JP2828979B2 - Crystal growth method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a crystal growth method. This method is used for a semiconductor device using a heterojunction such as a semiconductor laser device. [Prior Art] There are two crystal structures of a compound semiconductor and a mixed crystal semiconductor thereof, a zinc blende type and a wurtzite type, but most of crystals actually used in semiconductor devices are the zinc blende type.
On the other hand, many wurtzite crystals have a wide band gap and are expected as materials for visible light lasers and the like. However, when designing a device by combining materials having these crystal structures, it is particularly difficult to fabricate a good heterojunction without stacking faults due to the difference in the structure (11).
1) It is impossible and extremely feasible at the joint surface other than the surface. An example of this is shown in the Abstracts of the Japan Society of Applied Physics Spring 82, p748 Motohiro Hiiragi. [Problems to be Solved by the Invention] FIGS. 1 and 2 show crystal structures of sphalerite and wurtzite. Consider the case where a wurtzite-type crystal is hetero-joined on the (100) plane of a zinc-blende-type crystal. The bonding surface of the zinc-blende-type crystal has an atomic arrangement as shown in FIG. Such a crystal arrangement does not have a plane having such an atomic arrangement, and a coherent heterojunction cannot be formed. An object of the present invention is to enable a heterojunction between substances having originally different crystal structures. [Means for Solving the Problems] The object of the present invention is to provide a desired atomic layer epitaxy growth method (Atomic layer) in which anions and cations are alternately and temporally supplied to a solid phase crystal growth interface to grow crystals one atomic layer at a time.
Layer Epitaxy; hereinafter abbreviated as ALE method. By using (), it becomes possible and possible to change the crystal structure of the epitaxial layer to the same as the crystal structure of the substrate. [Effect] Both the sphalerite structure and the wurtzite structure have a tetrahedral coordination, and the difference is merely that the position of the second nearest atom is rotated by 60 degrees as shown in FIG. The difference in free energy in each structure is not so large, and there is no significant difference in its stability. In fact, ZnS, CdS, BN, etc. have both crystal structures. The energy band structure is also determined mainly by the interaction between the closest atoms, so that there is no significant difference between the two crystal structures. In the case of ZnS, both sphalerite and wurtzite are direct transition types, and the bandgap is 3.6 eV and 3.8 eV, respectively. As shown in FIG. 1, the (100) plane of the sphalerite-type crystal has monolayers of anions and cations alternately stacked.
Considering the case where the surface of the (100) plane is formed by anions, when a cation of a material originally having a wurtzite structure reaches this surface, a bond having a wurtzite structure has appeared. Since it does not exist, it is taken into the lattice position of the cation of the sphalerite structure. In this way, by supplying anions and cations alternately to the growth interface over time, a wurtzite type is originally changed to a zincblende type, which is a crystal structure of a substrate, and a good hetero bond becomes possible. Embodiment An embodiment of the present invention will be described below with reference to FIG. 51 is a (100) GaAs substrate having a zinc-blende structure, 52 is a GaAs buffer layer adjusted by the ALE method so that the heterojunction surface becomes a uniform anion surface (or cation surface) over the entire wafer,
53 ALE Cd _0.58 Zn _0.42 S with bond length equal to GaAs
It is an epitaxial layer grown by a method. 52 and 53
Was grown continuously by the ALE system, which is basically an MBE system with an enhanced exhaust system. As a result of structural analysis of the epitaxy layer by X-ray diffraction, it was found that the layer had a zinc blende type structure. In the present embodiment, the epitaxial layer is mixed when supplying the group II atoms, and Cd _0.58 Zn _0.42 S
Although a crystalline semiconductor was used, for example, (CdS), (ZnS), (CdS
A superlattice semiconductor in which S), (ZnS), (CdS), (ZnS), (CdS), and (CdS) have one cycle may be used. FIG. 6 is a sectional view of a wafer having a double hetero structure grown by using the present invention. 61 is a GaAs substrate, 62 is Ga
As buffer layer (0.1 μm), 63 is a Cd _0.58 Zn _0.42 S cladding layer (1 μm), and 64 is a GaAs active layer (0.1 μm).
Laser light from the GaAs active layer could be observed by cleaving this wafer to 30 × 250 μm ² and photoexciting it with a 5145 ° argon ion laser. Table 1 shows an example of a combination of a substrate and an epitaxial layer capable of forming a heterojunction according to the present invention. [Effects of the Invention] According to the present invention, heterojunction between materials having different crystal structures from which a good heterojunction is not originally obtained becomes possible,
One of the limitations in designing a semiconductor device using a heterojunction
One can be removed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are zinc-blende-type and wurtzite-type crystal structures, respectively. FIG. 3 is an atomic arrangement diagram on the (100) plane of the zinc-blende-type structure crystal. FIG. 5 is a diagram showing the relationship between the position of the second nearest atom in the zinc-blende and wurtzite structure, FIG. 5 is a cross-sectional view of the heterostructure in the embodiment, and FIG. FIG. 51 ... (100) GaAs substrate, 52 ... GaAs buffer layer, 53 ...
... Cd _0.58 Zn _0.42 S epitaxial layer, 61 ... GaAs substrate,
62: GaAs buffer layer, 63: Cd _0.58 Zn _0.42 S cladding layer, 64: GaAs active layer.

Claims (1)

(57) [Claims] CdZnS mixed crystal semiconductor, CdSeS, which originally has a wurtzite crystal structure on a zinc-blende-type semiconductor substrate
Or a crystal growth method for epitaxially growing a semiconductor material made of InGaN as a crystal having a zinc blende structure, wherein an anion atom and a cation atom constituting the semiconductor material are alternately supplied to a crystal growth interface of the semiconductor material over time. And growing a layer comprising said anion atom and said cation atom for each atomic layer. 2. 2. The crystal growth method according to claim 1, wherein the crystal having a zinc blende structure made of the semiconductor material is grown on a (100) plane of the semiconductor substrate. 3. 3. The crystal growth method according to claim 1, wherein the semiconductor substrate is GaAs.