JP2738040B2 - Semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to forming a confinement layer for current and generated light in a semiconductor light emitting device. Here, the term “semiconductor light emitting device” means an edge emitting type buried type semiconductor laser or light emitting diode. Substrate is p
The present invention can be applied to both n-type and n-type,
For simplicity, the p-type will be mainly described.

[Prior art]

In a semiconductor light emitting device, it is important to generate light efficiently. The injected current is converted to light by focusing on the light emitting area,
In addition, a semiconductor light emitting device having a buried type structure is widely used to confine generated light by utilizing a difference in refractive index. In this method, a light emitting region is formed at the center on a substrate, and confinement layers are formed on both sides thereof. The confinement layer plays a very important role to effectively confine the injected current in the light emitting region. The confinement layer is a factor that largely controls the performance of the semiconductor light emitting device. Heretofore, current constriction has been performed using the difference in conductivity type. The confinement layer is configured so that the pn junction is reverse-biased so that current flows only from the p-type substrate to the central light emitting region. Because of the reverse bias, no current flows in the confinement layer. However, a device utilizing a difference in conductivity type generates a leakage current in a high injection region in principle. This is because current may pass through the reverse bias of the pn junction. If there is a leakage current, the light output deteriorates. Therefore, in the case of a semiconductor laser using an n-type InP substrate, Fe
A structure using a confinement layer to which is added is proposed. When Fe is added to the confinement layer, Fe becomes an acceptor having a deep level and captures electrons, so that the resistance becomes high. For example, the specific resistance becomes 10 ⁷ Ωcm. The buried semiconductor light emitting device having such a confinement layer can be a semiconductor light emitting device having a small leakage current in principle. However, when the confinement layer is formed adjacent to the p-type semiconductor by this method, the n-cladding layer—the high-resistance layer—
It has a p-layer PIN structure. Holes are injected into the high-resistance confinement layer from the p-layer. Even with high resistance, the layer to which Fe is added is an electron trapping type semi-insulating layer. The trap level of Fe cannot capture the injected holes, and the holes flow into the confinement layer. With this, electrons flow. So-called double injection occurs. This causes current leakage through the confinement layer. In the case of the P-type substrate, it was found that the current confinement could not be sufficiently performed in the confinement layer to which Fe was added. Therefore, in addition to this, an improvement proposal was made. That is, Ti for capturing holes, which is a p-type impurity, is added to the confinement layer together with Fe. Inst.Phys.Conf.Ser.No.91: Chapter 3 Gallium Arsen
ide and Related compound, Heraklion, Greece, 1987 A.
G. Demtai, CH Joyner & TWWeidman “Ti-Fe Co-dop
ed semi-insulating InP grown by MOVPE "283 (1987) Electrons are captured by Fe and holes are captured by Ti. Positive and negative carriers contributing to the current are captured in this way, and the high resistance of the confinement layer (ρ to 10 ⁷ Ω · cm) for both electrons and holes, thus confining current and generated light in a narrow emission region.

[Problems to be solved by the invention]

In the method proposed above, the confinement layer contains Fe and
Both elements of Ti are added together. For this reason, it is extremely difficult to uniformly control the addition amount of each element in the crystal of the confinement layer. When actually tried, a high-resistance crystal could not be grown with good reproducibility. For example, one element may be segregated in the crystal, and the crystallinity may be deteriorated. Thus, there is a disadvantage that current leaks through the segregation part. A buried semiconductor light-emitting device having a light-emitting region and a confinement layer provided on a p-type or n-type substrate of a group III-V compound semiconductor, wherein the semiconductor has a confinement layer for preventing leakage current even when a large amount of current is injected. It is an object of the present invention to provide a light emitting device.

