JP2929632B2 - Optical device manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an optical device, and is particularly suitable for application to the manufacture of an optical device using a wide gap semiconductor.

[Summary of the Invention]

The present invention relates to a method for manufacturing an optical device, comprising: forming a compound semiconductor layer doped with an n-type impurity on a semiconductor substrate, and then introducing hydrogen into the compound semiconductor layer, thereby doping the compound by doping the n-type impurity. By including a step of deactivating an acceptor formed in a semiconductor layer, a semiconductor laser or a light-emitting diode in a short wavelength band having good characteristics can be realized.

[Conventional technology]

The wavelength of semiconductor lasers has been shortened from GaAs / AlGaAs (Ga: gallium, As: arsenic, Al: aluminum) based semiconductor lasers with wavelengths up to 800 nm, to InGaP / AlGaInP (In: indium, P: phosphorus) based semiconductor lasers. 650nm wavelength. And in recent years, the wavelength 400
Attempts are being actively made to realize a short-wavelength semiconductor laser capable of outputting light in the blue band of up to 500 nm. Among the semiconductor materials expected to emit light in the blue band, ZnTe (Zn: zinc, Te: tellurium) and MgTe (Mg:
Magnesium) and BeTe (Be: beryllium).

[Problems to be solved by the invention]

Incidentally, formation of a good pn junction is important for realizing a semiconductor laser. However, the above-mentioned ZnTe, MgTe, BeTe
And the like, the energy gap is large, so that even if donor impurities (n-type impurities) are introduced into them to make them n-type, it is difficult to obtain an n-type due to a so-called self-compensation effect. It is.

The self-compensation effect will be described in more detail with reference to ZnTe as an example. That is, as shown in FIG. 3, when the ZnTe crystal is doped with, for example, gallium (Ga) as a donor impurity, the doping of Ga causes the Zn to be doped.
A vacancy _Vzn ^{+ of} Zn serving as an acceptor is formed in the Te crystal, and Ga as a donor impurity and the vacancy _Vzn ⁺ form a stable donor-acceptor pair. And ZnTe
Of the three valence electrons of Ga atoms doped into the crystal, one electron that is not used for bonding with an adjacent Te atom is a vacancy V _zn ⁺
And not a carrier. Thus, ZnTe
The vacancy V _zn ⁺ induced by doping the crystal with Ga acts as an acceptor, and as a result, Ga does not act as a donor, which is why it is difficult to obtain n-type ZnTe. The same can be said for MgTe and BeTe.

As described above, ZnTe, MgTe, BeTe, and the like are semiconductor materials that are expected to emit light in the blue band, but it is difficult to obtain an n-type material due to the self-compensation effect. It was difficult to form a good pn junction. For this reason, it has been difficult to realize a semiconductor laser in a short wavelength band having good characteristics. This applies not only to semiconductor lasers but also to light emitting diodes.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing an optical device capable of realizing a semiconductor laser, a light emitting diode, or the like in a short wavelength band having good characteristics.

[Means for solving the problem]

According to the findings of the present inventors, hydrogen (H) can penetrate deeply into a semiconductor because its atomic radius is small,
Moreover, when the conductivity type of the base semiconductor is p-type, almost H
One atom can deactivate one acceptor. For example, when the acceptor concentration is 1 × 10 ¹⁸ / cm ³ , by introducing about 10 ¹⁸ to 10 ¹⁹ / cm ³ of H,
The p-type conductivity can be almost completely canceled.

The present invention has been devised based on the above findings of the present inventors.

That is, the present invention provides a method for manufacturing an optical device, comprising: forming a compound semiconductor layer (3) doped with an n-type impurity on a semiconductor substrate (1);
A step of deactivating acceptors formed in the compound semiconductor layer (3) by doping n-type impurities by introducing hydrogen therein.

Here, the compound semiconductor layer (3) may be any compound semiconductor layer having a wide gap where it was difficult to obtain an n-type compound semiconductor layer due to a self-compensation effect. Specifically, this compound semiconductor layer (3) is made of a II-VI group compound semiconductor such as ZnTe, MgTe, BeTe, etc., and chalcopyrite (I-III-VI group ₂ compound semiconductor, II-IV-V _{2 group).} CuGaS ₂ (Cu: copper, S: sulfur), which is one of group compound semiconductors, may be used. Here, CuGaS ₂ has an energy gap
It is a 2.4 eV direct transition type semiconductor, and is a light emitting device material expected to have high luminous efficiency in the blue band.

As a method for introducing hydrogen into the compound semiconductor layer (3), for example, a hydrogen plasma treatment can be used. Further, for example, a silicon nitride film containing hydrogen is formed so as to cover the compound semiconductor layer (3) by a plasma CVD method,
Thereafter, a method of introducing hydrogen in the silicon nitride film into the compound semiconductor layer (3) by performing a heat treatment can also be used.

[Action]

According to the method for manufacturing an optical device of the present invention configured as described above, by introducing hydrogen into the compound semiconductor layer (3) doped with the n-type impurity, the compound semiconductor layer is doped with the n-type impurity. (3) The acceptor formed therein can be deactivated. For this reason, the n-type impurity doped in the compound semiconductor layer (3) acts as a donor, and although it has a wide gap, it is difficult to obtain an n-type compound due to the self-compensation effect. As for 3), an n-type can be obtained. Therefore, for example, by using the semiconductor substrate (1) on which the p-type compound semiconductor layer (2) is formed in advance, a good pn junction can be easily formed. As a result, it becomes possible to realize a semiconductor laser, a light emitting diode, or the like in a short wavelength band having good characteristics.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. This embodiment is an embodiment in which the present invention is applied to the manufacture of a semiconductor laser (or laser diode) using ZnTe.

