JPS6072283A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To contrive to improve the temperature characteristic by a method wherein the values of the energy band gaps of an active layer and a clad layer and those of the gradients thereof are suitably selected. CONSTITUTION:The titled device is formed by lamination of an n<+> type Ga buffer layer 2, an n type AlxGa1-xAs clad layer 3, an n type AlyGa1-yAs grated clad layer 4, a GaAs clad layer 5, a p<+> type AlzGa1-zAs clad layer 6, and a p<+> type GaAs contact layer 7 on an n<+> type GaAs semiconductor substrate 1. In this constitution, the layer 3 can have a value of 0<x<=1, and the layer 4 0<y<=1, and the layer 5 can be set any type of n, p, i, and un-dope. The layer 6 has a value of 0<z<=1, where the range of (z) is the same as that of the (y) value of the layer 4, particularly larger than 0.2. It is preferable that the variation in the composition ratio of the layer 4 is parabolic, but it can be also linear. This manner enables the reduction in the amount of leakage of carriers having the small effective mass to the clad layer even in the increase in temperature, resulting in the improvement of the temperature characteristic with the property of low threshold value being maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to quantum well lasers or multi-quantum well lasers.
This invention relates to improvements in semiconductor light emitting devices called ell:MQW) lasers.

Conventional technology and problems Conventionally, double hetero lasers (
DH laser) is known.

FIG. 1 represents the energy band diagram of a simple GaAs-based DH laser.

In this DH laser, the GaAs active layer is made of n-type AβGaA
It has a structure sandwiched between an s-cladding layer, a p-type AiV, and a GaAs cladding layer, and the GaAs active layer has a narrow band gap and a high refractive index compared to each cladding layer. It is designed to confine carriers and light.

As mentioned above, the H laser is used for liquid phase epitaxial growth (l
It has been created by applying the iquid phase epitaxy (LPE) method.

However, in recent years, MBE (molecular beam
epitaxy) method or MOCVD (metal
organic chemical vapor
deposition) method, or VPE (vap
Our pklase ep1taxy) method, etc.
A technique for growing thin crystalline films with good reproducibility has been established, and the GaAs active layer in the DH laser has been grown thinly using this technique. A semiconductor light emitting device is called a quantum well laser.

In this quantum well laser, electrons confined within an extremely thin active layer by a potential barrier begin to exhibit properties as quantum mechanical waves, creating discrete energy levels, and transitions between these discrete levels. I am trying to use it.

Although the quantum well laser has excellent performance in reducing the dark value, its structure simultaneously confines carriers and light, so it is important to optimize both confinement effects. is difficult, especially when it comes to light confinement.

Therefore, a semiconductor light emitting device having the characteristics shown in the energy hand diaphragm shown in FIG.
RIN-3CH (graded index wave (
<uide 5eparate confinemen
A hetero'5structure laser was developed.

As can be seen from the figure, the G RI N S CH laser has n
By continuously changing the composition of the 9AAGaAs cladding layer and the p-type AAGaΔS cladding layer, a refractive index gradient is generated, and the confinement of carriers and light can be controlled separately, resulting in further improvement. This aims to achieve a low threshold value.

This GRIN-3CH laser has the lowest CW (continuous CW) among the currently reported lasers.
wave) has a threshold value.

However, although this low threshold value is not a problem at high temperatures, as the temperature rises, it becomes impossible to maintain this characteristic.

Immediately, as the temperature rises, Ga A s /l!
Among the carriers, which are electrons or holes, to be confined in the j-type layer, carriers with a small wJwm are particularly likely to jump out of the well (so that the electrons are likely to jump out of the well) into the p-type AffGaAs cladding layer, which has a composition gradient. The amount of light that leaks increases.Therefore, recombination occurs and light is emitted, but it goes without saying that such light is essentially invalid light.

OBJECTS OF THE INVENTION The purpose of the present invention is to slightly modify the GRIN-3CH laser to obtain a semiconductor light emitting device with greatly improved m-power characteristics.

Structure of the Invention The present invention provides an active layer having a thickness capable of generating quantum wells;
a cladding layer having the same conductivity type as carriers having a smaller effective mass among the carriers in the active layer and having an energy band gap gradient decreasing toward the active layer side;
The carrier IJ4 in the active layer is provided with a cladding layer having a conductivity type opposite to that of the carrier with a small effective mass and larger than the energy hand gap on the active layer side in the cladding layer. With this configuration, the amount of carriers having a small effective mass in the active layer leaking into the cladding layer having a conductivity type opposite to the active layer is reduced, and the rate of generation of ineffective light is reduced. In addition, when comparing electrons and holes as carriers in the active layer,
Since the effective mass of a hole is about 10 times that of an electron,
Even if the temperature rises, there is no need to worry about holes leaking into the cladding layer.