[Means for Solving the Problems]

In the semiconductor light emitting device of the present invention, in the case of a p-type substrate, the p-type semiconductor substrate has a light-emitting region made of a group III-V compound semiconductor at the center, and a current and generated light confinement layer on the side and upper and lower layers. The light emitting region and the first current and generated light confinement layer provided adjacent to the light emitting region and the p-type semiconductor substrate are made of a material having a high resistance by adding Ti, and an n-type semiconductor. The second current and generated light confinement layer formed on the first confinement layer adjacent to the layer is made of a material having high resistance by adding Fe. In the case of an n-type substrate, a semiconductor light-emitting device in which an n-type semiconductor substrate, a light-emitting region made of a group III-V compound semiconductor is formed in the center, and a current and generated light confinement layer is formed on upper and lower two sides. The first current and generated light confinement layer provided adjacent to the light emitting region and the n-type semiconductor substrate is made of a material having high resistance by adding Fe, and the first confinement layer adjacent to the p-type semiconductor layer. The second current and generated light confinement layer formed on the layer is made of a material having high resistance by adding Ti. This will be described with reference to the drawings. FIG. 1 is a sectional view showing a configuration example of a semiconductor light emitting device of the present invention using p-type InP as a substrate. The present invention relates to any III-
The present invention can be applied to a semiconductor light emitting device using a group V semiconductor, but here, an InP substrate is used as an example. 1 is an n-InP cladding layer, 2 is an InGaAsP active layer, 3 is p
-InP cladding layer, 4 is p-type InP substrate, 5 is Ti added
InP layer 6 is an InP layer to which Fe is added. On the p-type substrate 4, a light emitting region is provided in the center, and a confinement layer is provided on the side. The light emitting region includes a p-InP cladding layer 3, an InGaAsP active layer 2, and an n-InP cladding layer 1. The current flows in the order of the p-InP cladding layer 3, the InGaAsP active layer 2, and the n-InP cladding layer 1. The confinement layer is composed of two upper and lower layers formed on both sides of the light emitting region. The first layer is Ti-dope InP5. Second
The layer is Fe-doped InP6. A first substrate adjacent to the P-type substrate 4 and the active layer 2 (light emitting region)
Is an InP layer 5 to which only Ti is added. That is, a portion in contact with the p-type layer is defined as a Ti-dope confinement layer. The second confinement layer in contact with the n-type cladding layer thereon is
The InP layer contains only Fe. That is, in the first confinement layer doped with Ti, holes can be captured, so that the first confinement layer is adjacent to the p-type region. Since the second confinement layer doped with Fe can capture electrons, it is provided adjacent to the n-type layer. The confinement layer consisting of two layers captures each of the majority carriers of the adjacent semiconductor layers even if they flow in, so that both layers become high-resistance crystals. The injection current can be narrowed by the action of the two confinement layers.

[Action]

In this invention, the confinement layer is divided into two layers, and the roles of the confinement layers are clearly defined. A Ti-dope confinement layer capable of capturing holes is made adjacent to the p-type semiconductor. An Fe-dope confinement layer capable of capturing electrons is adjacent to the n-type semiconductor. Adjacent to the p-type is the confinement layer to which Ti is added, so that the holes, which are majority carriers flowing from the p-type layer, are captured to reduce carriers contributing to current. The one adjacent to the n-type serves as a confinement layer to which Fe is added, which captures electrons, which are majority carriers flowing from the n-type layer, and reduces the number of carriers contributing to current. Thus, the confinement layer is divided into two layers, and the type of element added to each confinement layer is limited to one type. Since there is only one kind, a good single crystal can be grown while controlling the amount of addition freely and accurately with good reproducibility. High resistance without deteriorating crystallinity (ρ ≧ 16
⁶ Ω · cm) The confinement layer can be easily grown. By increasing the resistance of the confinement layer, a stable current confinement structure can be formed. Therefore, a semiconductor light emitting device with less current leakage can be manufactured even in a high current injection region.

