JPH04316387A - Surface light emitting laser - Google Patents

Abstract

PURPOSE:To realize a surface light emitting laser having a low threshold value and a high efficiency. CONSTITUTION:A surface light emitting laser in which a first light reflecting layer 2, a cavity layer 3 containing an active layer therein, a second reflecting layer 5 are sequentially laminated on a main surface of a semiconductor substrate 1 to constitute an optical resonator by the first and second layers, wherein the active layer is formed of one quantum fine wire or quantum box 4 in which one side is formed in length for forming a quantum level.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a first light reflecting layer on the main surface of a semiconductor substrate, a cavity layer containing an active layer therein,
For a surface-emitting laser configured with a second reflective layer, the active layer in the cavity layer has one quantum wire or quantum box with one side having a length that forms a quantum level, The present invention relates to a surface emitting laser with an extremely low threshold and high efficiency compared to those of the prior art.

0002

[Prior Art] Generally, III-
In a group V compound semiconductor laser, an optical resonator is formed in a direction parallel to a substrate, and laser light is extracted from an end face (usually a cleavage plane) of the optical resonator. In this case, it is extremely difficult to two-dimensionally integrate lasers at high density on the wafer surface due to structural problems. In other words, each laser has a long optical cavity of 100 to 300 μm in length, so there is a limit to the number of lasers that can be integrated per unit area within a wafer, and the laser light is emitted parallel to the substrate. Therefore, in order to extract light in a direction perpendicular to the substrate, a 45° reflection mirror must be constructed separately from the laser portion. On the other hand, so-called surface-emitting lasers, which emit laser light perpendicular to the growth substrate, can be easily two-dimensionally integrated at high density due to their structure. Moreover, since the volume of the surface emitting laser is smaller than that of a normal laser, it is possible to realize a laser having a low threshold value of less than 1 mA. Limiting the scope to the surface emitting laser, the smaller the diameter of the surface emitting laser, the higher the injection current density inside the active layer, and a laser with a lower threshold value can be expected.

[0003] Due to rapid advances in growth and processing technologies, interest has been focused not only on the control in the film thickness direction but also in other two-axis directions, and attempts to realize quantum wires and quantum boxes continue. ing. That is, by replacing a conventional quantum well with a quantum wire or a quantum box, the degree of freedom of electrons is reduced, and the density of states of electrons is sharpened. In a laser, by using the quantum wire or quantum box, the gain spectrum becomes extremely narrow, and the contribution of the injected carriers to the gain at the laser oscillation wavelength becomes extremely large, and as a result, the current required for laser oscillation becomes It has been calculated that the threshold is significantly reduced. In addition, in the quantum wire and quantum box, even if the Fermi-Dirac distribution expands as the temperature rises, the density of states is extremely narrow as described above, so there is no density of states,
Changes in carrier distribution due to temperature changes are extremely small. Since the temperature change rate of the threshold current is caused by the temperature change of the carrier distribution, the temperature dependence of the threshold value is significantly improved. Improvements in modulation frequency or quantum noise characteristics are also expected.

However, in the case of ordinary lasers, when actually producing quantum wires and quantum boxes in the active layer,
A large number of elements must be manufactured in the direction of the resonator (usually several 100 μm), but in this case the variation in elements must be suppressed to at least 10% or less. For this reason, to date, it has not been possible to produce a laser that exhibits the effects of quantum wires or quantum boxes.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface emitting laser with a low threshold value and high efficiency.

[0006]

[Means for Solving the Problems] The present invention includes stacking a first light-reflecting layer, a cavity layer containing an active layer inside, and a second light-reflecting layer in this order on the main surface of a semiconductor substrate. In the surface emitting laser in which the first and second light reflecting layers constitute an optical resonator and the light emitted from the active layer is oscillated, one side of the active layer forms a quantum level. It consists of a single quantum wire or a quantum box.

[0007]

[Example] Below, the cavity layer is made of AlGaAs,
A case of a surface emitting laser using a GaAs quantum box with a side of 10 nm as an active layer at the center of the AlGaAs will be described. Note that the embodiments are merely illustrative, and it goes without saying that various changes and improvements can be made without departing from the spirit of the invention.