Examples of the invention FIG. 3 is a cutaway front view of essential parts of an embodiment of the present invention.

In the figure, ■ is an n+ type GaAs semiconductor substrate, 2 is an n+
type GaAS buffer layer, 3-ban type Al1xG a I-
x As cladding layer, 4ban type A, ffyGal-y
As graded cladding layer, 5 is GaAs active layer,
6 is p-type A7! A zGa14As cladding layer and a 7bp+ type GaAs contact layer are shown, respectively.

In the above example, the main characteristics of each layer are listed as follows: n-type A7! Regarding xGal-xAs crat layer 3, Q<
x≦1 For example, X20.5 Impurity concentration C'= I X 10' ~3 X 10+
8 (cm-3) Thickness d 1.5 [μm] N-type A7! For yGal-yAs graded cladding layer 4, Q<y≦1, e.g. yα0.5 to 0.2, impurity concentration C=1 x 10I7 to 3 x 10”
(cm') Thickness d 0.2 [μm] For GaAs active N5, any of n+1)+1+undoped is possible Thickness d=>75
(people) The thickness is not around 0.15 (μrn), which is normally adopted in this type of DI-1 structure, but around several tens to hundreds of people, where the quantum size effect appears. Thickness can be adopted.

p-type A (l z Ga +-2A s cladding layer 6
For 0<z≦1 For example, 2 and 0.4 The range of 2 is n-type A 7! yGa is the same as the y value of the yAs graded cladding layer 4, especially a value larger than ~0°2.

Impurity concentration C= l X IO17~10'' (c
m-3) Thickness d 1.5 [μm] Impurity concentration C≧ for p+ type GaAs contact layer 7
10I9 (cm-3) Thickness d: 0.2 [μm] etc.

The compositional change of the n-type Aβy Ga 1-y As graded cladding layer 4 is preferably parabolic, but there is no practical problem even if it is linear. Also, G
aAs activity N5 is lower than each cladding ff13, 4°6, etc. A7! It may contain.

FIG. 4 is an energy hand diagram of the embodiment described with respect to FIG.

According to the figure, it will be understood that there is an effect of preventing leakage of electrons.

FIG. 5 shows an energy band diagram in an embodiment in which the present invention is applied to a GRTN-3CH laser having a multiple quantum well structure.

It is clear that according to this embodiment, the excellent confinement effect in a normal multiple quantum well laser is added to the effect of the embodiment described with reference to FIGS. 3 and 4.

FIG. 6 shows an energy band diagram of an embodiment further modified from the embodiment of FIG.

In this example, the n-type A7! shown in FIG. yGa
1-y As graded clad N4, the energy band gear slope is made shallower, and Ga As
The magnitude of the energy band gap in the Illiii layer 5 is similar to that of the embodiment shown in FIG.

In this way, electrons injected from the n-type AβyGa to yAS graded cladding layer 4 become p-type A j2
It becomes easy to travel in the S cladding layer 6 direction to z G a 1-z.

By the way, each of the above-mentioned embodiments exhibits an excellent effect in confining carriers, but with respect to light leakage, although there is no practical problem, a slight deterioration in performance cannot be avoided.

In order to minimize this deterioration in performance, the following embodiment may be adopted.

FIG. 7 is a cutaway front view of essential parts showing this embodiment, and the same portions g1 as those explained with reference to FIG. 3 are indicated by the same symbols.

The difference between this embodiment and the embodiment shown in FIG. 3 is that p-type Al
2. The composition and thickness of the GaI-ZA S cladding layer 6 are selected to such a value that carriers with a small effective mass, that is, electrons in this case, do not penetrate through the tunneling effect, and the GaAs active layer 5 and the p-type A/2uGa+-uAs graded cladding layer 8 and the p-type Aj2νG a 1-V between the
A s cladding N9 is interposed therebetween.

