JPH01125818A - Heterointerface formation - Google Patents

Abstract

PURPOSE:To make it possible to form a heterointerface of high quality by a method wherein the surface of a N-component mixed crystal of first semiconductor is flattened so that the stepping on the surface becomes a single molecular layer, the mixed crystal is grown one molecular layer only, and a M- component mixed crystal second semiconductor is epitaxially grown. CONSTITUTION:A N-component mixed crystal of first semiconductor is epitaxially grown, the surface of the first semiconductor is flattened so that it has the stepping of single molecular layer. Then, a Q-component crystal of third semiconductor, consisting of positive ionized element and a negative ionized element which are common to a N-component mixed crystal of first semiconductor and a M-component crystal or mixed crystal of second semiconductor (Q indicates the natural number of 2<=Q<=N) is grown in one-molecular layer only. The second semiconductor M-initial crystal is epitaxially grown. As a result, an interface is formed by a flat island in the height of one- molecular layer, and the undesirable mixed crystal layer of extremely steep, scattered carrier and disordering energy potential are not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a heterointerface, and particularly to a method for forming a high quality heterointerface of a compound semiconductor by molecular beam epitaxy.

[Prior Art] Most compound semiconductor devices such as two-dimensional electron gas transistors and quantum well lasers utilize betero junctions in which different types of semiconductor crystals are joined. The properties of the heterojunction interface (hereinafter referred to as heterointerface) affect carrier scattering, light emission, absorption, etc., and greatly influence device characteristics.

Therefore, it is important to form a high-quality interface that is flat, steep, and free of impurities and defects. Molecular beam epitaxy (Mo.
Regular Beam Epitaxy, hereinafter MB
(referred to as E) is widely practiced.

FIG. 2 shows a schematic cross-sectional view of an MBE apparatus commonly used to perform this MBE method. Molecular beam sources 20, 21, which heat a raw material containing elements constituting a desired crystal and eject each element in the form of molecular beams;
22.23 and a substrate holder 3 that heats and holds the substrate 4 in a temperature controllable manner independently of the molecular beam sources 20, 21, 22.23. Epitaxial growth is performed by ejecting molecular beams of raw material elements toward the substrate 4. In the MBE method, individual molecular beams are interrupted by opening and closing shutters 5a to 5d disposed in front of each molecular beam source, and the molecular beam intensity is modulated and controlled by setting the temperature of the evaporation source of each raw material. Can be done.

Conventionally, in the MBE method, each molecular beam source 20
A method of increasing the flatness of the interface by closing the shutters 58 to 5d of ~23 to interrupt the growth at the interface and waiting for several tens of seconds to several minutes has been reported for the GaAs/#GaAS hetero system (Japanese).・Journal of Applied Physics (Jpn, J, Ap
pl, Phys, ), 24. (1985).

(page 417). Here we will use this method,
It is called the E method.

FIG. 3 is an explanatory view schematically explaining a method for forming a Peter interface using the conventional interfacial BIMBE method in the order of steps. Here, A, B1. A case in which D ternary mixed crystals are laminated by the interface standby MBE method will be described.

In addition, A, B, and C represent a cationic element, and D represents an anionic element. Further, in the figure, element D is omitted.

In Figure 2, molecular beam sources 20, 21, 22 and 23
Put the raw materials of each element A, C, B and D into the
Shutter 5a in front of molecular beam sources 20.21 and 23.

5b and 5d are opened to grow the underlying AxCl-xD, the shutters 5a and 5b in front of the molecular beam sources 20 and 21 for the A and C elements are closed to irradiate only the D element. At the moment of interruption, as shown in FIG. 3(a), there are irregularities on the surface with a height of two molecular layers. However, if we continue to wait for 90 to 180 seconds, the A and C atoms or molecules on the surface will diffuse across the surface.
It is captured by steps and kinks on the surface, forming flat islands with a height of one molecular layer, as shown in FIG. 3(b). next,
The shutters 5a and 5C in front of the molecular beam sources 20 and 22 for elements A and B are opened, and A, B1 . By growing the D ternary mixed crystal, a desired heterointerface can be obtained as shown in FIG. 3(C).