FIG. 1 is a structural diagram of one embodiment of the present invention. First, a MOCVD crystal growth method is used on an n-type GaAs substrate 1 to form a first light reflecting layer, each layer having an optical thickness of λ/4n (n is the refractive index) of the oscillation wavelength.
Five pairs of n-AlAs/GaAs reflective layers 2 were formed. Next, in order to form a cavity layer, first the optical film is made of undoped Al0.3Ga0 consisting of λ/2n of the oscillation wavelength.
．． A 7As layer and a 10 nm undoped GaAs layer are formed. Next, a square pattern with a side of 10 nm was exposed using EB exposure, and then the GaAs layer other than the square pattern was etched by ECR dry etching using chlorine, and then light etching was performed by chemical etching using sulfuric acid. , a quantum box 4 made of GaAs is formed. Subsequently, the GaAs square pattern was filled with an undoped Al0.3Ga0.7As layer using the MOCVD method, and the total optical film thickness was λ/n of the oscillation wavelength.
An undoped Al0.3Ga0.7As layer 3 is formed. Subsequently, the undoped Al0.3Ga0.7
On the As layer 3, 20.5 pairs of p-AlAs/GaAs reflective layers 5 are formed as a second light reflective layer, each layer having an optical thickness of λ/4n (n is the refractive index) of the oscillation wavelength. Finally, a square mask with sides of 2 μm is formed by resist patterning so that the GaAs active layer is centered. Then, the outside of the mask was etched down to the GaAs substrate using ECR etching using chlorine, and after planarization with polyimide, AnZnNi/A was etched on the top of the element.
p electrode 6 of u, AnZnNi/Au at the bottom of the element
The n-electrode 7 is formed and completed.

When current was injected into the surface emitting laser constructed as described above and the I-L characteristics were investigated, the I-L characteristics were found to be low at 0.5 mA, which is a much lower threshold than conventional ones.
It was confirmed that the curve rose and laser oscillation occurred. Furthermore, the oscillation spectrum has a wavelength determined by the etalon composed of the semiconductor reflective layer, and the half-width is also 1n.
m or less, which is below the resolution limit of a spectrometer, and is comparable to a normal surface-emitting laser.

The above is a case where a quantum box is used in the active layer, but similar results were obtained when a quantum wire was used in the active layer.

In the above embodiments, A is used as the cavity.
The explanation has been given using a surface emitting laser using a GaAs quantum box with a width of 10 nm as an active layer in the center of AlGaAs, but similar effects can be obtained with surface emitting lasers having other oscillation wavelengths. . For example, it can be easily inferred that the above effect can be obtained even in the case of a surface emitting laser using an InGaAsP quantum box or quantum wire as an active layer on an InP substrate.

0012

As explained above, in the surface emitting laser of the present invention, the first light reflecting layer is formed on the main surface of the semiconductor substrate, and the cavity layer is formed on the first light reflecting layer. By forming a cavity layer containing one quantum wire or quantum box at the center of the optical fiber, and then forming a second light-reflecting layer on the cavity layer, the light emission rate is extremely low compared to that of the conventional technology. We have achieved a highly efficient surface-emitting laser at the threshold value. Therefore, it has great economic effects, such as being able to be used as a light source for optical exchange, optical neural networks, and optical information processing.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of an embodiment of the present invention.

[Explanation of symbols]

1 n-type GaAs substrate 2 29.5 pairs of n-AlAs/GaAs reflective layers 3
Undoped Al0.3Ga0.7As layer 4 Quantum box 5 made of undoped GaAs 20.5 pairs of p-
AlAs/GaAs reflective layer 6 AuZnNi/Au
P electrode 7 AuGeNi/Au N electrode 8 Polyimide

Claims (2)

[Claims] 1. By stacking a first light-reflecting layer, a cavity layer containing an active layer inside, and a second light-reflecting layer in this order on the main surface of a semiconductor substrate, the first and second light-reflecting layers are stacked in this order. A surface emitting laser in which an optical resonator is configured with a light reflecting layer and oscillates light emitted from the active layer, the active layer having one side having a length to form a quantum level. A surface emitting laser characterized in that it is composed of a quantum wire or a quantum box. 2. The surface emitting laser according to claim 1, wherein the cavity layer has a thickness corresponding to a laser oscillation wavelength or a half thereof, and the active layer is formed in the middle of the cavity layer. A surface emitting laser characterized by: