JPH0449629A - Compound semiconductor crystal and its manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a high-quality compound semiconductor crystal with less dislocation density by allowing the compound semiconductor crystal which is subjected to epitaxial growth on a substrate to be subjected to thermal cycle annealing at a line-shared heating region. CONSTITUTION:A CdTe crystal 31 is formed on a GaAs substrate 1 by the hot wall epitaxial growth method, the molecular beam epitaxial growth method, or the MOCVD method. This GaAs substrate 1 is introduced into a container 32 which is made of crystal glass, the Gaps substrate 1 is heated by a heater 33 which is provided around the container, approximately 1mm line-shared heating region 3 is formed using an Ar gas laser light source 34 and temperature of this heating region 3 is adjusted to 700 deg.C. Then, this line-shared heating region 3 is moved along a horizontal direction of a substrate using a scanning mirror and this scanning is performed for approximately 10 times.

Description

[Detailed Description of the Invention] [Summary] Regarding a compound semiconductor crystal and a method for manufacturing the compound semiconductor crystal, the compound semiconductor crystal formed by epitaxial growth on a substrate has a low dislocation density, and the method for manufacturing the crystal. It is composed of a compound semiconductor crystal epitaxially grown on a substrate and thermally cycle annealed in a linear heating region.

Further, it is constructed by thermally annealing the crystal by scanning a linear heating region on the crystal during epitaxial growth of the compound semiconductor crystal on the substrate, or after epitaxially growing the crystal on the substrate.

[Industrial application field]

The present invention relates to a compound semiconductor crystal and a method for manufacturing the same, and more particularly to a compound semiconductor crystal that can be formed on a substrate by epitaxial growth and has a low dislocation density, and a method for manufacturing the same.

Mercury, cadmium, tellurium (Hg, -, Cd) with narrow energy band gaps are used as materials for forming infrared sensing elements.
A compound semiconductor crystal such as xTe) is used.

Vapor phase,
Alternatively, a liquid phase epitaxial growth method is used.

In the production of such compound semiconductor crystals, cadmium-tellurium (CdTe) M plates have traditionally been used, but since this substrate is expensive, recently GaAs substrates have been used, and CdTe crystals, Hg+ -x CdxTe
Crystals are successively grown heteroepitaxially and stacked into multiple layers.

However, Hg+ grown heteroepitaxially in this way
Since the -11Cdx Te crystal has a high dislocation density, there is a need for a technique to keep this within a predetermined range.

[Conventional technology]

Conventionally, for example, gallium arsenide (G) was deposited on a silicon (Si) substrate.
aAs) When growing a crystal heteroepitaxially, S
By forming a strained superlattice layer in which aluminum arsenide (A/As) layers and GaAs layers are alternately laminated in multiple thin layers of several tens of layers on an i-substrate, and by laminating a GaAs crystal on top of this, There is a method of reducing the dislocation density of the GaAs crystal that is formed.

However, with this method, it is difficult and complicated to form the strained superlattice layer.

Furthermore, Japanese Patent Application Laid-Open No. 56-61179 discloses a method of heating a substrate with point defects due to the introduction of impurity atoms by ion implantation using a laser to restore the state to the state before the ion implantation.

However, this method only restores point defects in the very surface layer of the substrate to its original state, and it is difficult to reduce the dislocation density of the entire crystal of a given thickness formed on the substrate. Not enough.

There is also a conventional solid-phase epitaxial growth method in which polycrystalline Si is formed on a Si substrate by CVD and then laser annealed to form single-crystal Si, but this method requires heating the entire substrate. .

Also, Japanese Patent Application No. 61-226994, Japanese Patent Application No. 62-619
In No. 69, a crystal having a lattice constant different from that of the substrate was heteroepitaxially grown on a substrate, and the temperature of the entire substrate was increased or decreased to perform thermal cycle annealing to reduce the dislocation density of the crystal on the substrate. Although there are some examples, even in this case, the entire substrate is heated.

[Problem to be solved by the invention]

However, in thermal cycle annealing in which the temperature of the entire substrate is raised and lowered in this manner, if there is no difference in thermal expansion coefficient between the substrate and the epitaxial layer, no stress is applied to the heterointerface between the substrate and the epitaxial crystal. Therefore, there is no movement of positive or negative dislocations running in the lateral direction within the epitaxial layer, and therefore dislocation coalescence and annihilation do not occur, resulting in a problem that dislocations are not reduced.

In addition, the driving force for moving dislocations is given energy only from the heterointerface between the substrate and the epitaxial crystal, so methods that heat both the epitaxial crystal and the substrate have the problem that dislocations are difficult to move. There is also.

The object of the present invention is to solve the above-mentioned problems and provide a compound semiconductor crystal in which dislocations can be easily moved and dislocations can be easily eliminated by a simple method, and a method for producing the crystal.

[Means to solve the problem]

The compound semiconductor crystal of the present invention that achieves the above object has a first
As shown in the principle diagrams of FIG. 1(a) and FIG. 1(b), a compound semiconductor crystal 2 is epitaxially grown on a substrate 1.
is formed by thermal cycle annealing in the linear heating region 3.