The width of the transition region of the interface thus obtained is one molecular layer, and is extremely steep and flat.

[Problems to be Solved by the Invention] However, when the transition region for one molecular layer is examined in detail, this part is composed of A, B, and 03 as cationic elements.
It is a quaternary mixed crystal in which different types of elements coexist. This brings about the following disadvantages. That is, the quaternary mixed crystal scatters carriers more easily than the ternary mixed crystal. Additionally, undesirable energy potential disturbances occur at the interface, which impedes carrier transport in the direction along the interface. This problem is particularly serious because the quaternary mixed crystal composition of the transition region is not uniform in the plane parallel to the interface. Disturbances in the potential created at the interface act to widen the spectral width of exciton emission from a hanger well with such an interface. Therefore, this is a big problem when applying quantum wells to optical devices.

An object of the present invention was to solve the conventional problems as described above, and to provide a method for forming a high-quality heterointerface by preventing the formation of undesirable mixed crystals at the interface. There is a particular thing.

[Means for solving the problems] The present invention has the following features: 1. a second semiconductor containing at least one cationic element and one anionic element common to the first semiconductor N-element mixed crystal on a semiconductor N-element mixed crystal (N represents a natural number of 3 or more); In a method for forming a semiconductor hetero-interface formed by laminating M-element mixed crystals (M represents a natural number of 3 or more), a first growth step of epitaxially growing a first semiconductor N-element mixed crystal; a surface flattening step of flattening the surface of the semiconductor N-element mixed crystal so that the step becomes one molecular layer;
A third semiconductor composed of a cationic element and an anionic element common to the first N-element semiconductor mixed crystal and the second semiconductor M-element mixed crystal.
a second growth step of growing only one molecular layer of a semiconductor zero-element crystal or mixed crystal (Q represents a natural number of 2≦Q≦N);
A method for forming a heterointerface, comprising a third growth step of epitaxially growing the second semiconductor M-element mixed crystal.

[Operation] FIG. 1 is an explanatory diagram schematically explaining the method for forming a heterointerface according to the present invention in the order of steps. Here, AxCl-xD
A case will be described in which A, B1-VD ternary mixed crystals are laminated on a ternary mixed crystal. In addition, A, B, and C represent a cationic element, and D represents an anionic element. Further, in the figure, element D is omitted.

FIG. 1(a) shows the surface of the underlying semiconductor ternary mixed crystal when the growth of the underlying AxCl-xD was interrupted. Next, flattening is performed, as shown in Fig. 1(b).
After forming the surface state as shown in Figure 1(C), if a single molecular layer of crystal consisting of the element common to the first and second semiconductor mixed crystals is grown, it will become as shown in Figure 1(C), and a transition region at the interface will be formed. In this case, only a mixed crystal of at most N elements is formed. Next, Figure 1 (d
), the second semiconductor mixed crystals A, B1. D
are stacked to form a heterostructure. According to this method,
Unlike conventional methods, a mixed crystal having a higher order than the underlying mixed crystal, that is, a mixed crystal that easily scatters carriers, is not formed, and an interface with high carrier transport efficiency can be obtained.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

As the MBE apparatus used in the method of the present invention, for example, an apparatus as shown in FIG. 2 described above can be used. Hereinafter, as an example, in the explanatory diagram of FIG. 1, A is In, 3 is Ga, C@All, and D is AS, and InP (001
) As the first semiconductor N-element mixed crystal on the substrate, In, M,
A case will be described in which a heterostructure is formed by stacking In, Ga1-, and AS (V=0.53) using -xAs (x=0.52) as a second M-element conductor mixed crystal.

Each molecular beam source of the MBE apparatus shown in FIG.
In is filled in 21, Ga is filled in 22, M is filled in 22, and As is filled in 23 as raw materials.

First, the InP (001) substrate 4 was organically cleaned using a conventional method, and then chemically etched and cleaned.
Inside growth chamber 1, which is evacuated to an ultra-high vacuum on a Torr stand.

Attach it to the board holder 3 of.

