KR860000478B1 - Lasers triode - Google Patents

Abstract

The laser triode comprises net- or line-shaped gate layer in a photo diode. Photomodulation is controlled by voltage drop at gate electrode. The laser triode keeps high speed modulation and high density information.

Description

Laser trio

1 is a vertical cross-sectional structure diagram of a conventional short wavelength AlGaAs / GaAs double heterojunction laser diode.

2 is a vertical cross-sectional structure diagram of a conventional long wavelength InGsAsP / InP double heterojunction laser diode.

3 is an operating characteristic curve of a laser diode.

4 is a relation diagram of modulated light output in the case of pulse modulation using a conventional laser diode.

5 is a vertical cross-sectional view of a short wavelength AlGaAs / GaAs double-heter junction laser triwood according to the present invention.

6 (a) and 6 (b) are operating principle diagrams of the laser trio of FIG.

Figure 7 is a vertical cross-sectional view of another embodiment of a long wavelength InGsAsP / InP double heter junction laser triwood according to the present invention.

8 (a) is a relation diagram of injection current and light output in the case of pulse modulation of a conventional laser diode.

8 (b) is a diagram illustrating a relationship between gate voltage and light output in the case of pulse modulation of the laser trioud of the present invention.

Figure 9 (a) is a relationship diagram between the injection current and the light output in the case of analog modulation of the conventional laser diode.

Figure 9 (b) is the relationship between the gate voltage and the light output in the case of analog modulation of the laser tri-oud of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser triode that can be used as a signal light source for optical communication, and more particularly, to a semiconductor laser triode having a gate inside a conventional laser diode.

Background Art [0002] Conventional light transmission diodes (LEDs) and laser diodes (Laser Diodes) have been used as signal light sources for semiconductor optical communication. However, the light emitting diode as a semiconductor light emitting device used in optical communication has a wide wavelength, so when waveguided by optical fiber, strong power is reduced due to loss in dispersion and coupling with optical fiber. It was not suitable for. Therefore, the use of laser diode as a light emitting device with high monochromaticity, narrow wavelength, high light output, and fast modulation speed is suitable for transmission over medium and long distance medium capacity, and the semiconductor laser diode is used as light communication device for optical communication for the above purpose. come.

FIG. 1 (a) is a vertical cross-sectional structure diagram of a conventional short wavelength AlGaAs / GaAs double-heterojunction laser diode, in which 1 is a P-type Al _z Ga _1-z As layer, and 2 is an n-type or P-type. Al _y Ga _1-y As layers, 3 are n-type Al _z Ga _1-z As layers, 4, n-type GaAs layers, and 5 and 6 are electrodes. In the first (a), the electrode 5 is a stripe electrode, the n-type or P-type Al _y Ga _1-y As layer 2 is an active layer of lazy diode having a thickness of 0.1-0.2 μm, and the P-type Al _Z Ga _{1- The Z} As layer 1 and the n-type Al _Z Ga _1-Z As layer 3 are clad layers each having a thickness of 2-3 μm.

Now putting a positive voltage to the stripe electrodes 5, 6 National assuming going by increasing the injected current by applying a negative voltage form a double hetero potential barrier virus voltage of the laser diode becomes a forward voltage P-type Al _Z Ga _1- Holes and electrons of _Z As 1 and Al _Z Ga _1-Z As layer 2 are injected into the active layer Al _y Ga _1-y As layer 2 and recombined to generate spontaneous emission light. It spreads. Therefore, the natural emission light that is carried out in the reflector direction, which is both ends of the stripe electrode 6 direction, is amplified by the induced emission action and reflected by the reflector and returned. The laser diode starts oscillation when the light amplified by the induced emission action is absorbed by the free carrier in the active layer or is greater than the reflected power consumption on the reflective surface. At this point, the injection current is increased, and the injection current is a threshold current, and a characteristic curve as shown in FIG. 3 is drawn. On the other hand, the band gaps of the cladding layers P-type Al _Z Ga _1-Z As layer 1 and n-type Al _Z Ga _1-Z As layer 3 are n-type or P-type Al _y Ga _1-y As layers as active layers. The refractive indexes of the clad layers P-type Al _Z Ga _1-Z As layer 1 and n-type Al _Z Ga _1-Z As layer 3, which are larger than the band gap of 2, are n-type or P-type Al _y Ga as the active layers. _1-y as layer is less than a refractive index of the second bow seolcheung an n-type or P-type Al _y Ga _1-y as layer 2 as if to play the role which gathers the generated light such as a core (core) optical seomwoo (optical Fiber) While acting as an optical waveguide, the laser light is emitted from the reflecting surface with respect to the injection current above the threshold hold current of the laser diode. In addition, the electrode 6 on the stripe prevents the spread of the injection current and unifies the oscillation mode.

