JPS62119194A - Molecular beam source - Google Patents

Abstract

PURPOSE:To obtain the titled molecular beam source wherein the flow of heat into a crucible is reduced and capable of easily controlling the intensity of a group-V molecular beam by using PBN at the high temp. part for decomposing a group-V tetratomic molecule, namely the raw material of a III-V compd. semiconductor, into a diatomic molecule, and inserting a perforated PBN sheet. CONSTITUTION:The crucible 1, a cracker part 2 which is the high-temp. part for cracking, and a connecting part 3 for connecting the crucible and the cracker part are formed with a high-purity PBN material which is not decomposed even at high temp. The perforated sheet 4, for example, is inserted between the crucible 1 and the cracker part 2 and between the crucible 1 and the connecting part 3 so that the c axis is paralleled with the heat flow. Then the crucible 1 charged with As 8 and the cracker part 2 are heated with respectively independent heaters 5 and 6. The temp. of the crucible 1 (as well as the cracker part 2) is monitored by a thermocouple 7. At this time, since heat conduction is controlled by the sheet 4, a stable molecular beam with less impurities can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a molecular beam source that simultaneously improves the purity of a molecular beam that generates group (III) diatomic molecules and improves the controllability of the molecular beam intensity. .

[Conventional technology]

Conventionally, when growing ■-V group compound semiconductors such as G, A, etc. by the molecular beam crystal growth method, metal G and hard wood A,
They were placed in separate crucibles and heated in vacuum to form molecular beams, which were then supplied to the substrate crystal to form a growth layer on top of it. At this time A.

is supplied as a four-atomic molecule, but it has been reported that the quality of the crystal should improve if it is thermally decomposed into diatomic molecules.

For example, Mr. Kintzell of the Max Blank Institute et al.
Applied Physics in 982
In a paper published in Volume A28, pages 167-173 of Physics), they reported that deep levels were reduced by changing from a tetraatomic molecule to a diatomic molecule. Neave et al. of the Phillips Institute published a similar report in Applied Physics Letters in 1980.
31 of Volume 36 of Physics Letters)
It's one page. However, G and A have grown up.

The impurity concentration is 3 x 1016 cm-3 or more, which has the disadvantage that high-purity crystals cannot be obtained.

[Problem that the invention seeks to solve]

Although there is a deep level, the carrier concentration is 1014C11
The reason why the purity of the crystal was inferior to that obtained using tetraatomic molecules, which yielded three crystals, is said to be due to the material used in the part that thermally decomposes the tetraatomic molecules into diatomic molecules.

In other words, PBN (pyrolitic boro
n n1tride) is used as the crucible material, whereas in growth using diatomic molecules, metals such as quartz (S+0□) and T are used in the part that thermally decomposes. By reaction with group materials,
This is because impurities are taken into the growth layer.

The problem with the conventional technology lies in the selection of materials for the high-temperature parts.
It would be better to use high-purity PBN etc.
Another problem arises in this case.

When a PBN tube is used in the cracker part, the a-axis of the PBN is oriented in the normal direction of the tube due to the manufacturing method, and the in-plane direction of the tube is the a-axis. The thermal conductivity of PBN is small in the C-axis direction and large in the a-axis direction, and the value is 0.007 cal -5 at 800°C.
ec-'-am-'-℃-' and 0.15 c a l-
sec-'-cm-""C-1.

In order to give the PBN tube enough strength to support the cracker part, the wall thickness must be reduced to about 1 inch, but for this reason the amount of heat conducted from the cracker part to the crucible is 0.
It will be as big as a metal tube with a thickness of about 5 am. Therefore, the temperature of the crucible increases due to the flow of heat from the cracker portion into the crucible, making it impossible to control the intensity of the group V molecular beam. This is because the temperature required for the cracker part is about 1000°C, whereas the temperature required for the crucible is only 300°C.

The purpose of the present invention is to solve the above-mentioned problems and to produce high-purity PB.
The object of the present invention is to provide a new molecular beam source with a part of lacquer that uses N material, maintains its strength, and reduces the inflow of heat from the cracker part to the crucible, making it easy to control the intensity of group V molecular beams. .