The method for manufacturing the compound semiconductor crystal is shown in Figure 1(a).
As shown in the principle diagram of FIG.
Alternatively, after epitaxially growing the crystal 2 on the substrate 1, the crystal 2 is thermally annealed by scanning the linear heating region 3 over the crystal.

Further, the compound semiconductor crystal 2 may be a single crystal grown on the substrate 1, or a plurality of stacked heterocrystals having different compositions.

Further, the heating region 3 is formed by a light source that generates light of a wavelength that is selectively absorbed by a single compound semiconductor crystal on the substrate or a predetermined crystal of the plurality of compound semiconductor crystals. shall be taken as a thing.

Further, the heating region 3 is scanned over the compound semiconductor crystal from above the substrate 1 or from below the substrate alternately or simultaneously.

Further, in order to selectively form the heating region 3 in the compound semiconductor crystal 2, the heating region is scanned over the compound semiconductor crystal while turning on and off the light source for forming the heating region, and the high dislocation density region is formed in the compound semiconductor crystal. Another method is to selectively form low dislocation density regions and selectively form elements in the low dislocation density regions of the compound semiconductor crystal.

[For production]

As shown in the plan view of FIG. 1(a) and FIG. 1(b) of the cross-sectional view of FIG. 1(a), a compound semiconductor crystal 2 is formed on a substrate 1, and a width of about 1 ml 11 When the heating area 3 caused by heating by the laser light source is scanned along the directions of arrows A and B, the heating area changes at predetermined time intervals as shown by the peak values of IIA and IIB, as shown by the curve 11 in FIG. 3 passes periodically over the compound semiconductor crystal. A temperature gradient is generated in the compound semiconductor crystal 2 across the heating region 3. A difference in lattice constant occurs within the crystal due to thermal expansion based on the temperature difference due to this temperature gradient.

When the heating area is moved in this state, a fixed point 11 will be formed on the substrate.
At A, the temperature changes periodically from the substrate temperature T0 to the maximum temperature T of the heating region.

This occurs not only at the hetero interface between the substrate and the compound semiconductor crystal, but also at the epitaxially grown compound semiconductor crystal 2.
Figure 1 (al) and Figure 1 (b) occur throughout the
), the movement of dislocations in the positive direction shown in the direction of arrow A,
Dislocations move in the negative direction shown in the direction of arrow B, and the coalescence and annihilation of these dislocations moving in both positive and negative directions is promoted.

Further, as shown in FIG. 3, a compound semiconductor crystal 21 made of a light-absorbing piece of HgTe that absorbs light with a wavelength of 3 to 5 μm and a light-transmitting compound of CdTe that transmits light with a wavelength of 3 to 5 μm are disposed on the substrate 1. A semiconductor crystal 22 is grown heteroepitaxially, and a laser light source 34 irradiates the substrate with laser light having a wavelength that is absorbed only by the light-absorbing compound semiconductor crystal. Then, along with the temperature gradient formed when the heating region 3 is moved along the lateral direction of the substrate, a driving force for the movement of dislocations due to the mutual thermal expansion coefficient difference of the laminated epitaxial crystals is added. This makes it possible to further coalesce and eliminate dislocations.

Further, after forming a plurality of heteroepitaxial crystals of the above-mentioned light-absorbing compound semiconductor crystal and light-transmitting compound semiconductor crystal on the substrate, light sources provided on both sides of the front and back surfaces of the substrate can be used independently or By scanning in the same direction, heated regions are formed on the front and back sides of the epitaxial crystal layer, thereby further reducing dislocations.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 2, a CdTe crystal 3 is placed on a GaAs substrate 1.
1 is formed to a thickness of about 1 μm using a real wall epitaxial growth method, a molecular beam epitaxial growth method, or an MOCVD method.

This GaAs substrate 1 is introduced into a container 32 made of quartz glass, and then the GaAs substrate 1 is heated to 200° C. (To) with a heater 33 provided around the container, and heated to 111° C. using an Ar gas laser light source 34. A linear heating region 3 of about 100° C. is formed, and the temperature of this heating region 3 is adjusted to 700° C.

Next, this linear heating area 3 is scanned by a scanning mirror (not shown).
was used to move laterally across the substrate at a speed of 1 mm/min in the direction of arrow A or direction B, and this scanning was repeated for 10 minutes.
Repeat several times.

Here, Cd epitaxially grown on the GaAs substrate 1
In order to prevent Cd from evaporating from the Te crystal 31,
Although not shown, a source crystal of Cd is sealed in the container 32, and the container is filled with Cd vapor to create a Cd atmosphere inside the container 32.

By doing so, a CdTe crystal 31 with a dislocation density reduced to 106 was obtained on the GaAs substrate 1.

CdTe crystals formed by conventional methods without using such methods are 10? It has a dislocation density of approximately

Note that in this example, heat treatment was performed after epitaxial growth, but after forming epitaxial crystals to a predetermined thickness,
This heat treatment may be performed to further form epitaxial crystals.