2 is a vertical cross-sectional structure diagram of a conventional long-wavelength InGsAsP / InP double-heter junction riser diode, where 7 is a P-type InP layer, 8 is an n-type or P-type InGsAsP layer, and 9 is an n-type InP Layer, 10 is an n-type InP layer, and 11 and 12 are electrodes. Therefore, the P type InP type 7 and the n type InP layer 9 are clad layers which play the same role as the P type Al _Z Ga _1-Z As layer 1 and n type Al _Z Ga _1-Z As layer 3 shown in FIG. 1 (a). . The electrode 11 serves as a stripe-like electrode and serves the same role as the electrode 6 in FIG. 1 (a). The operating relationship when the positive electrode is applied to the stripe electrode 11 and the negative electrode is applied to the electrode 12 is shown in FIG. The operation of the short-wavelength AlGaAs / GaAs double-herter junction laser diode of a) is the same, the oscillation laser emission wavelength is 0.8-0.9μm for the AlGaAs / GaAs double heterojunction laser diode and 1-1.7μm for the InGsAsP / InP double hetero laser diode. There is only a difference, and with respect to the optical fiber, the light emission wavelength of the InGsAsP / InP dual hetero laser diode has the advantage of low transmission loss.

Therefore, in the optical transmission device using the laser light source as a laser light source as described above, the optical modulation has been performed by installing a laser diode driving circuit and applying a forward voltage to the laser diode to carry a modulation current to the injection current. . In particular, in case of analog modulation, the current above the threshold current is used as the bias current operating point of the laser diode, and the modulation is directly modulated by the change of injection oil. In the case of the pulse modulation, the operating point is below the threshold current. And modulate the injection current by the pulse signal.

4 is a modulation light output relation diagram in the case of pulse modulation using a conventional laser diode. The conventional laser diode is a modulation method for changing the injection current with respect to the forward bias of the diode. Therefore, in the case of pulse modulation, the operating point is described below the threshold current and pulse modulation has been performed by flowing the modulation current to the positive electrode of the reactor diode. Therefore, the carrier accumulation effect due to the life time of the carrier injected into the active layer of the laser diode. Due to the pattern effect, the high-density information signal cannot be modulated. Thus, the negative effect is suppressed by flowing a negative pulse as shown in FIG. 4A to obtain a carrier density in the active layer of the laser diode as shown in FIG. The pulse modulation is obtained as shown in FIG.

In the case of the optical modulation by the conventional laser diode as described above, the accumulation carrier is generated by the life time of the carrier injected into the active layer by the direct modulation method of changing the injection current, thereby generating a pattern effect. Such a pattern effect can cause high-speed modulation of GH _{x when} biasing a point above the threshold current as an operating point, but the waveform distortion becomes severe. However, when biasing the operating point below the threshold current, the pattern effect is reduced but the modulation speed is decreased. Therefore, the pattern effect using the conventional laser diode results in a severely impaired unit information signal density per hour, and has a drawback that a high density information signal due to high speed modulation cannot be obtained.

In addition, in the conventional laser diode, there is a drawback that a high capacity converter or an element must be used to modulate an information signal using a driving current.

Accordingly, an object of the present invention is to provide a laser triode having an information signal adjusting gate inside the laser diode.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 5 is a vertical sectional view of a short wavelength AlGaAs / GaAs double heterojunction laser trioud according to the present invention, in which FIG. 13 is a P-type Al _Z Ga _1-Z As layer 14 is an n-type or P-type Al _y Ga _1-y As As an active layer, 15 is an n-type Al _Z Ga _1-Z As layer, 16 is an n-type GaAs layer, 17 is a rod or mesh-like gate layer, 17a is a gate electrode drawn from the gate layer 17, and 18 is An electrode for applying a positive voltage and 19 is an electrode for applying a negative voltage. The gate layer 18 of the second layer rod or mesh is formed by forming a p-type impurity layer on the n-type GaAs layer 16 in the form of a rod or a mesh, and the gate layer 18 and the n-type GaAs layer 16 form a pn junction, and then brate down. It is formed for the purpose of using deflation formation by supplying voltage until break down occurs.

Hereinafter, the operation relationship of the short wavelength AlGaAs / GaAs double heterojunction laser trioud of FIG. 5 will be described with reference to FIGS. 6 (a) and 6 (b). FIG. 6 (a) is an operation principle diagram before supplying the gate signal, where 20 is laser light emitted from the laser diode, and other numbers are the same as those shown in FIG. FIG. 6 (b) shows an operation principle after supplying a positive gate signal. In FIG. 21, a deflection layer is shown, and the remaining numbers are the same as the display numbers in FIG.

