JPH03214618A - Structure of quantum wire and formation method of quantum wire - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser whose oscillation threshold current is small by a method wherein a groove whose width and depth are the mean free path or lower of the electron is formed, an insulator layer of several tens of angstroms is laminated on parts other than side faces of the groove and, after that, is grown selectively and the groove is filled. CONSTITUTION:An insulator layer 12 of several tens of angstroms is formed on parts other than side faces of a groove; a second semiconductor 13 whose forbidden-band energy is smaller than that of a semiconductor 11 constituting the side faces of the groove is filled into the groove. In addition, a third semiconductor 14 whose forbidden- band energy is larger than that of the second semiconductor 13 and whose conductivity type is different from a first conductivity type is laminated on the groove. Consequently, when an electric current flows between the first semiconductor 11 and the third semiconductor 14, electrons and holes flow effectively into the quantum wire layer 13, and the current injection efficiency is increased remarkably. In addition, the size of the quantum wire layer 13 is controlled when it is filled. As a result, it is possible to restrain an irregularity in a quantum confinement effect by the fluctuation of a shape. Thereby, it is possible to obtain a semiconductor laser whose oscillation threshold current is small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a quantum wire structure and a quantum wire forming method.

[Conventional technology]

Conventionally, as a structure for injecting electrons and holes into a microstructure,
Japanese Journal of Japanese Journal of the Japanese Journal
Applied Physics Volume 26 L225 Page 1
987).

In this structure, electrons and holes have a potential energy of 7
Only the difference is implanted into the microstructured part.

In addition, as one of the conventional methods for forming quantum wires, a method has been attempted in which a quantum wire is formed by re-growing an arch-shaped structure of several hundred angstroms (Japanese Journal of Applied Physics, Vol. 28, L108).
3 pages 1989). In this formation method, Ga
After growing an MQW consisting of GaAs and AIAs on an As (001) substrate, <1. 1. 0) Cleave along the plane and apply thermal etching in an ultra-high vacuum.
a After forming a 900 angstrom trench structure on the AS layer, p-GaAs is regrown and buried. G a A. forming MQW. The s-layer has n-type conductivity and electrically isolates the regrown p-GaAs.

This method for forming a quantum wire has the feature that the width of the wire can be accurately controlled by the layer thickness of the MQW, and it is possible to form a quantum wire having a good quantum confinement effect.

[Invention or problem to be solved]

However, in conventional quantum wire structures, current injection efficiency is low because current cannot be forcibly injected into the quantum wire portion.
Characteristics that utilize the quantum confinement effect, such as low threshold oscillation characteristics, cannot be expected in semiconductor lasers.

In addition, in the conventional quantum wire formation method, the regrowth direction is < 1 1
．． 0 > direction, and troplets of group (I) atoms are likely to be formed in the regrown layer, making it difficult to achieve good epitaxial buried growth.

[Means to solve the problem]

In the quantum wire structure according to the invention, in a first semiconductor having a first conductivity type having a groove having a width and depth equal to or less than the mean free path of an electron, a portion of the quantum wire structure having a width of several tens of angstroms is formed in a portion other than the side surface of the groove. The groove has an insulating layer and is embedded with a second semiconductor having a forbidden band energy smaller than the forbidden band energy of the semiconductor forming the side surface of the groove, and a second semiconductor is further placed on the buried groove. It is characterized in that a third semiconductor having a forbidden band energy larger than the forbidden band energy of , and having a conductivity different from that of the first conductivity type is laminated.

Further, the quantum wire forming method according to the present invention includes a step of forming a ridge with a width and depth equal to or less than the mean free path of an electron, and a step of laminating an insulating layer of about several tens of angstroms on a portion other than the side surface of the groove. The method is characterized in that it includes at least a step and a subsequent step of burying the trench by selective growth.

[Effect]

Hereinafter, the operation of the present invention will be explained using the drawings.

FIG. 1 is a schematic diagram of a quantum wire structure according to the first invention. In the m structure, an insulator 12 is thinly formed on a first semiconductor 11 having a groove other than the side surfaces of the groove, and a second semiconductor (quantum wire layer) 13 filling the groove is formed on the insulator 12. Further, a third semiconductor 14 having a different conductivity type from the semiconductor 11 with a larger forbidden band energy than the quantum wire layer [3] is laminated thereon. In this structure, when a current is passed between the first semiconductor 1 and the third semiconductor 4, electrons and holes avoid the insulator 12 and effectively flow into the quantum ffA line layer 13 with the smallest forbidden band width. current injection efficiency is significantly increased. Furthermore, in this horizontal structure, the quantum wire layer 1
Since the size of the radius is accurately controlled by embedding, variations in the quantum confinement effect due to shape fluctuations can be suppressed.

5. FIG. 2 is a schematic diagram showing the third step of the quantum wire forming method according to the present invention, that is, the step of burying and growing the second semiconductor in the trench. In the method for forming a quantum wire according to the present invention, a thin insulator 21 is formed in a portion other than the side surfaces of a trench having a width and depth equal to or less than the mean free path of an electron, and is selectively grown only on the semiconductor surface of the trench side surface. Fill in the groove. During this embedding step, the atoms physically adsorbed onto the insulator 21 either redistribute or are diffused and taken in to the semiconductor portion on the side surface of the groove, and selectively laterally develops epitaxial growth. Therefore, only the groove portion can be completely filled. Manako's quantum wire forming method is based on the semiconductor surface 23 at the bottom of the trench.
This method is particularly effective when direct epitaxial growth on the groove side surface 22 is difficult and growth on the groove side surface 22 is easy.