Next, a second embodiment of the present invention is shown in FIG.

As shown in the figure, the hot wall epitaxial growth method, molecular beam epitaxial growth method,
A light-absorbing compound semiconductor crystal 21 made of HgTe is formed to a thickness of about 1 μm using the MOCVD method, and a compound semiconductor crystal 2 made of CdTe as a light-transmitting layer is formed thereon.
2 to a thickness of 1 μm.

Then, this substrate is enclosed in a transparent quartz container 32,
A laser beam having a wavelength of 2 to 3 μm is irradiated onto the substrate using a laser light source 34.

This laser light source is a light source that emits light of a wavelength that is absorbed by a compound semiconductor crystal 21 for light absorption and transmitted through a compound semiconductor crystal 22 for light transmission.

The light of this wavelength is transmitted through a compound semiconductor crystal 22 for light transmission.
The light is transmitted through the compound semiconductor crystal 21 and absorbed by the compound semiconductor crystal 21, and a heated region 3 with a width of about 1 mm is formed by the compound semiconductor crystal 2.
1, optical systems such as lenses and mirrors (not shown) and the emitted light of the laser light source are adjusted. Although this laser beam is not shown, a mirror or the like is used to
Scanning is performed about 10 times in the direction of arrow A or B at a speed of about /min.

Then, this heating region 3 forms a light-transmitting compound semiconductor crystal 2 which is grown heteroepitaxially with a substrate having a different lattice constant.
The compound semiconductor crystal 21 for light absorption
A temperature gradient also occurs at the vertical hetero interfaces 21A and 21B, making it easier for dislocations to move.

As another example, a CdTe crystal and a HgI-x Cdx Te crystal are stacked on a GaAs substrate, and the laser beam irradiation is turned on and off when scanning with the laser beam, and the Hg of the light absorption layer, -, Cdx A region heated by a laser beam or a region not heated is selectively formed inside the T6 crystal to selectively form a high dislocation density region and a low dislocation density region, and the low dislocation density region is When element-forming impurities are introduced to form an infrared sensing element, the high dislocation density region becomes an element bone MjJI region, and an array-shaped infrared sensing element in which elements are separated can be easily obtained.

Further, a light source may also be arranged on the back side of the substrate, and laser light may be irradiated from both the front and back sides of the substrate alternately or simultaneously, which will serve as the heating area.

〔Effect of the invention〕

As is clear from the above description, the present invention has the effect of easily obtaining a high quality compound semiconductor crystal with a low dislocation density.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1(a) and 1(b) are principle diagrams of the compound semiconductor crystal of the present invention and its manufacturing method, FIG. 2 is an explanatory diagram of the first embodiment of the present invention, FIG. 3 is an explanatory diagram of the second embodiment of the present invention, and FIG. 4 is a temperature distribution diagram at a fixed point of the crystal in the method of the present invention. In the figure, 1 is a substrate (GaAs substrate), 2 is a compound semiconductor crystal, and 3 is a substrate (GaAs substrate).
is the heating region, 11 is the heating temperature distribution curve, IIA, II
B is the peak value of the heating temperature distribution curve, 21 is a compound semiconductor crystal (HgTe), 21A and 21B are hetero interfaces, 22
31 is a CdTe crystal, 32 is a container, 33 is a heater, and 34 is a laser light source.

Claims (6)

[Claims] (1) A compound semiconductor crystal (2) epitaxially grown on a substrate (1) is formed into a scannable linear heating area (3)
1. A compound semiconductor crystal characterized by being thermally cycle annealed. (2) During the epitaxial growth of the compound semiconductor crystal (2) on the substrate (1), or after the epitaxial growth, a linear heating region (
3) A method for manufacturing a compound semiconductor crystal, which comprises scanning the crystal and subjecting the crystal to thermal cycle annealing. (3) The compound semiconductor crystal (2) grown on the substrate (1) is a single crystal (31) or a stack of multiple compound semiconductor crystals (21, 22) having different compositions. The method for producing a compound semiconductor crystal according to claim (2). (4) The heating region (3) is a single crystal (31) on the substrate.
) or a light source (34) having a wavelength that is selectively absorbed by a predetermined crystal (21) of the plurality of compound semiconductor crystals (21, 22). The method for producing a compound semiconductor crystal according to (2) or (3). (5) Claim (2), (3) or (4) characterized in that the heating region (3) is scanned over the compound semiconductor crystal (2) alternately or simultaneously from above the substrate or from below the substrate.
A method for manufacturing the compound semiconductor crystal described above. (6) Scanning the heating region forming light source while turning on and off so that the heating region (3) is selectively formed in the compound semiconductor crystal (2), and forming a high dislocation density region or a low dislocation density region in the compound semiconductor crystal. According to claim (2), (3), (4) or (5), wherein dislocation density regions are selectively formed and elements are selectively formed in low dislocation density regions of the compound semiconductor crystal. A method for manufacturing the compound semiconductor crystal described above.