In this example, the main characteristics of each layer are listed as follows: p-type A (12G a page - 2 As for the cladding layer 6, for example, Z = 0.4, thickness d, about 500 [people]) p-type A j! u G a4.uA s graded
Regarding the cladding surface 8, for example, U is 0.2 to 0.5 and impurity concentration C-1 x 1017 to 3 x 10'9 [cm-
3] Thickness dα0.2Cμm] About p-type Aβv Gal-yAs cladding layer 9 Q<v≦1 For example ■ 0.5 Impurity concentration C=I X 10I7~3 X 10''
(am-3) Thickness d 1.5 [μrn) etc.

FIG. 8 is an energy hand diagram of the embodiment described with respect to FIG.

According to the figure, for electrons, p-type A E z G a
1-2As clad N6 becomes an effective barrier, and
For light confinement, p-type Aβu G a+−uA
It will be appreciated that the graded cladding layer 8 works effectively.

FIG. 9 shows energy consumption in an embodiment in which the semiconductor light emitting device technology explained in FIGS. 7 and 8 is applied to a GRIN-3CH laser having a multiple quantum well structure.
Represents a hand diagram.

According to this embodiment, it is clear that the excellent confinement effect in a normal multiple well laser is added to the effect of the embodiment described with reference to FIGS. 7 and 8.

Note that ΔX shown in the figure may be O.

For each of the above examples, A (l Ga As / Ga
Although the As system has been described, the present invention is not limited thereto, and other systems such as 1nGaAsP/]nP system can also be used.

Effects of the Invention The semiconductor light emitting device of the present invention includes an active layer having a thickness capable of generating a quantum well, a carrier having a small effective mass among the gears in the active layer, and having the same conductivity type and facing toward the active layer side. a cladding layer having an energy hand gap gradient that decreases as the energy hand gap gradient decreases, the energy hand gap gradient on the active layer side in the cladding layer having a conductivity type opposite to that of the carriers having a small effective mass among the carriers in the active layer; - Since the structure includes a cladding layer having a gap larger than the gap, even if the temperature rises, it is possible to reduce the amount of carriers with small effective mass leaking into the cladding layer. Moreover, it does not cause appreciable fluctuations in the energy band gap gradient or the refractive index gradient that affects light confinement.

As described above, according to the present invention, since both carrier confinement and light confinement can be effectively performed, it is possible to improve the temperature characteristics while maintaining the low threshold property, and it is possible to improve the temperature characteristics while maintaining the low threshold property. Temperature To ~100 (K) (
From the value of Ith=Io exp(T/To), To≧1
Improved to 50(K).

[Brief explanation of drawings]

