JPH0435080A - Burried semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent deterioration of element and to improve characteristics and reliability of element by forming a high resistance GaInP, having impurity concentration of 1X10<17>cm<-3> or above and commensurates in lattice with GaAs, in contact with mesa stripe side face including a double-hetero structure. CONSTITUTION:When carbon or iron is doped with concentration of 1X10<17>cm<-3> or above, superlattice structure is randomized and the value of Eg is maximized. Consequently, undoped growth takes place on a GaAs substrate to commensurate the lattices. It has same composition as GaInP. A mesa stripe side face having double-hetero (DH) structure is then burried into a high resistance crystal having impurity concentration of 1X10<17>cm<-3> or above. Consequently, a structure burried with a DH active layer having Eg, higher by upto 90mev, can be obtained. Since the burried layer in commensurates in lattice with GaAs substrate, no defect is introduced from the interface thus protecting the characteristics and reliability of laser element against detectioration.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a visible light semiconductor laser, and more particularly to a buried semiconductor laser with transverse mode control.

(Prior Art) An A, Q GaInP semiconductor laser lattice-matched to a GaAs substrate oscillates in the visible light range of wavelengths 580 to 690 n11, and its importance has increased particularly in recent years.

The prior art will be explained using the schematic diagram of the laser structure shown in FIG. On the n-GaAs substrate 101, H(
A, Il O,6Gao, + )6.5 I n6,5
P cladding layer 102, undoped (AJI O, I7
Gao, ai) o, s I n o, 5 P active layer 203, p (A, Il O, 6 Gao, 4) (+
, 91 n, o, sP cladding layer 104, p - Ga
The outer side of the mesa stripe made of As layer 105 is iron-doped insulating Ga. , r I no, i has an embedded type embedded by P2O3. Buried layer 20
8 has a bandgap energy (E
g) is sufficiently large and has a high resistance, so the buried layer 208 has the effect of confining injected carriers and light.

In addition, compared to the case where the buried layer 208 in FIG. 3 is ternary, compared to the case where it is buried with a quaternary mixed crystal A or QGaTnP containing A and 0, the layer structure of FIG. 3 reduces the thermal resistance. Furthermore, since it does not contain Aj, element deterioration due to AfJ can be avoided (Japanese Patent Application No. 19832/1983).

(Problem to be Solved by the Invention) In the conventional semiconductor laser described above, the buried layer 208
Since it is not lattice matched with the substrate 1.01, defects such as lattice defects are likely to be introduced into the buried interface, and these defects impair the device characteristics and device reliability of the semiconductor laser. Further, if the energy gap difference between the active layer and the buried layer is large, the refractive index difference will also be large, and if the stripe width is as wide as about 3 to 10 μm, higher-order transverse modes are likely to occur. If an attempt is made to reduce the compositional difference between the active layer and the buried layer in order to reduce the refractive index difference in order to prevent this, it will be difficult to control the composition in manufacturing.

The purpose of the present invention is to reduce the thermal resistance in the same manner as conventional semiconductor lasers without impairing the inherent functions of the buried heterostructure, to avoid deterioration due to Aj, and to avoid defects at the buried interface so that the device Our goal is to provide semiconductor lasers with excellent characteristics and reliability.

Furthermore, the present invention reduces the relative refractive index difference between the active layer and the buried layer to 1
Another object of the present invention is to provide a semiconductor laser that can be set to a small value of 0-2 to 10 with good controllability and that can easily maintain the fundamental transverse mode.

(Means for Solving the Problems) The present invention provides means for solving the problems remaining in the conventional techniques described above.
1) GaInP that is approximately lattice-matched to a GaAs substrate whose main surface is a plane equivalent to the (001,) plane, a plane tilted by an angle of within 10° from the (001,) plane, or a plane equivalent to the tilted plane.
A double heterostructure having an active layer and a cladding layer of AlGaInP or AJTnP having a larger energy gap than the active layer is formed in a stripe shape on the main surface of the GaAs substrate, and a stripe shape including the double heterostructure is formed on the main surface of the GaAs substrate. It is in contact with the mesa side surface of the GaAs substrate, is almost lattice matched with the GaAs substrate, and has an impurity concentration of 1×1017(2)-
This is a buried semiconductor laser characterized in that a high resistance G a I n P layer having a resistance of 3 or more is formed.

(Function) Even if the composition of G a T n P is constant, it has different Eg values depending on the growth conditions (FIG. 2). G like this
The Eg value of aInP differs depending on the growth conditions, including the growth temperature, the ratio of Group II raw material to Group V raw material during growth, and V/II.
This is because the atomic arrangement state of the crystal in the mixed crystal differs depending on the growth conditions such as the I ratio. In other words, group ■ atoms (Ga, In
) or are arranged randomly on the sublattice, and group (III) atoms are arranged alternately on the (11,1) plane or (111) plane (including equivalent planes) on the sublattice, either on the Ga plane or the In plane. Eg is different depending on the case with a superlattice arrangement. Maximum E in random state
In a superlattice arrangement state with regularity, Eg becomes smaller by about 901+leV than in the random case.

