JPH023536B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molecular beam generator that efficiently generates molecular beams of As ₂ , Sb ₂ , P ₂ and the like.

[Background of the invention]

In conventional molecular beam epitaxy equipment, e.g.
As shown in Fig. 1, a cell for generating a molecular beam of As is constructed by wrapping a heater wire 2 around the outer periphery of the cell 1 and installing a reflector 3 on the outside thereof to heat the metallic arsenic inside the cell 1. ₄ was occurring. However, when comparing a film grown with As _4- molecular beams and a film grown with As _2- molecular beams, the deep-level impurity concentration formed in the GaAs film is lower in the grown film with As _2- molecular beams. A good quality film can be obtained, and
It is possible to grow a film at a lower As pressure using an As _bimolecular beam, and by suppressing arsenic consumption, it improves arsenic contamination in molecular beam epitaxy equipment.
Molecular beam generators that generate As ₂ have recently been used because they can improve the productivity of grown crystals. As shown in Fig. 2, the conventional As ₂ molecular beam generator has a cell 4 that holds the raw material at the lower inner side, a heating heater 5 on the outer lower side, and a Kratzka partial heater 6 on the outer upper side. 5 and 6 are covered by reflectors 7 and 8, respectively. A cracker plate 9 is provided above the interior of the cell 4, and a heat shield plate 10 is provided between the cracker plate 9 and the lower raw material holding section 4' to ensure a temperature difference between the upper and lower parts of the cell 4. are doing. Metal arsenic held inside the lower part of cell 4 is heated to about 300°C by heat radiation from heater 5 located below the outside of cell 4.
Generates As ₄ molecular beam. The cracker plate 9 in the upper part of the cell 4 is heated to a higher temperature than the lower part of the cell 4 by the heat radiation of the cracker partial heater 6. In this state, the As ₄ molecular beam generated from the lower part of the cell 4 collides with the high-temperature Kratzka plate 9, causing thermal decomposition of As ₄ →2As ₂ to obtain an As ₂ molecular beam. However, in the above molecular beam generator, in order to raise the temperature of the Kratzka plate 9 to a temperature at which the As ₄ →2As ₂ reaction occurs with high efficiency, the temperature of the Kratzker partial heater 6 must be raised considerably. In this case, it becomes difficult to ensure a temperature difference between the upper part of the cell and the lower part of the cell with the heat shield plate 10, and the controllability of the temperature in the lower part of the cell deteriorates. Therefore, the temperature of the Kratzka partial heater 6 is suppressed to a relatively low temperature, resulting in high efficiency As ₄ →
_2As2 reaction is difficult to obtain.

[Purpose of the invention]

An object of the present invention is to obtain a molecular beam generator capable of efficiently generating a molecular beam of diatomic molecules.

[Summary of the invention]

