JP2755721B2 - Semiconductor crystal growth method - Google Patents

Description

The present invention relates to a method for growing a semiconductor crystal, and more particularly, to a method for epitaxially growing a chalcogenide crystal containing p-type zinc and / or cadmium. .

(Prior Art) A chalcogenide crystal containing zinc or cadmium or both has difficulty in controlling the electric conduction type. Above all, it is very difficult to obtain p-type conductive crystals of zinc sulfide (ZnS), zinc selenide (ZnSe), and a mixed crystal of these materials, zinc sulphide (ZnSe), which are attracting attention as visible light emitting element materials. Cadmium sulfide (CdS), cadmium selenide (CdSe), and cadmium zinc sulfide (ZnCd
The same applies to S). For bulk single crystal ZnSe,
Nishizawa et al. Reported a p-type crystal. However, although p-type ZnS or ZnSe crystals formed by epitaxial growth have been reported by a few research institutions, no satisfactory controllability and reproducibility have yet been obtained.
For example, regarding epitaxial growth of a p-type zinc chalcogenide crystal using a group III-V semiconductor crystal substrate, Hiiragimoto et al. Reported that a p-type crystal was obtained using lithium nitride as a dopant. Shibata et al. Also reported that p-type ZnSe crystals were obtained by MOCVD using ammonia as a dopant. However, at present, p-type crystals with good controllability have not been obtained by any of the methods.

Investigation into the cause reveals that in the growth of a II-VI compound crystal of a chalcogenide of zinc or cadmium on a III-V crystal substrate, the group III element from the substrate diffuses into the epitaxial layer and becomes a donor as an acceptor. The fact that it compensated for it became clear. Then, it was found that the crystal growth was performed under a very unstable condition of showing or not showing p-type due to a slight difference in growth conditions.

(Problems to be Solved by the Invention) As described above, conventionally, there has been a problem that it is impossible to epitaxially grow a p-type zinc chalcogenide or cadmium chalcogenide crystal with controllability and reproducibility sufficient for practical use.

The present invention has been made in view of the above points, and has as its object to provide a method for epitaxially growing a p-type chalcogenide crystal containing zinc or cadmium or both with good controllability and reproducibility.

[Constitution of the Invention] (Means for Solving the Problems) In the present invention, a p-type chalcogenide crystal to which nitrogen is added is grown on a semiconductor crystal substrate under a condition in which zinc or cadmium or both of them are supplied in excess. It is characterized by the following.

(Effect) According to the present invention, the crystal growth is performed under the condition that the supply amount of zinc or cadmium or both of them is excessive, so that the group VI element position constituting the chalcogenide crystal containing zinc or cadmium or both can be obtained. Effectively, nitrogen is easily taken in. As a result, a p-type chalcogenide crystal can be obtained with good reproducibility and controllability. In particular, when a GaAs, GaP, InAs or a mixed crystal III-V crystal substrate is used as the substrate, zinc or cadmium or both of them are oversupplied from the substrate to the zinc or cadmium lattice position under the condition of excessive supply of zinc or cadmium. III
Diffusion of group element is suppressed, and a good p-type chalcogenide crystal is obtained.

(Example) Hereinafter, an example of the present invention will be described.

FIG. 1 shows zinc sulfide (Zn) used in one embodiment of the present invention.
S) This is an apparatus for epitaxially growing ZnS crystals by a hydrogen (H ₂ ) transport method using powder as a raw material. ZnS powder 11 and the substrate 12 as a raw material is placed in a reaction furnace 14, a ZnS powder 11 and the Zn and S are adapted to be transported to the installation position of the substrate 12 by equivalent by H _2. In the reactor 14, NH was used as a dopant.
₃ gas can be supplied from outside. Apart from the raw material powder, metal Zn13 is placed near it, from here
It is also configured so that Zn partial pressure can be applied by transporting Zn to the substrate mounting portion also with H ₂ .

An example of the growth conditions when an n-type GaAs substrate is used as the substrate 12 is shown in the table below.

FIG. 2 shows the temperature distribution in the reactor during the growth.

By giving a condition of excessive Zn supply under the above conditions, the N-doped p-type ZnS crystal layer 6 could be epitaxially grown on the n-type GaAs substrate 15 as shown in FIG.

FIG. 4 shows the results of measuring the electric conductivity type and the resistivity of the obtained ZnS crystal when the Zn partial pressure was changed in the above example. If not adding Zn partial pressure, NH ₃ when no additive showed a low resistance n-type 10 [Omega · cm, show no p-type a high resistance n-type be added NH _3. On the other hand, when the Zn partial pressure is applied, p-type conduction is exhibited with an increase in the supply amount of Zn, and the resistivity also decreases as shown in the figure. By giving a condition of excess Zn supply, N, which is a p-type impurity, is effectively replaced and taken into the group VI position, and diffusion of Ga, which is a donor impurity, from the substrate to the growth layer is effectively performed. By being suppressed, a good p-type crystal can be obtained.

Similarly, an N-doped p-type ZnS crystal could be epitaxially grown on a p-type GaAs substrate under the condition of excess Zn supply.

By performing epitaxial growth under the same conditions using ZnSe powder or polycrystal as a raw material, it was possible to epitaxially grow p-type ZnSe crystals on n-type and p-type GaAs substrates also under the condition of excess Zn supply.

By performing epitaxial growth under the same conditions using CdS powder or polycrystal as a raw material, p-type CdS crystals could be epitaxially grown on n-type and p-type GaAs substrates also under the condition of excess Cd supply.