In this embodiment, as shown in FIG. 1A, first, a p-type ZnTe layer 2 is formed on a p-type semiconductor substrate 1, and then Ga is doped on the p-type ZnTe layer 2 as an n-type impurity. Was
A ZnTe layer 3 is formed. In this state, as described above, the Ga-doped ZnTe layer 3 is not n-type due to the self-compensation effect (see FIG. 3). Here, the semiconductor substrate 1
For example, a material that lattice-matches with ZnTe, such as an InAs substrate, is preferably used. In addition, these p-type ZnTe layers 2
The Ga-doped ZnTe layer 3 can be formed by, for example, a molecular beam epitaxy (MBE) method.

Next, for example, by hydrogen plasma treatment, Ga-doped ZnTe
Inject H into layer 3. Here, it is preferable that the implantation amount of H is at least equal to the doping amount of Ga in the Ga-doped ZnTe layer 3. Thus, as shown in FIG.
In the Ga-doped ZnTe layer 3 into which the atoms have been implanted, the electrons of the H atoms are bound to the vacancies V _zn ⁺ as acceptors formed in the Ga-doped ZnTe layer 3 by doping with Ga, whereby the vacancies V _zn ⁺ neutralizes. That is, vacancies V acting as acceptors in the Ga-doped ZnTe layer 3 by the implantation of H
_zn ⁺ will be deactivated. As a result, Ga-doped Z
Ga in the nTe layer 3 acts as a donor, and an n-type ZnTe layer 4 is formed as shown in FIG. 1B. And
A pn junction is formed by the p-type ZnTe layer 2 formed earlier and the n-type ZnTe layer 4. Since the efficiency of deactivation of the acceptor by H is very high, the concentration of Ga actually acting as a donor in the n-type ZnTe layer 4 is determined by the concentration of Ga doped first.
Is almost the same as

After that, according to the standard manufacturing method of semiconductor laser,
Fig. 1 C
As shown in (1), a target ZnTe-based semiconductor laser is completed. In FIG. 1C, reference numerals 5 and 6 indicate ohmic electrodes. In the semiconductor laser shown in FIG. 1C, a blue laser beam is output by flowing a forward current through a pn junction composed of the p-type ZnTe layer 2 and the n-type ZnTe layer 4.

As described above, according to this embodiment, H is implanted into the Ga-doped ZnTe layer 3, so that
The vacancies V _zn ⁺ acting as acceptors in the ZnTe layer 3 can be inactivated by the implanted H atoms, so that the n-type ZnTe layer 4 which has been difficult to obtain conventionally can be easily obtained. . Thereby, the p-type ZnTe layer 2 and the n-type ZnTe layer 4
Thus, a good pn junction can be obtained, and a short-wavelength semiconductor laser capable of emitting blue light having good characteristics can be realized.

Further, since the deactivation of the acceptor (V _zn ⁺ ) by the above-mentioned H atom is not in a metastable state, even if annealing is performed after this deactivation, the acceptor (V _zn ⁺ ) is activated again. Therefore, it is convenient for manufacturing a semiconductor laser.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible.

For example, in the above embodiment, ZnTe has been described. However, by adding a small amount of S to ZnTe to form ZnTeS, the wavelength can be further shortened. In the above embodiment, the p-type ZnTe layer 2 and the Ga-doped ZnTe layer 3 are formed by the MBE method, but they can also be formed by the metal organic chemical vapor deposition (MOCVD) method. .
As an n-type impurity for ZnTe, for example, B (boron), In, or the like can be used instead of Ga.

Further, in the above-described embodiment, the case where the present invention is applied to the manufacture of a semiconductor laser using ZnTe has been described.However, the present invention can be applied to the manufacture of a semiconductor laser using a wide gap semiconductor other than ZnTe. Needless to say, this is possible. Although the ZnTe-based semiconductor laser of the above-described embodiment has a single homojunction, the present invention can also be applied to the manufacture of a double heterojunction semiconductor laser. Instead, the present invention can be applied to a light emitting diode. By using such a light emitting diode capable of emitting blue light, for example, a flat color display can be manufactured using a semiconductor.
Moreover, this flat color display can be manufactured with a high precision of μm or less by using the LSI manufacturing technology already established.

〔The invention's effect〕

As described above, according to the present invention, after a compound semiconductor layer doped with an n-type impurity is formed on a semiconductor substrate, hydrogen is introduced into the compound semiconductor layer, whereby the n-type impurity is doped. Since the method includes a step of deactivating an acceptor formed in the compound semiconductor layer, it is difficult to obtain an n-type compound semiconductor layer due to a self-compensation effect despite a wide gap.
You can get a type. As a result, it becomes possible to realize a semiconductor laser, a light emitting diode, or the like in a short wavelength band having good characteristics.

[Brief description of the drawings]

1A to 1C are cross-sectional views for explaining a method of manufacturing a semiconductor laser according to an embodiment of the present invention in the order of steps, and FIG. 2 is a diagram showing n-type Zn by injecting H into a Ga-doped ZnTe layer.
FIG. 3 is an explanatory diagram for explaining a mechanism for obtaining a Te layer, and FIG. 3 is an explanatory diagram for explaining a self-compensation effect. Explanation of main symbols in the drawings 1: semiconductor substrate, 2: p-type ZnTe layer, 3: Ga-doped ZnTe layer, 4: n-type
ZnTe layer.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H01S 3/18 H01L 33/00

Claims (1)

(57) [Claims] An n-type impurity-doped compound semiconductor layer is formed on a semiconductor substrate, and then hydrogen is introduced into the compound semiconductor layer, whereby the n-type impurity is doped into the compound semiconductor layer. A method for manufacturing an optical element, comprising a step of deactivating a formed acceptor.