Figure 851 is an energy hand diagram of a normal DH laser, Figure 2 is an energy band diagram of a GRIN-3CH laser, Figure 3 is a cutaway front view of essential parts of an embodiment of the present invention, and Figure 4 is an energy hand diagram of a conventional DH laser. The figure shows an energy band diagram of the embodiment shown in FIG. 3, FIG. 5 shows an energy band diagram of another embodiment of the invention, and FIG. 6 shows a further embodiment of the invention. Example energy
7 is a cutaway front view of essential parts of still another embodiment of the present invention; FIG. 8 is an energy hand diagram of the embodiment shown in FIG. 7; FIG. It is an energy hand diagram of yet another embodiment in the invention. In the figure, 1 is an n+ type GaAs semiconductor substrate, 2 is an n+
type GaAs buffer layer, 3 is n-type A/2xGal-xA
s cladding layer, 4 is n-type A jl! y G a 1-
y A S graded cladding layer, 5 is G a A
S % outer layer, 6 is p-type A
s cladding layer, 74; l: I)" type GaAs contact layer. Patent applicant: Fujitsu Ltd. Representative Patent Attorney Akio Aitani Representative Patent Attorney Hiroshi Watanabe - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Procedural amendment November 19, 1980 Director General of the Patent Office Kazuo Wakasugi (Examiner of the Patent Office) 1 Indication of the case 1988 patent Application No. 178193 2 Name of the invention Semiconductor light emitting device 3 Relationship to the case of the person making the amendment Patent applicant address 1015 Kamiodanaka, Nakahara-ku, Yozaki City, Kanagawa Prefecture Name (522) Fujitsu Limited Representative Takuma Yamamoto 4 Agent Address 20-7-6 Toranomon-chome, Iso-ku, Tokyo Subject of amendment Column for brief description of drawings in Detailed Description of the Invention 19 of Mei 4111. Drawings. 7 Contents of amendment As attached (1) Description The description on page 12, lines 8 to 11 is changed to [
FIG. 10(A) is a main part cutaway front view showing still another embodiment of the present invention. In the figure, 11 is an n+ type GaAs semiconductor substrate, 12 is an n4 type GaAs buffer layer, and 13 is an n type A j2
G a I-X A s cladding layer, 14 is n-type AAy
G a I-y A s graded cladding layer, 1
5 is a GaAs active layer, 16 is a p-type Anz Ga, -, A
s graded cladding layer, 17 is I)! ! ! A
II uGaI-uAS cladding layer, 18 is p1 type G
An aAs contact layer is shown in each case. In the above embodiment, the main characteristics of each layer are listed as follows:
<x≦1 For example, X~0.5 Impurity concentration C=lXlOI7~5X10I8 (cm-'
) Thickness d~1.5 [μm] n-type Aj? , Gap-yAs graded cladding layer 14 Q<y≦1 For example, y~0.5 to 0.2 Impurity concentration C=I X 10'7 to 5 X 10'8
(cm-3) Thickness d~0.2 [μm] GaAs active layer 15 can have any thickness d~G (n+p+j+ undoped)
nm) The thickness is d ~ 0, which is normally adopted in this type of D11 structure.
．． It is possible to adopt not only a thickness in the vicinity of 15 C μm, but also a thickness of several nanometers to several tens of nanometers at which the quantum size effect appears. p-type Aj! 20a+-z For the As graded cladding layer 16, a value of 2 at the interface with the active layer 15 is n-type Aff. The value of y is made larger than the value of y in the Ga1-yAs graded cladding layer 14. Therefore, in this case, the value is set to be larger than 0.2. For example, z-0.3 to 0.5 impurity concentration C= L X I O" ~ 3 X I O1
2 (cm-") Thickness d ~ 0.2 [μm] P-type Al! u Ga +-u AS For the S cladding layer 17, for example, U ~ 0.5 Impurity concentration C = 1 x l O" ~ 3 101
9 (cm-3) thickness d~1.5 [μm] 1) Impurity concentration C≧1019 (Cm-3) for the + type GaAs contact layer 18, thickness d-0.2C μm], etc. The composition change of the n-type AβyGa+-yA'' graded cladding layer 14 or the p-type Aβ, Ga, -, , S graded cladding layer 16 is preferably parabolic, but may be linear. There is no problem in practical use.Also,
The GaAs active layer 15 includes each cladding layer 13, 14, 16
．． It may contain Aβ of a lower value than 17 or the like. FIG. 10(B) is an energy hand diagram of the embodiment described with respect to FIG. 10(A). According to the figure, it will be understood that there is an effect of preventing leakage of electrons. Figure 11 shows GRIN-S C with multiple quantum well structure.
FIG. 3 shows an energy hunt diagram in an embodiment in which the present invention is applied to an H laser. According to this embodiment, it is clear that the excellent confinement effect of a normal multiple quantum well laser is added to the effect of the embodiment described with reference to FIGS. 11(A) and 11(B). Note that the illustrated ΔX may be O. In each of the above embodiments, A j! G a As / G a
Although the As system has been described, it is not limited thereto, and for example, I n Ga As ])/ I n
Other materials such as P-based materials can also be used, and structurally, planar strip type, +311 (bu
ried heteros Lru (:
Lur e ) type, C3P (channel
e d su b st r a t e p
Ia n ar) type, BC3 (buried con
vexwaveguide 5structure) type,
VSIS (V-cl+anneled 5ubstr
The method can be applied to all types of semiconductor lasers in which the transverse mode is controlled, such as the 1nner 5tripe) type. ”, corrected. (2) The description on page 1, page 4, line 7 of the same page is changed to ``Nergy hand diagram.
FIG. 10(B) is an energy band diagram of the embodiment shown in FIG. 10(A), and FIG. 11 is an energy hand diagram of yet another embodiment of the present invention. ”, corrected. (3) Figures 10 (A) and (B) and Figure 11 will be supplemented. 8 Attached document catalog drawing (Figure 10 (A), (B), 11th cabinet) 1 copy

Claims (1)

[Claims] an active layer having a thickness capable of generating a quantum well; an active layer having the same conductivity type as carriers with a smaller effective mass among carriers in the active layer;
A cladding layer having a band gap gradient, which has a conductivity type opposite to carriers having a small effective mass among carriers in the active layer, and has an energy band gap larger than that of the active layer side in the cladding layer. A semiconductor light emitting device comprising a cladding layer having the same.