[Example] FIG. 3 is a diagram illustrating an example of a quantum wire structure according to the present invention. On the n-type (001) plane orientation GaAs substrate 31, an n-type (Si-doped 75 x 1.017 cm-') Ga
A multiple quantum well layer (100 people/100 people x
30 periods) are formed, and < 1 perpendicular to the multi-quantum well layer.
1. A groove structure is formed in the O > direction. The groove bottom is made of a GaAs layer, and the side surfaces are made of AI. ), 5 Ga0
It is composed of 5As layers and has a depth of about 150 people. A Si02 film 34 is laminated on a portion other than the side surfaces of this groove structure. Further, a GaAs quantum wire layer 35 is selectively buried in the groove portion, and a p-type (Be-doped 5×10
17cm-3) A 1 03G aQ, 7 A s
N3 6 is 5000 people and p type (Be doped 5
1018cm-3) Ga As cap layer 3
7 is stacked with 3000 people.

38 The three electrodes are a p-type electrode and an n-type electrode made of Ti, Au, Au-Ge, etc., for example.

Therefore, when a forward voltage is applied to the quantum wire structure described above, the holes and electrons injected from the p-type electrode 38 and the n-type electrode 39, respectively, avoid the Si02M 34 and flow into the GaAs quantum wire layer 35, which has a low potential energy. . In the GaAs quantum wire layer 35, both holes and electrons are confined two-dimensionally and are in a quasi-one-dimensional state, so the density of each state is concentrated in a narrow energy key region, and the recombination spectrum is extremely narrow. Therefore, all the carriers effectively contribute to laser oscillation, and a semiconductor laser with a very small oscillation threshold current can be obtained.

FIGS. 4(a), (b), and (c) are explanatory diagrams of an embodiment of the quantum wire forming method according to the present invention.

a) Groove tfi3jt is ( 0 0 ]. ) plane GaA
G a A S and A I 03G aQ on the s substrate 4]
．． Multiple quantum well structure consisting of 7 A s (1-00 people/1
00 people x 30 cycles) and grow this (0 0
]. ) surface, and the GAas layer was thermally etched in a high vacuum to form the groove structure 42. The depth of the trench is approximately 120 people.

b) Approximately 20 Si02 films 43 are added to the above-mentioned wave structure (1
1. Lamination was performed from the 0> direction. At this time, place S on the side of the groove.
Lamination was performed using a growth method with good directionality to prevent iOzJI from being stacked. Here, an electron gun type evaporator was used for Si, and an 02 molecular beam containing 03 was used for oxygen.

c) G a As quantum wire layer 44 is selectively grown by MBE at a substrate temperature of 720°C. At this substrate temperature, GaAs was not deposited on the Si02 film 43 and grew in the <001> direction from the side surfaces of the trench, achieving good buried growth. Particularly in the case of this example, direct epitaxial growth on the groove bottom surface 45 tends to form Ga droplets and it is difficult to obtain good crystallinity, but by using this formation method, good buried growth is possible. It became.

After this, A I0.3 Ga (,,7 A
A quantum wire structure is completed by forming an s layer (not shown).

Although this embodiment has been described using GaAs as an example, the material is not limited thereto. For example, InGa on InP
It may be AsP-based, and the insulator may also be SiN. Is the formation method of the Wei ellipse also FIB'? It may also be one using EB etching. The substrate surface orientation is also not limited. Also, any growth method that allows for selective growth is fine.

〔Effect of the invention〕

According to the present invention, a semiconductor laser with high current injection efficiency and a very small oscillation threshold current can be obtained.

Further, according to the manufacturing method of the present invention, a quantum wire with small quantum wire width fluctuation can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a quantum wire structure according to the present invention. FIG. 2 is a schematic diagram of the quantum wire forming method according to the present invention. FIG. 3 is a diagram for explaining an embodiment of a quantum wire structure according to the present invention, and FIG. 4 is a diagram for explaining an embodiment of a quantum wire forming method according to the present invention. In the figure, 11: first semiconductor, 12: insulator, 3: second semiconductor (quantum wire layer), 14: third semiconductor,
2]... Insulator, 22... Groove side surface, 23... Bottom semiconductor surface, 3 1 - RL type GaAs substrate, 3 2
- n-type GaAs layer, 3 3 /n-type AI 6.
5 Gao, 5 A s10 layer, 34-Sin2 film, 3 5-Ga As quantum wire layer, 36 ・p-type A 1 0.3 Ga. 0.7
AS layer, 3 7 ---GaAs cap layer, 38
...p-type electrode, 39...n-type electrode, 41...Ga
As substrate, 42...groove structure, 43---Si02 film,
4 4 - G a As quantum wire layer, 45 . . . groove bottoms are shown, respectively.

Claims (1)

[Claims] 1. A first semiconductor having a first conductivity type having a groove with a width and depth equal to or less than the mean free path of an electron, and an insulation of approximately several tens of angstroms in a portion other than the side surfaces of the groove. It has a body layer,
The trench is filled with a second semiconductor having a forbidden band energy smaller than the forbidden band energy of the semiconductor forming the side surface of the trench, and a second semiconductor having a forbidden band energy larger than the forbidden band energy of the second semiconductor is placed above the buried trench. A quantum wire structure characterized in that a third semiconductor having a band energy and a conductivity different from the first conductivity type is laminated. 2. A process of forming a groove with a width and depth equal to or less than the mean free path of an electron, a process of laminating an insulating layer of several tens of angstroms on the part other than the side surfaces of the groove, and burying the groove by selective growth. A method for forming a quantum wire, comprising at least the steps of: