JPS63302585A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser which can effectively enclose a current in an active layer, generate a laser oscillation with a less current and efficiently convert the current into a light by disposing the inner end of a third region which forms a current narrowing layer under an active region. CONSTITUTION:A first conductivity type first region 3, an active region 2 of a predetermined width for forming a junction with the region 2, a second conductivity type second region 1 for forming a junction with the region 2, a second conductivity type third region 4 in contact with the end of the region 2, and a fourth region 5 for forming a p-n junction with the region 4 are provided. A current narrowing layer is formed of the regions 3, 4, 5, and the inner end of the region 4 for forming the current narrowing layer is disposed under the region 2. For example, the region 3 is of a P-type InP clad layer, the region 2 is of an InGaAsP active layer 2, the region 1 is of an n-type InP clad layer, the region 4 is of an n-type InP current narrowing layer 4, and the region 5 is of a P-type InP current narrowing layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a semiconductor laser device, and particularly to improvements in its current confinement layer.

[Conventional technology]

Figure 3(a) is an example of an engineering drawing republished optical communication device engineering P2.
40 is a conventional semiconductor laser device, and in the figure, +-11 is an n-type 1nP clad j-1121HI
nGaAsP active layer, (3) is P type 1nl'' cladding layer, (4) is P type 1nP current confining layer, 151in type 1n
P't; dl (7) is a dielectric insulating film, (8)
is the electrode metal.

In semiconductor lasers, n-type 1nP cladding layer (1)
electron and P-type cladding layer (31 holes I”t, In
It is implanted into the GaAsP active layer (2) and radiative recombination occurs.

When the fi of electrons and holes injected into the active layer, that is, the injected carrier density increases, the amount of light emission increases, leading to laser oscillation at the threshold current.

In the conventional semiconductor laser shown in Section 3 (a) IA, the P-type InP ML current narrows on both sides of the active layer J(!
+61, n-type 1nP current constriction layer (4) is made of InGa
The AsP active layer (21 was fabricated so as to be reverse biased when current was injected to have the effect of narrowing the t/f, and the InG
In addition to realizing high carrier density in the aAsP active layer (2) with a small current, by utilizing the difference in refractive index between InGaAsP and InP, light generated in the InGaA sP active layer (2) can be transferred to the InGaAaF' active layer (2). ) achieves efficient confinement.

Figure 4 is a cross-sectional view showing the conventional method for manufacturing the semiconductor laser shown in Figure 3. After forming a multilayer structure as shown in Figure 4 (a) and K, Dig 44 (Ill) on both sides of the active layer (2) as shown, and then
As shown in c), a P-type 1nP current confining layer (51a n
A semiconductor laser is formed by sequentially forming an InP type current constriction layer +41 and a P type 1nP buried layer Q21 to fill the groove.

In this method, a P-type 1nP current confining layer (61 is a P-type I
Also formed on the side of the nP cladding layer (3), a P-type InP cladding layer 13+, a P-type 1nP'5 flow confining layer II
, a leakage bus will inevitably occur due to the path of the n-type InP cladding layer fi+.

[Problem that the invention seeks to solve]

In the semiconductor laser device shown in FIG. 3(a), P-type In
P cladding layer +31, P type InP current narrowing layer 15
1. A leak path through the n-type 1nP cladding layer fi+ occurs as shown in Figure 3(b), which deteriorates the current confinement to the InGaA sP active layer (2) and It increases the value of current and also worsens the apparent current to light conversion efficiency.

This invention was made to solve the above-mentioned problems, and it effectively confines current to the active layer and reduces tt.
The object of the present invention is to provide a semiconductor laser device that can cause laser oscillation with current and efficiently convert current into light.

[Means for solving problems]

In the semiconductor laser device according to the present invention, the inner end of the third region forming the current confinement layer is located below the active region.

[Effect]

In the semiconductor laser device of the present invention, the inner end of the third region forming the current confinement layer is located below the active region, thereby eliminating reactive current flowing on both sides of the active layer.

[Embodiments of the invention]

An embodiment of the present invention will be explained below. 1st
The figure is a sectional view of a semiconductor laser device according to an embodiment of the present invention, viewed from the direction of the cavity end face.

In the figure, fil is an n-type InP cladding layer, (2) is InG
aAsP active layer, (3) is P-type 1nP cladding layer, (4
) is an n-type 1nP current confinement layer, (6) is a p-type 1nP @
It is a narrow layer.

FIG. 2 is a diagram showing the manufacturing method of the above embodiment. After forming a multilayer structure having an active layer (2) as shown in FIG. 2(-), an n-type 1 layer is formed as shown in FIG. 2(b).
nP cladding layer ill e InGaAsP active layer (2
) is etched in stripes. At this time, 1npH
After dissolving InP, etching can be accurately stopped at the P-type 1nP cladding layer (3) by using a sulfuric acid-based etchant that does not dissolve InP but dissolves InGaAIP. Next, as shown in FIG. 2(c), both sides of the active layer (6) and the n-type 1nP cladding layer +11
After covering the active layer with a mask, side etching is performed until the P-type 1nP cladding layer below the active layer (21) becomes narrower than the active layer, as shown in FIG. 2(d).

At this time, by using a hydrochloric acid-based etching solution, which is an etchant that dissolves InP but not InGaAaP, an active 1i1 (31
It retained its shape! ! P-type InP cladding layer (3)
can be etched.

Next, an InP multilayer crystal is grown in the groove part (river) formed so that the lower part of the active layer is particularly narrow as shown in FIGS. 2(e), (f) and Ic. ,)
As shown in FIG. 2, in the liquid phase growth method, a P-type I+P layer i91 and an n-type 1nP current width 1m+41 are grown under the InGaAsP active layer (3) using the characteristic that growth is easier in concave portions than in convex portions. Next, as shown in FIG. 2(f)K, a P-type 1nP current constricting layer (61) and an n-type 1nP buried layer α are sequentially grown to completely fill the trench. After that, an electrode is formed, and an electrode is formed at the center of the trench. By separating, the semiconductor laser device shown in FIG. 1 is obtained.

In the semiconductor laser device manufactured according to this example, as is clear from FIG. The type 1nP cladding layer (1) and the n-type 1nP current confining layer (4) can be completely separated, and as a result, it is possible to eliminate the reactive current that does not contribute to light emission flowing on both sides of the InGaAsP active layer (2). Done,
It becomes possible to achieve low threshold and high efficiency.

〔Effect of the invention〕

As described above, according to the present invention, since the inner end of the third region forming the current confinement layer is located below the active region, a semiconductor laser device with a low threshold value and high efficiency can be obtained. effective.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the present invention, and is a sectional view showing a semiconductor laser device, and FIG. 2 (a), (b), (c), and (d).
(e) (r)uIt is a sectional view by process which shows the manufacturing method. 3 (,) (b) is a cross-sectional view showing a conventional semiconductor laser device, and FIG. 4 is a cross-sectional view showing a conventional manufacturing method by step. (21L
f'X I nGaA@P active layer, (3) is P type 1nP
Cladding layer, (4) is n-type InP current confinement layer, (6)
is a P-type 1nP reflux constriction layer, and (11) is a groove formed in the multilayer structure. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] a first region of a first conductivity type; an active region of a predetermined width that makes a junction with the first region; a second region of a second conductivity type that makes a junction with the active region; a third region of the second conductivity type in contact with the second conductivity type, and a fourth region forming a pn junction with the third region, the first region;
A semiconductor laser device characterized in that a current confining layer is formed by the third region and the fourth region, and an inner end of the third region forming the current confining layer is located below the active region. .