JPS60128690A - Semiconductor light-emitting device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor light-emitting device, a radiant wavelength thereof is stabilized and which has extremely high coherency, by forming a quantum well layer, in which the thickness of an active layer in the semiconductor light-emitting device is smaller than the de.Broglie wavelength of electrons, and forming an active layer as one layer or a plurality of active layers through a barrier layer. CONSTITUTION:When a semiconductor light-emitting device has a single quantum well layer, a diffraction grating is formed on the interface between an N type lnP confinement layer 12 and an InGaAsP guide layer 13. These each InGaAsP four-element layer is composed of the guide layer 13 in a luminescence wavelength such as 1.30mum, an active layer 14 in one such as 1.53mum and a contact layer 16 in one such as 1.30mum, and the guide layer 13 is brought to a value such as 20nm and the active layer 14 to a value such as 10nm in their thickness. The period of a diffraction grating on the interface between the confinement layer 12 and the guide layer 13 is brought to 480mum, and beams having 1.55mum wavelength by transition between quantum units E1 and Ehh1 are selected. When the semiconductor light-emitting device has multilayers, three layers of the InGaAsP active layers 14 are formed, InGaAsP barrier layers 15 are inserted among the layers 14, and others are executed in the same manner as said single quantum well layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a semiconductor light emitting device which has wavelength stability of 2% and extremely high coherence zoi.

(1)) Background of Technology In optical communications and other systems that use light as a medium for information signals, semiconductor light emitting devices play an extremely important role as light sources that generate optical signals.

Therefore, the realization of the wavelength band required for semiconductor light emitting devices, especially lasers, stable single fundamental zero-order transverse mode oscillation, single longitudinal mode oscillation, reduction of threshold current, improvement of linearity of current-light output characteristics, Many efforts have been made to improve these properties, such as reducing the temperature dependence of these properties.

(C) Conventional technology and problems Many of the semiconductor light emitting devices are conventional.

The active layer is a semiconductor layer with an A-Lugie bandgap corresponding to the target wavelength of light.

By sandwiching the active layer between a pair of semiconductor layers with a higher energy band gap, electrons and holes injected into the active layer are confined and light is emitted.3.This structure In the semiconductor light emitting device of Therefore, the distribution of the energy of light radiated by the transition, that is, the wavelength, becomes wider.In Figure 1, the vertical axis is the energy band axis, the density of state g, and the 2-curve E is the electron 2-curve) lh.
is the heavy hole 9 curve Ht represents the state density of light holes. In most semiconductor lasers, a C-Fapley bellows resonator is provided by a pair of labor planes perpendicular to the active layer, etc., and the inside of the resonant system is C laser oscillation occurs when the C gain and loss are balanced in the vicinity of the wavelength having the maximum gain. In this state, the standing wave between the reciprocal edges is 1. The mode order of the CK mote is as large as 20008 degrees, for example, and the oscillation wavelength changes easily due to changes in temperature and energy band gas, making it impossible to stably control the oscillation wavelength. bad.

In distributed feedback lasers, in which the resonator of the semiconductor laser is selectively feedback-backed using a diffraction grating provided at the interface of the optical waveguide, the controllability of the longitudinal heptad has been greatly improved, and the temperature dependence of the oscillation wavelength has been improved. Also, the state density distribution of electrons and holes decreases due to a temperature change different from the above example.
A shift in the diffraction wavelength occurs, and the temperature range at which a stable single wavelength can be obtained is narrow, and in the above example, due to the reflective surface, the transverse mode automatically becomes the TE mode,
While the fundamental zero-order transverse mode TEO is easily obtained, 9
In distributed feedback lasers, TE mode, TM7-1・
Since this control is not performed, there are problems with matching with external light pollution wave paths, and the coherence is also poor.

If the originality of the active layer of a half-metallic laser is made to be less than the Debrowie wavelength of the carriers, the motion of the carriers in the thickness direction will be quantized. The active layer in this structure behaves as a quantum mechanical well-shaped potential and is called a quantum well layer. The active region of a Kimiko well semiconductor laser may be composed of a single quantum well layer, or may be composed of multiple quantum well layers and barrier layers.

The density of states of carriers in the two-dimensional state quantized by one in this manner becomes step-like as shown in FIG. In this case, the selection for the radiation trend is Δn=Q.For example, the electron of El is 1) combined with the hole of l;1th, or E Ib. Therefore, the wavelength of the light emitted from this quantum well semiconductor laser is not a continuous value, but 1.1', 2, and 2' in Figure 2.
The result is a discrete value corresponding to the engineering energy as shown in .

However, when the resonator of a quantum well semiconductor laser is of the 7Avry-Bello type, it is impossible to control which of the discrete values the laser oscillates at, and the stability of the two oscillation wavelengths cannot be controlled. And coherency is improved compared to the conventional side, but it is still not sufficient.

In order to further improve the quality of optical communication, for example, it is hoped that a homodyne heterotine detection method will become possible by adding an element of light wave incoherence to the current on/off digital communication method, and semiconductor laser light requires a stable coherent lens.

(dl Purpose of the Invention The present invention improves the above situation, stabilizes the radiation wavelength, and achieves extremely high C
An object of the present invention is to provide a semiconductor light emitting device with high coherency.

fe) Structure of the Invention The object of the present invention is to use a semiconductor layer having a thickness equal to or less than the Doe-Browie wavelength of an electron wave as an active layer, and in the vicinity of the active layer,
This is achieved by a semiconductor light emitting device comprising a periodic structure that selectively returns light generated within the active layer.