[Means for solving problems]

The gist of this invention is that high-purity P is added to the cracker part, which is a high-temperature part, in order to prevent impurities from entering the growth layer.
In addition to solving the above problem using BN, etc., cut one or more places between the cracker part and the crucible of PBH with a thickness of about 11II+, and place a PBN plate in that part so that the a-axis is in the direction of heat flow. By inserting the PBN so as to be parallel to the C-axis direction, heat conduction is suppressed by utilizing the small thermal conductivity of PBN in the C-axis direction.

[Effect]

PBN is thermally stable and highly purified, so
Suitable for places that require high heat of around 1000°C, such as cracker parts. Taking advantage of the fact that the thermal conductivity of PBN in the C-axis direction is 1/20 of that in the a-axis direction, heat conduction can be greatly suppressed by placing it in the middle of the heat conduction direction so that the a-axis is parallel to the heat flow. can.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a conceptual diagram for explaining a first embodiment of the present invention. Crucible 1 made of PBN and cracker part 2. A PBN plate with holes was sandwiched between the crucible and the connecting portion 3. The cracker part and crucible each have independent heaters 5.
, 6, and the temperature of the crucible was monitored with a thermocouple 7.

The cracker section was also monitored with a thermocouple, but not shown. 100 grams of solid arsenic 8 was placed in a crucible. When the cracker part was heated to 800℃, the temperature reached approximately 200℃ without power being supplied to the crucible heater, and by supplying a small amount of power to the crucible heater, the temperature of the crucible was raised to approximately 3℃.
By setting the temperature to 00°C, it was possible to stably supply an arsenic molecular beam containing 80% diatomic molecules with a molecular beam intensity of 1X10-'Torr. At the same time, a molecular beam of 01 was supplied to grow 3 μm at a growth rate of 1 μm/h, and hole measurements were performed. The carrier concentration was approximately lXl0"Ω"3
The growth layer showed an n-type structure, and a grown layer with purity about one order of magnitude higher than that of the conventional method was obtained.

(Second Embodiment) Fig. 2 is a conceptual diagram for explaining the second embodiment of the present invention. A board was inserted. In FIG. 2, parts with the same numbers as in FIG. 1 have the same names and perform the same functions. Since heat conduction could be suppressed to a greater degree than in the first example, the temperature of the cracker section could be raised to 1000°C.

For this reason, an arsenic molecular beam containing more than 90% of diatomic molecules is
It was possible to stably supply the molecular beam with a molecular beam intensity of Xl0-'Torr. The carrier concentration of the G, A, and growth layers thus obtained was 1-2×10"cm-', and a high-purity growth layer was obtained.

〔Effect of the invention〕

As explained above, the molecular beam source obtained by the present invention can obtain a molecular beam that is more stable and has fewer impurities than the conventional molecular beam source for making group V diatomic molecules, and can produce high-quality crystals. can grow.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram for explaining a first embodiment of the present invention, and FIG. 2 is a conceptual diagram for explaining a second embodiment of the present invention. 1... Crucible, 2... Cracker part, 3... Connecting part, 4... PBN board with holes, 5, 6... Heater, 7... Thermocouple, 8... Arsenic . $ 7 dent $ 2 7! I

Claims (2)

[Claims] (1) A crucible filled with a group V molecular beam material for a III-V compound semiconductor to be grown on a substrate, and a group V four-atom molecule generated by heating the crucible to an even higher temperature. It consists of a cracker part that decomposes into diatomic molecules, and a connecting part that connects the crucible and the cracker part. A PBN plate with holes is sandwiched between them, and C of the above PBN plate is inserted.
A molecular beam source whose axis is parallel to the direction of heat flow. (2) The connecting part is further divided into a plurality of parts, and a PBN plate having holes is sandwiched between each part, and the C axis of the PBN plate is parallel to the heat flow direction. Molecular beam source described in ).