resulting in a low optical output. The above is an outline of the operating principle of the present invention.

Note that the carrier concentration of the low carrier concentration semiconductor layer is 18 t.
s or more, the above-mentioned actions and effects cannot be expected. l
The effect appears at Q ``Cm-'' range, and becomes noticeable when the temperature is below 1017α-3.

Next, the present invention will be described in more detail with reference to Examples.

Fig. 4 (al indicates the cross-sectional structure of an optical semiconductor device according to an embodiment of the present invention. Fig. 4 indicates an energy band diagram. The embodiment of Fig. 4 shows spontaneous luminescence (LED output). This is an example of controlling.

A first P-type InGaAsP layer 2 is formed on a P-type "■" substrate 21.
2 (Eg:=0.95eV, P ~5X1017cM
-3. thickness 1 pm) + second P q InGaAs
P JCn 23 (Eg=1.15eV, PH1X
10 "α', thickness 1 μm), third P glass InGa
AsP layer 24 (Eg=1.10eV, P~lXl0"
z-', thickness 0.5ttyn), fourth P-type InG
aAsP layer 25 (Eg=1.15eV, Pi6X1
0 "as-', thickness o, 2 pm) *Fifth P type I
nGaAsP Mj 26 (Eg=1.0OeV, P
~5X1017α-3, thickness o2pm), n-type In
P layer 27 (Eg=1.34eV, n~2X1
018 cm-' and a thickness of 2 μyn) are continuously formed by liquid phase epitaxial method. n-type InP layer 270
CVD [S+0. After forming the film 28, a pattern of 20 to 40 μm in diameter is formed using photoresist.
S10. remove. Next, SIO, film 2
8 and n-type InP 27 and heat-treated in an H or N2 atmosphere to form an n-type ohmic electrode 29. Next, the P-type InP substrate 21 is polished to a thickness of about 100 μm. A on the P-type InP substrate 21
After depositing uZn, pn-type InP is formed using photoresist.
According to the leakage of the 5in2 film 28 on the surface of 27,
A circular pattern with a diameter of about 120 μm is formed on the uZn film, and the window 31 is formed by removing the AuZn film-af in a circular shape. Finally, a P-type ohmic electrode 30 is formed by heat treatment in N9 or N.

When a current is passed in the forward direction through this optical semiconductor element, electron-hole recombination occurs first in the fifth P-type InGaAsP layer 26. Second. third and fourth P-type InGaAsP layers 23,
Since the P concentration of 24 and 25 is low on the order of 10161-3, the barrier to electrons of the fifth P-InGaAsP7M26 is low at about 100 meV, and when the current is increased, the leakage current increases, and as a result, the first P-InGaAsP7M26 Type I
The number of electrons flowing into the IIG aA s P layer 22 increases, and the optical output at a wavelength of 13 μ2n increases rapidly. Here, wavelength 1.
When light of 06μ〃J is incident through the window, the third P type I n
It is absorbed by the GaAsP layer 24 and generates holes and electrons. While increasing the incident light intensity, the third P-type InGaAs
The hole concentration in the P layer 24 increases, the hole Fermi level approaches the valence, and the barrier to electrons of the fifth P-type InGaAgP#26 increases by about 100 to 200 meV. As a result, the leakage current gradually decreases, and the optical output at a wavelength of 13 μm decreases as shown in FIG. In this way, according to this embodiment, it was possible to directly control the LED output light according to the level of multiple input lights. Note that a structure for inputting and outputting light from the example of the n-InP layer 27 has a similar light control function, but
In this case, there is an advantage that the input source effectively enters the P-type InGaAsP layer 24. FIG. 6 is a diagram showing another embodiment of the present invention. The embodiment shown in Fig. 6 is the same as the embodiment shown in Fig. 4.
It has the function of controlling four to nine laser oscillation lights. S10, which is different from the example in FIG. The film 28 is removed in a stripe shape with a width of about several μη1, and the first P-type InG aA
The thickness of the sP layer 22 is approximately 0.2 pm. As shown in FIG. 7, when there is no input light, the leakage current is large and the oscillation threshold is low; when the input light is strengthened, the leakage current decreases significantly and the oscillation threshold becomes high.

Therefore, if the input light intensity is changed while keeping the current constant, the 8th
As shown in the figure, the output light intensity changes greatly. According to this embodiment, the laser oscillation output could be directly controlled according to the optical input level. In the example of FIG. 6, the first, second and third P-type InGaA gP layers 22 , 23 , 2
4 is provided over the entire surface of the element, the same light control function can be achieved even if it is provided only in a portion in the direction of the resonator. In this case, the output light can be controlled with a much smaller optical input level.

In the above embodiment, the emission wavelength is 1.3 μm and the human power wavelength is 1.
Although the case of 0.06 μm has been shown, the present invention can be applied to other wavelengths by changing the Eg, carrier concentration, and thickness of each layer.

Further, the present invention can also be applied to devices using other compound semiconductors such as GaAg/A (GaAs). Furthermore, the present invention can also be applied when the electrical conductivity types of each layer are reversed.

As described above in detail, the present invention makes it possible to obtain an optical semiconductor device that can directly control the optical output level depending on the optical input, regardless of whether it is laser oscillation light or natural light emission, using a single device. did it.

[Brief explanation of drawings]

Figures 1, 2, and 3 illustrate the operating principle of the present invention, Figures 4 and 5 illustrate the first embodiment of the present invention, and Figures 6, 7,
FIG. 8 is a diagram showing a second embodiment of the present invention. In the figure, 11.27 is the first conductivity type semiconductor layer of E g ``E g t, 12.26 is the first conductivity type semiconductor layer of Eg'''Egs, and 13゜25 is the second conductivity type semiconductor layer of Eg = E g s. 14.24 is a second conductivity type semiconductor layer of Eg""Eg4, 15.23 is a second conductivity type semiconductor layer of Eg"Eg5, and 16.22 is a second conductivity type of Eg-Ega. Semiconductor layer 17.21 indicates the second conductivity type semiconductor layer of E gJ gγ. FIG. 1(a) /7j '6 j15j/4j/3jlZj //FIG. Also (θ, (1) Fig. 3 OI 2 3 Optical input ((1, u) Toshi 5 Fig. 0 1 2 3 Optical input (a, u) ni h Otsu Fig. 9 Fig. 7 Ol 2 3 Nishii milk C (1, u) Fig. 0 1 2 3 optical input ((1
,u)

Claims (1)

[Claims] In an optical semiconductor device made of a compound semiconductor, at least the first conductivity type has a band gap energy (hereinafter E
g) is a semiconductor of E g=E g t>Egg)
and a semiconductor layer with a low carrier concentration and a second conductivity type of Eg.
”=Egi (Ega>Egs+) and a semiconductor layer with low carrier concentration, and the second conductive type, Eg”Egs(Egs
g b > E g s ) and a semiconductor layer with a low carrier concentration, and a semiconductor layer of the second conductivity type with Eg""Ega (, Ega
<Egs) semiconductor layer and the second conductivity type, Eg"=Egy
Semiconductor layers of (Egy>Ega) are formed in order, the semiconductor layer of Eg"Ega is the main light emitting layer, and the semiconductor layer of Eg=Eg4 is the main light absorption layer. Features of optical semiconductor devices.