FIG. 5 shows a growth apparatus of another embodiment utilizing the MOCVD method. Reference numeral 21 denotes a dimethyl zinc supply unit, 22 denotes a dimethyl selenium supply unit, 23 denotes a quartz reaction tube, 24 denotes an induction heating device, and 25 denotes a substrate installation unit. By using this MOCVD apparatus, the Zn partial pressure is controlled by the supply amount of dimethyl zinc, and ZnSe crystals are grown under the condition that the Zn supply amount is excessive. NH when the Zn supply is small
_Although p-type ZnSe crystal was not obtained even when ₃ was added, a good p-type ZnSe crystal could be epitaxially grown on an n-type GaAs substrate by using an excessive amount of Zn as in the previous example. .

The invention is equally applicable to the MBE method. When the same crystal growth is performed by the MBE method, Zn and Se are used as raw materials, and the beam pressure is set to an excessive Zn condition. NH ₃ is introduced into the substrate as an N material. Thereby, a p-type ZnSe crystal can be obtained with good reproducibility. At this time, the doping efficiency can be increased by preheating or ionizing NH ₃ .

It is also possible to continuously grow an n-type ZnS crystal and a p-type ZnS crystal using the growth apparatus of FIG. As shown in FIG. 6, using an n-type GaAs substrate 33, first, without adding NH ₃ ,
The n-type ZnS crystal layer 32 is grown under the condition that no n partial pressure is applied.
In the middle of growth, add a partial pressure of Zn and add NH ₃ ,
A p-type ZnS crystal layer 33 is grown.

FIG. 7 shows the relationship between the growth thickness, the electric conductivity type and the carrier concentration distribution at this time. Thus, according to this embodiment, a good pn junction of ZnS can be obtained.

First, on a p-type GaAs substrate, p-type Zn
It is similarly possible to grow an S crystal and subsequently grow an n-type ZnS crystal to obtain a pn junction.

The present invention is not limited to the above embodiment. For example, in addition to GaAs, other semiconductor crystals such as GaP, InAs or a mixed crystal thereof can be used as the substrate. Zinc chalcogenides to be grown are generally ZnS _x Se _1-x , ZnS _x Se _y Te
_1-xy etc., and cadmium chalcogenide is represented by CdS _x Se _1-x , CdS _x Se _y Te _1-xy ,
Furthermore, these mixed crystal chalcogenides are Zn _x Cd _1-x S _y Se _1-y , Zn
_x Cd _1-x Se _y Te _{1- y} etc.By selecting their composition ratio, it is possible to eliminate lattice mismatch with the substrate and obtain a good crystal. it can.

In addition, the present invention can be variously modified and implemented without departing from the spirit thereof.

[Effects of the Invention] As described above, according to the present invention, a p-type zinc chalcogenide or cadmium chalcogenide or a mixed crystal chalcogenide doped with nitrogen is grown on a semiconductor crystal substrate with good controllability and reproducibility. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a vapor phase growth apparatus used in one embodiment of the present invention, FIG. 2 is a diagram showing a temperature distribution of the growth furnace, and FIG. 3 is a diagram showing an epitaxial substrate obtained by the embodiment. FIG. 4 is a diagram showing a relationship between Zn partial pressure and electric conductivity and resistivity, FIG. 5 is a diagram showing a MOCVD apparatus used in another embodiment, and FIG. 6 is a diagram showing an epitaxial substrate according to another embodiment. FIG. 7 is a diagram showing a carrier concentration distribution of the epitaxial growth layer. 11: ZnS powder, 12: Substrate, 13: Metal Zn, 14: Reactor, 15: n-type GaAs substrate, 16: p-type ZnS crystal layer, 21
... Dimethyl zinc supply unit, 22 ... Dimethyl selenium supply unit, 23 ... Quartz reaction tube, 24 ... Induction heating device, 25 ... Substrate installation unit, 31 ... N-type GaAs substrate, 32 ... N-type ZnS Crystal layer, 33... P-type ZnS crystal layer.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hitoshi Kanto 5-9-1-2 Shimoyama, Nagaoka City, Niigata Prefecture (56) References JP-A-60-204698 (JP, A)

Claims (5)

(57) [Claims] The present invention is characterized in that a chalcogenide crystal containing nitrogen-added zinc or cadmium or both is grown on a semiconductor crystal substrate under conditions of excess supply of zinc and / or cadmium. A method for growing a semiconductor crystal. 2. n containing Ga or In or both of them.
Under the condition of excess supply of zinc or cadmium or both on a III-V compound semiconductor substrate of the type
A method for growing a semiconductor crystal, comprising growing a p-type or lucogenide crystal containing nitrogen-added zinc or cadmium or both. 3. A p-type containing Ga or In or both of them.
Under the condition of excess supply of zinc or cadmium or both on a III-V compound semiconductor substrate of the type
A method for growing a semiconductor crystal, comprising growing a p-type chalcogenide crystal containing nitrogen-added zinc, cadmium, or both. 4. An n-type group III-V compound semiconductor substrate containing Ga or In or both of them, an n-type chalcogenide crystal containing zinc or cadmium or both is grown, and then zinc or cadmium or Under conditions of overfeeding both of these, p-containing zinc or cadmium or both
A method for growing a semiconductor crystal, comprising growing a type chalcogenide crystal. 5. A method according to claim 1, wherein the p-type group III-V compound semiconductor substrate containing Ga or In or both of them contains zinc and / or cadmium and nitrogen-added zinc and / or cadmium. A method for growing a semiconductor crystal, comprising growing a p-type chalcogenide crystal containing cadmium or both, and subsequently growing an n-type chalcogenide crystal containing zinc, cadmium or both.