【Example】

FIG. 1 is a sectional view of a semiconductor light emitting device according to one embodiment of the present invention. On a p-type InP semiconductor substrate 4, a p-type InP layer 3 and an InGaAsP
The active layer 2 and the n-type InP layer 1 are epitaxially grown to form a double hetero structure. This is shaped into a mesa shape leaving a light emitting portion by etching. The InP layers 5 and 6 as confinement layers to which Ti and Fe are added are separately and sequentially laminated on the etched portions. It is a kind of embedded double hetero racer. Ti is added to the first confinement layer 5 to about 1 × 10 ¹⁸ cm ⁻³ . The second confinement layer 6 contains Fe at ~ 1 × 10 ¹⁶ cm ^−3.
Add about. Each thickness is controlled in the range of 1 to 2 μm. The Ti-doped confinement layer 5 is always in contact with both sides of the active layer. Most of the both sides of the n-type InP layer 1 are in contact with the Fe-doped confinement 6. As described above, since the current and generated light confinement layers are formed in two layers, current leakage due to double injection does not occur in principle. There is no leakage even in a high current injection region, and light is emitted efficiently. In addition, since the addition amounts of Fe and Ti are controlled to be the minimum within a range where holes and electrons can be compensated, the confinement layer has good crystallinity and a withstand voltage of about 10 V. Seen in the case of the conventional technology where Fe and Ti are added at once,
Leakage and in-plane variation due to deterioration of crystallinity are reduced. This is because the confinement layer has two layers, and the amounts of Fe and Ti added are individually controlled. Since the uniformity of the in-plane distribution of Fe and Ti in the confinement layer is improved, in this structure, the reproducibility of the formation of the confinement layer is improved, and the yield is improved. The confinement layer according to the present invention is also applicable to a semiconductor laser having the structure shown in FIG. On a p-type InP substrate 10, a Ti-doped InP layer 5, a Fe-doped InP
The P layer 6 is epitaxially grown as a confinement layer.
A central light emitting portion is etched in a wedge shape, and p
After forming the n-type InP layer 9 and the InGaAsP active layer 8, the n-type
The InP layer 7 is epitaxially grown. This can geometrically narrow the current narrower. Also in this example, the Ti-doped confinement layer 5 is a p-type InP
It is in contact with layer 9 and active layer 8. The Fe-doped confinement layer 6 is in contact with the n-type InP layer.

【The invention's effect】

As described above, in the present invention, a confinement layer is formed by adjoining crystals containing Fe and Ti as additives so as to make use of their respective characteristics in n-type and p-type. Thereby, a semiconductor laser with good reproducibility and high luminous efficiency can be obtained. There is no variation in the confinement layer between the added amounts of Fe and Ti, which was one of the conventional problems. By properly combining a p-type or n-type conductivity type with an additive to a crystal in contact with the conductivity type, it can be used for a current confinement layer of a semiconductor laser. In addition, it can be used for various purposes such as an element isolation insulating layer of an optoelectronic integrated circuit.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor light emitting device according to one embodiment of the present invention. FIG. 2 is a sectional view of a semiconductor light emitting device according to another embodiment of the present invention. FIG. 3 is a cross-sectional view of a conventional semiconductor laser structure having a confinement layer to which Fe and Ti are simultaneously added. DESCRIPTION OF SYMBOLS 1 ... n-type InP layer 2 ... InGaAsP active layer 3 ... p-type InP layer 4 ... p-type InP substrate 5 ... Ti-doped InP layer 6 ... Fe-doped InP layer 7 ... n-type InP layer 8 ... ... InGaAsP active layer 9 ... p-type InP layer 10 ... p-type InP layer 11 ... Ti, Fe doped InP layer

Claims (2)

(57) [Claims] 1. A semiconductor light emitting device comprising a p-type semiconductor substrate and a light emitting region made of a group III-V compound semiconductor formed at the center and two upper and lower confining layers for current and generated light formed side by side. The first current and generated light confinement layer provided adjacent to the region and the p-type semiconductor substrate is made of a material having high resistance by adding Ti, and is formed on the first confinement layer adjacent to the n-type semiconductor layer. A semiconductor light emitting device characterized in that the second current and generated light confinement layer formed in the semiconductor light emitting device is formed by adding Fe to increase the resistance. 2. A semiconductor light-emitting device comprising: an n-type semiconductor substrate; a light-emitting region made of a group III-V compound semiconductor formed at the center; The first current and generated light confinement layer provided adjacent to the region and the n-type semiconductor substrate is made of a material having high resistance by adding Fe, and is formed on the first confinement layer adjacent to the p-type semiconductor layer. The light emitting device according to claim 1, wherein the second current confinement layer formed therein has a high resistance by adding Ti.