In order to achieve the above object, a molecular beam generator for molecular beam epitaxy that generates a molecular beam of diatomic molecules according to the present invention includes a cell that holds a raw material in the lower part of the inside and has a reflector for heat insulation on the outside; A heater is wound along the lower outer periphery of the cell between the reflector and a heat shielding plate provided above the raw material holding part in the cell, and the reflector is above the heat shielding plate covered with the reflector. By installing a Kratzka heater in the cell covered by the cell, a molecular beam of 4-atom molecules generated in the lower part of the cell is made to enter the Kratzka heater in a straight line to obtain a molecular beam of diatomic molecules. It is.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing an embodiment of a molecular beam generating device for generating a molecular beam of diatomic molecules according to the present invention. In Figure 3, this molecular beam generator is
A cell 4 which holds a raw material at the inner lower part and has a heat insulating reflector 78 at the outer side, and a heater 5 wound between the reflector 7 along the outer periphery of the lower part of the cell 4,
A cracker heater 11 is provided above the heat shield plate 10 in the cell 4 covered by the reflector 8. Cell 4 in the above device
Heater 5 holds metal arsenic as a raw material in the lower part of the inner part.
is heated to raise the temperature of the inner lower part of the cell ₄ to about 300°C, at which point a four-molecule beam of As is generated from metal arsenic. Heater 11 for cracker on top of cell 4
When heated to about 900°C, the As ₄ beam generated at the bottom of cell 4 is transferred to cracker heater 1 at the top of cell 4.
1 and is thermally decomposed by the heat of the cracker heater 11 to generate an As ₂ molecular beam. In this embodiment, as mentioned above, the As ₄ molecular beam is directly incident on the cracker beam 11 to cause the As ₄ →2As ₂ reaction, so the temperature of the cracker heater 11 is the same as that of the conventional device shown in FIG. The temperature may be lower than that of the Kratzka partial heater 6, and less input power is required. Furthermore, in the past, the influence of the temperature of the Kratzka partial heater 6 on the raw material holding portion 4' in the cell 4 was large, so in this embodiment, the heat radiation from the upper part to the lower part in the cell 4 is reduced, and the heat shielding plate 10
As a result of this intervention, it is possible to make the upper part of the cell 4 higher in temperature than before, so that an _As bimolecular beam can be generated efficiently. The shape of the cracker heater 11 may be a single coil, a double coil, a mortar shape, or wound around a quartz tube, but is not limited to these shapes. In the conventional indirect heating type molecular beam generator in which the Kratzka plate 9 shown in FIG. 2 is heated by the Kratzker partial heater 6, the As pressure is controlled to about 1×10 ^-6 ton, which is optimal for forming a high-quality film. The current that can be passed through the Kratzka partial heater 6 when attempting to do so is 3A.
Although to a certain extent, the above-mentioned Kratzka partial heater 6
Even if a current of 3A or more is applied to the
It is difficult to raise the temperature to around 900℃, which makes it difficult for the As ₄ →2As ₂ reaction to occur. Furthermore, when the input power of the Kratzka partial heater 6 is increased, the metal arsenic in the lower part of the cell 4 is heated by heat radiation, resulting in the generation of many _As4 molecular beams, resulting in high efficiency.
It becomes difficult to obtain an As _bimolecular beam. In contrast, the molecular beam generator according to the present invention generates a beam by passing a current of about 2.5A through the cracker heater 11.
The temperature of the Kratzka heater 11 can sufficiently reach the temperature of about 900°C at which the As ₄ →2As ₂ reaction takes place efficiently, and the heat radiation from the Kratzka heater 11 to the lower part of the cell 4 is different from that of the conventional device. The As pressure can be sufficiently controlled to about 1×10 ⁻⁶ ton. In the above embodiment, As ₄ is thermally decomposed in the cell 4 to generate an As ₂ molecular beam, but the molecular beam generator of the present invention can be used to generate Sb ₄ , P ₄
Molecular beams of diatomic molecules such as Sb ₂ and P ₂ can be generated in the same manner as described above by thermally decomposing other tetraatomic molecules such as Sb 2 and P 2 .

〔Effect of the invention〕

As described above, the molecular beam generator for molecular beam epitaxy that generates a molecular beam of diatomic molecules according to the present invention comprises a cell that holds a raw material at the inner lower part and has a heat insulating reflector on the outer side, and a lower outer periphery of the cell. and a heat shield plate provided above the raw material holding part in the cell, and a heater for crackers is provided above the heat shield plate in the cell covered by the reflector. By establishing
A molecular beam of four atoms generated in the lower part of the cell is directly incident on the cracker heater and thermally decomposed.
Because we made it possible to generate molecular beams of atoms and molecules,
Thermal shielding between the high-temperature part at the top and the low-temperature part at the bottom of the cell becomes easy, and the temperature of the cracker heater at the top can be raised sufficiently, making it possible to efficiently generate a molecular beam of diatomic molecules. . In addition, the consumption of raw materials is reduced due to highly efficient molecular beam generation of diatomic molecules, and it is possible to form a high-quality film.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional molecular beam generator, Figure 2
The figure is a block diagram of a conventional molecular beam generator that generates a molecular beam of diatomic molecules, and FIG. 3 is a block diagram of a molecular beam generator of the present invention that generates a molecular beam of diatomic molecules. 4... Cell, 4'... Raw material holding section, 5... Heater, 7, 8... Reflector, 10... Heat shielding plate,
11... Heater for Klatzka.

Claims (1)

[Claims] 1 The atomic molecules of group elements such as As ₄ , Sb ₄ , and P ₄ as raw materials are thermally decomposed to produce 2 atoms such as As ₂ , Sb ₂ , and P ₂ .
In a molecular beam generator for molecular beam epitaxy that generates molecular beams of atoms and molecules, there is a cell between a cell that holds a raw material at the bottom inside and a reflector for heat insulation outside, and a reflector along the outer periphery of the bottom of the cell. The invention is characterized by comprising a wound heater and a heat shielding plate provided above the raw material holding portion in the cell, and a cracker heater provided in the cell covered by the reflector above the heat shielding plate. Molecular beam generator.