That is, the active layer of the semiconductor light emitting device of the present invention has a thickness equal to or less than the Doe-Browie wavelength of electrons and is a quantum well layer, and a single active layer or a plurality of active layers are provided with a barrier layer interposed therebetween. It will be done. Normally, a guide layer is provided in contact with one surface of this active layer or a group of active layers, and the A/Rukivant cap is larger than the active layer and smaller than the confinement layer, and the interface between the guide layer and the confinement layer is provided with a guide layer that is in contact with one side of the active layer or group of active layers. A periodic structure 2, typically a diffraction grating, is provided for selectively returning the light produced.

The active layer of the semiconductor light emitting device of the present invention generates light of discrete wavelengths as described above. Laser oscillation is performed at the selected wavelength by feeding back the light using a periodic structure diffraction grating that has a selective effect on light at a desired wavelength among the plurality of wavelengths.

(f) Embodiments of the Invention The present invention will be specifically described below by way of embodiments with reference to the drawings.

Figure 3 (al and (b) shows a single indicator well 1W-f M
FIG. 3 is a cross-sectional view of an embodiment of the present invention taken along sections parallel and perpendicular to the stripes.

In the figure, U, 11 is an n-type indium-phosphorous (InP) substrate, 12 is an n-type 1nP confinement cap, 13 is an n-type indium-potassium-arsenic-phosphorus (lnGaAsP) kite layer,
14 is an InGaASP active layer, 16 is a ■) type Lnl) confinement layer, 17 is a p-type 111P layer, 18 is an n-type InP layer, 19 is a p-type InQaAsP layer, 20 and Q and 21 are electrodes, as shown in Figure 2. Like n-type 1nP confinement layers 12 and 11
A diffraction grating is formed at the interface with the 1 G a ASP guide layer 13 .

In the case of non-implementation, each of the InGaAsP quaternary layers has a luminescence wavelength λ of, for example, 'C1.30 (μm) for the guide layer 13 and 1.5 (μm) for the active layer 14.
3 (μm), 1.30 for near tact layer 16
For example, the thickness of the guide layer 13 is 20 (nm), and the thickness of the active layer 14 is 10 (nm).
0 (71111). In addition, the diffraction grating at the interface between the rlWInP confinement layer 12 and the n-type InGaAsP guide layer 13 has a relationship between its period A and the resonant wavelength λ as follows, where n is the effective refractive index and m is a positive integer. To establish. Helium-cadmium (He-C
d) Laser light (wavelength 44], 6 (7Lm)) 0)
A diffraction grating formed by the 2-beam beam method and having a period of A-480 (71+11) was provided using a resist mask, and the wavelength λ due to the transition between the quantum levels E1 and Bhh shown in FIG. -155 [μm] light is selected.

In addition, in FIG. 4, 1) and (b) are cross-sectional views showing an embodiment having a multiple quantum well layer. In the embodiment, three layers are provided, and ■ nG
The other portions in which the aAsP barrier layer 15 is inserted are the same as in the previous embodiment.

The InQaA SP active layer 14 of this embodiment has a lumi-sensing wavelength λ9 of, for example, 152 [μm] and a thickness of, for example, i o (7 trn), and the InGaAsp barrier layer 15 has a lumi-insensitive wavelength λi of 152 [μm]. The example is 1. dLl(μr
n] The thickness is, for example, 20 mm (71 m). In
The composition and thickness of the guide layer 13 (GaAS)' and the composition and thickness of the guide layer 13 and In
The diffraction grating formed at the interface with the p confinement layer 12 is the same as in the previous embodiment, and in this embodiment as well, light with a wavelength of λ-1.55 (μm) due to the transition between the quantum levels is selected. The semiconductor light emitting device formed in this way has an active J*l quantum well structure and the gain beam of the active layer is discrete, so that the semiconductor light emitting device formed in this way has no resistance to temperature changes.
is smaller than in the continuous conventional case, and the range of stability against temperature changes is wide. Further, there is a gain difference between the TE mode and the TIVI mode, and since the gain of the TE mode is large, stable TE momo oscillation occurs.

Furthermore, since the selectivity of a single wavelength is good, extremely coherent light can be obtained, making it ideal for a light source for heterodyne communication and a light source for forming a hologram. (g) According to the present invention, as described in detail, quantum By further selecting the wavelength of the radiant light, which has a discrete spectrum due to the well structure, and performing laser oscillation, a semiconductor light emitting device with extremely high stability of a single oscillation wavelength and coherence '/' has been realized, and the homodyne heterogain detection method has been realized. etc., making it possible to significantly improve the quality of optical communication, and also.

Great effects can be obtained, such as making it possible to form a gram-forming light source into a semicircular body.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing the state concealment of carriers in semiconductor light emitting devices, Figure 3 (, ] 1. (b) and Figure 4 (a).
). (bl is a sectional view showing an embodiment of the present invention. In the figure, 11 is an n-type InP substrate, 12 is an n-type InP substrate, and 12 is an n-type InP substrate.
Confinement layer, 13 is n-type InGaASP guide layer, 14
11 is a GaASP active layer, 15 is a 1nGaASP barrier layer, and 16 is a p-type I+IP confinement layer. 17 is a p-type InP layer, 18 is an n-type ZnP layer, 19 is a pq
The lnGaAsP layers 20 and 21 represent electrodes. Akira 3 Fig. (a) (b) Fig. 4 - Fig. (a) (su)

Claims (1)

[Claims] 7. A semiconductor layer with a thickness less than the Doe-Ploey wavelength of an electron wave is used as an active layer.7. A semiconductor light emitting device comprising a periodic structure near the active layer that selectively returns light generated within the active layer.