Prior to the start of growth, each molecular beam source 2 of In, Ga, and
0°21.22 is the desired composition, ie InxAJ! 1-x
As (x=0.52> and In, Ga1-vAS (
The temperature is controlled so that V=0.53) is obtained. Further, the As molecular beam source 23 also has 2
The temperature is controlled so that an intensity of The temperature of the heater is raised and the surface of the InP substrate 4 is thermally cleaned under As pressure.
At 0°C, the oxide film and dirt on the surface are removed and the surface becomes clean. Next, the substrate temperature is stabilized at 550°C, the shutters 5a and 5c in front of the In and M molecular beam sources 20.22 are opened, and In0.52M0.48AS is grown by 0.5 pm (first growth step). . typical growth.

The speed was 0.81 Jfn/h.

Next, the shutter 5a of the In and N molecular beam source 20.22.

Closing 5C interrupts growth. Here, the moment of interruption of growth corresponds to the above-mentioned FIG. 1(a).

Next, flattening is performed by waiting for 120 seconds while irradiating AS (flattening step). This state corresponds to the above-mentioned FIG. 1(b).

Next, the shutter 5a in front of the In molecular beam source 20 is opened for 2.5 seconds corresponding to the thickness of one molecular layer, that is, about 2.93 people. This second growth step covers the surface with InAs (corresponding to FIG. 1(C)).

Subsequently, the shutter 5b in front of the Ga molecular beam source 21 is opened, In(,53Ga0.47AS) is grown, and a third growth step is performed.

Through the above steps, a hetero interface corresponding to that shown in FIG. 1(d) is formed. At this hetero interface, there is no quaternary mixed crystal in the direction parallel to the interface, and the interface is a ternary mixed crystal of In
There is a sharp switch from x, #1-x, As to Iny, Ga1-y, AS. Therefore, an interfacial transition region consisting of a quaternary mixed crystal, which is inevitable in the conventional interfacial BIMBE method, does not occur, and a high-quality interface can be obtained. In formed at the interface,
・M 1-, tAs and Iny・Ga1-y-As are,
Although it is not necessarily lattice matched to the InP substrate 4, since there is only one molecular layer, its influence can be almost ignored.

[Effects of the Invention] As described above, according to the method for forming a heterointerface of the present invention, the interface is formed from a flat island with a height of one molecular layer, and is not only extremely steep but also scatters carriers. or create undesirable mixed crystal layers that disturb the energy potential. As a result, it is suitable for fabricating electronic devices that utilize carrier transport phenomena along the Peter interface, and for fabricating optical devices using quantum wells in which mixed crystal (alloy) scattering at the interface affects the emission spectrum width.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a process diagram schematically explaining the method for forming a heterointerface of the present invention, FIG. 2 is a schematic cross-sectional view showing an example of an MBE apparatus used in the method of the present invention, and FIG. The figure shows the conventional interface IM
FIG. 3 is a process diagram schematically explaining a method for forming a Peter interface using the BE method. 1... Growth chamber 3... Substrate holder 4...
Substrate 5a to 5d...Shutter 9...Vacuum pump 20 to 23...Molecular beam sources A, B, C.
...Cationic element D...Anionic element

Claims (1)

[Claims] (1) At least one cationic element and one anionic element common to the first semiconductor N-element mixed crystal (N represents a natural number of 3 or more) on the first semiconductor N-element mixed crystal In the method for forming a semiconductor hetero-interface formed by stacking a second semiconductor M-element mixed crystal (M represents a natural number of 3 or more) including a first semiconductor M-element mixed crystal, a first growth step of epitaxially growing a first semiconductor N-element mixed crystal; A surface flattening step of flattening the surface of the grown first semiconductor N-element mixed crystal so that it becomes one molecular layer, and common to the first semiconductor N-element mixed crystal and the second semiconductor M-element mixed crystal. a second growth step of growing one molecular layer of a third semiconductor Q element crystal or mixed crystal (Q represents a natural number of 2≦Q≦N) consisting of a cationic element and an anionic element; and a third growth step of epitaxially growing a second semiconductor M-element mixed crystal.