This superlattice arrangement state allows impurities such as carbon and iron to be
When doped to a concentration of 0'''(1)1 or more, randomization occurs and the Eg value becomes the highest (Figure 2).

Therefore, a double hetero (DH) structure is formed using a high-resistance crystal that is grown to be lattice-matched to the GaAs substrate with AND-1, has the same composition as GaInP, and has an impurity concentration of 1×1017 CI11-3 or more. By embedding the side surface of the mesa stripe having a 0.25 mV, it is possible to obtain a structure in which the DH active layer is buried in a layer with an Eg higher than the Eg of the DH active layer by up to 90 mev. In the structure of the present invention,
Since the buried layer is lattice-matched to the GaAs substrate and does not contain AfJ, defects are not introduced from the buried interface, etc., and deterioration of laser device characteristics and reliability can be reduced.

(Example) The present invention will be described below with reference to an example shown in FIG.

FIG. 1 is a side view of the embodiment viewed from the resonator end face side. The stripes run perpendicular to the page. In manufacturing this example, first, n-(A, Q) is formed on the nGaAsM plate 101.

Gao, +) o, s T no, s P cladding layer 102, undoped (AfJo, +tGao, ai)
o, s I no, P active layer 103, P (A, OO
, 6Gao, 4) o, 5Ino, the sP cladding layer 104, and the p-GaAs layer 105 are sequentially grown epitaxially. As for growth.

Here, the MOCVD method, which is excellent in mass production and reproducibility, was used. SL, 2 was adhered to the surface of the epitaxial layer, and no Sin was left in a stripe pattern by photophosphorography. For the GaAs layer, use a mixture of sulfuric acid/hydrogen peroxide/water as an etching solution, and for the AJGaTnP layer, use dilute hydrochloric acid as the etching solution to remove the portion of the epitaxial layer that is not covered with SiO□. , forming mesa-like stripes. Subsequently, Ga doped with impurity concentration 1×1018 CII13 iron was formed again by MOCVD method.
Grow o, s I no, s P 108. Second
From the figure, the energy gap Eg of Gao, s I no, and s P is 1.91 eV, which is 0.09 eV larger than the 1.83 eV of undoped Gao, s I no, and s P in the active layer. This is a sufficiently large EgO difference. At this time, on the surface of SiO□, G
a a, 5Ino, sP does not grow, and iron-doped insulating Gao, sIno, sP does not grow in the area where there is no SiO□.
108 is grown to embed the mesa-like stripes to form a buried heterostructure. Thereafter, SiO□ is removed with hydrochloric acid to form a p-electrode 106 of T i /P t /A u and an n-electrode 107 of A u /G e to form a device.

This example uses G, which has a large lattice mismatch with the GaAs substrate.
Compared to a semiconductor laser embedded with ao, 7I no, i P or a semiconductor laser embedded with a semiconductor layer containing A, 0, the device characteristics and reliability are excellent.

In this embodiment, the insulating layer is used for burying, but the same effect can be obtained even if the Pn inversion layer is used for burying.

In addition, I X 10 l7an- on the side of the mesa stripe
A similar effect can be obtained by contacting a high resistance layer having an impurity concentration of 1 or more and then embedding an A, 0 GaInP layer with a high Eg.

(Effects of the Invention) By employing the configuration of the present invention as described above, element deterioration can be avoided, and the element characteristics and reliability can be significantly improved compared to conventional semiconductor lasers.

[Brief explanation of drawings]

FIG. 1 is a side view of an embodiment of the present invention viewed from the resonator end face side, and FIG. 2 is a diagram showing undoped Ga. Tno, the growth temperature of the band gap energy (Eg) of sP, and the ratio of group ■ to group V of the raw material during growth,
3 is a side view of a conventional semiconductor laser. FIG. 3 is a side view of a conventional semiconductor laser. In the figure, 101 is an n-GaAs substrate, 102 is an n(Aj O
, 6Gao, +) o, T no, s P cladding layer, 103 is undoped Gao, s I no, s P active layer, 104 is p (A, OO, 6Gao, < )
o51 no, sP cladding layer, 105 is p-GaAs
Cap layer, 106 is P electrode, 107 is N electrode, 108
is insulating Gao, s I no, s P, 109 is insulating (A, llO, 6G ao, +) o, s I n
o, s P, 203 is undoped (A, llo, +yG
ao, ai) o, s T no, s P active layer, 20
8 indicates insulating Gao7I no and 3P, respectively.

Claims (1)

[Claims] Approximately lattice-matched to a GaAs substrate whose main surface is a (001) plane, a plane equivalent to the (001) plane, a plane tilted by an angle of within 10 degrees from the (001) plane, or a plane equivalent to the tilted plane. GaInP is used as an active layer, and AlGaInP or A has a larger energy gap than this active layer.
The double heterostructure with lInP as the cladding layer is the G
It is formed in a stripe shape on the main surface of the aAs substrate,
In contact with the side surface of the striped mesa including the double heterostructure, a high-resistance G layer is substantially lattice-matched with the GaAs substrate and has an impurity concentration of 1 x 10^1^7 cm^-^3 or more.
A buried semiconductor laser characterized in that an aInP layer is formed.