A positive voltage is applied to electrode 18, a negative voltage is applied to electrode 19, and a forward bias is applied. As shown in FIG. 6 (a), when there is no gate signal supply to gate electrode 17a, the clad layer P-type Al _Z Ga _1-Z The electrons of the n-type Al _Z Ga _1-Z As layer 15 and the n-type GaAs layer 17, which are the holes of the As layer 13 and the cladding layer of the N layer, are injected into the Al _y Ga _1-y As layer 14, which is the active layer, and recombine. It is the same as the operation of the conventional short wavelength AlGaAs / GaAs heterojunction laser diode of FIG. 1 described above, which emits and emits laser light 20 through the active layer by amplification by induced emission.

Meanwhile, a positive voltage to the electrode 18 is applied to electrode 19 has a when the active layer is a negative voltage and to make a bias in the forward direction to the laser diode as help claim 6 (b) to flow in the drain sh huldeu current over injection current Al _y Ga _The laser light is emitted from the _1-y As layer 14. At this time, if a positive gate signal is supplied through the gate electrode 17a, a deflection layer 21 is formed around the gate layer 17 of the P-shaped rod or mesh as shown in FIG. 6 (b). In the N layer composed of the type Al _Z Ga _1-Z As layer 15 and the n type GaAs layer 17, the electrons injected into the n-type or P-type Al _y Ga _1-y As layer 14 which are active layers are controlled. The deflection layer 21 is further strengthened with respect to the positively input high-voltage supply signal, thereby blocking the flow of injected electrons to completely block the current flowing through the electrode 19 to stop lasing with the laser trioud. do. At this time, the maximum allowable value of the gate supply voltage is before the breakdown voltage between the N-type layer and the gate layer, and the design can be adjusted by the distance between the gate and the gate and the size of the gate layer.

7 is a vertical cross-sectional view of a long wavelength InGsAsP / InP double heterojunction laser triwood according to the present invention, in which 22 is a P-type InP layer 23 is an active layer, and an InGsAsP layer 24, 25 is an n-type InP layer 26 is a gate of FIG. The gate layer 26a on the same bar or mesh as the layer 17 is a gate electrode drawn from the gate layer 26, 27 is an electrode for applying a negative voltage, and 28 is an electrode for applying a positive voltage.

The operation relationship of the long wavelength InGsAsP / InP double heterojunction laser trioud of FIG. 7 is the same as the operation of the short wavelength AlGaAs / GaAs double heterojunction laser trioud of FIG.

8 (a) is a relationship between the modulation injection current waveform and the optical output of the conventional laser diode in the case of pulse modulation, Figure 8 (b) is a gate voltage and modulation of the laser trioud according to the present invention in the case of pulse modulation This is a relation diagram of light output.

As described above, in the case of pulse modulation, the conventional laser diode modulates the operating point below the threshold current point, thereby obtaining positive modulated light output as in the case of FIG. You get the output. However, in the case of the laser triwood according to the present invention, the light output with respect to the gate voltage as shown in FIG. 8 (b) is negative. This is due to the phenomenon that the flow of electrons injected from the electrode into the active layer is suppressed when the end point is set to the lasing state and a positive voltage is applied to the gate electrode as described above.

9 is an optical output relation diagram in the case of analog modulation, and FIG. 9 (a) is a relation diagram of a modulation injection current and a corresponding light output in a conventional laser diode. FIG. 9 (b) is a laser diagram according to the present invention. The relationship between the modulation gate voltage and the corresponding light output in the case of the trioud is the same for setting the operating point to the lasing state in both cases. However, as described above, the light output is positive in the case of the conventional laser diode and negative in the case of the laser trioud according to the present invention. Therefore, in the conventional laser diode, the operating point is set at a position below the threshold current and pulse modulation is performed. In the case of the laser trioud according to the present invention, the operating point is raised at a position above the threshold current. In this state, the modulation speed becomes high because pulse modulation is performed by changing the gate voltage.

In addition, in the case of the conventional laser diode, since the current modulation method changes the injection current, in order to reduce the pattern effect caused by the accumulation carrier, a method of adding a negative pulse to the positive pulse has to be selected. In the case of the laser triode according to the present invention, the pulse voltage is modulated by applying the gate voltage as a positive voltage, so that there is no pattern effect, and the high-speed modulation and the high-density information processing are possible.

On the other hand, in the case of the conventional laser diode, since the laser diode driving circuit should be installed because the injection current is used as the modulation current, the driving circuit should use a high capacity converter. Since only a volt voltage is required, it is possible to directly modulate and drive the laser trioud as a low-capacitance signal, which reduces the manufacturing cost of the system and has the advantage of enabling the IC of an optical communication integrated circuit.

Claims (1)

In compound semiconductor optical communication light emitting diode diode using Group 2, 3, 5, 6 element, the gate electrodes 17a and 26a are provided inside the light emitting diode diode by adjusting the gate layers 17 and 26 for adjusting the information signal of a mesh or thin object. Laser triode characterized by light modulation by voltage change of

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