JPS63122211A - Molecular beam generating device - Google Patents

Abstract

PURPOSE:To grow a crystal having the microscopic structure of a superlattice and the like into an excellent controllability by a method wherein a shutter is formed in a conical shape, and the title device is constructed in such a manner that the vertex of the device is arranged in the direction of a crucible. CONSTITUTION:A shutter 4a is formed into a conical shape, and it is arranged in such a manner this its vertex is directed toward a crucible. A part of the heat radiation emitted from the crucible and the surface of a molecular beam material comes out to outside the crucible without interruption by the shutter 4a. Also, a part of the heat radiation made incident on the shutter is reflected in the angle equal to the angle of incidence, but as the shutter 4a is formed into a conical shape having the vertical angle of 90 deg., all the heat radiation is reflected in the direction outside the crucible 1. Accordingly, the rate of the heat radiation reflected by the shutter 4a and returned to the crucible can be made smaller than that of the previous examples, and the difference in the surface temperature of a molecular beam material 3 when the shutter 4a is closed and when it is opened can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molecular beam generating device for a molecular beam epitaxial device, and particularly to a molecular beam generating device whose molecular beam intensity is stable when the shutter is opened and closed.

[Prior art] Molecular beam epitaxial method involves a method in which molecular beams generated by heating a source molecular beam material in an ultra-high vacuum are incident on a heated substrate to grow crystals. . Since the material is supplied in the form of a molecular beam, the bimolecular beam epitaxial method has advantages such as good controllability of film thickness and impurity doping, and the ability to obtain a steep heterojunction.

As shown in Fig. 3, the conventional molecular beam generator uses a heater 2 placed around a crucible 1 to heat the molecular beam material 3 placed in the crucible, evaporate or sublimate it, and release the molecular beam into the crucible opening. Make it squirt from the part.

The molecular beam is interrupted by mechanically opening and closing a shutter 4bvi placed close to the crucible opening.

In FIG. 3, numeral 5 is a heat reflecting plate, 6FX is a thermocouple connected to a temperature-sensitive wire, and 7 is a liquid N reservoir for cooling.

[Problem that the invention seeks to solve]

The above-mentioned molecular beam generator uses GaAs (gallium arsenide).
When performing crystal growth, the temperature of the crucible containing Ga (gallium) is controlled to t-1000 to 1200°C in order to obtain a molecular beam intensity that provides a growth rate of about 1 μm/h.

Molecule by opening shutter 4b? When fM is ejected, heat is dissipated from the surface of the molecular beam material 3 by thermal radiation, so the surface temperature of the molecular beam material 3 becomes lower than the internal temperature. On the other hand, when the shutter is closed to block the molecular beam, the surface temperature of the 9-molecular beam material 3 is lower than when the shutter 4b is open because the radiant heat is reflected by the shutter 4b and returns to the crucible. It gets expensive. Therefore,
Immediately after opening the shutter 4b, the surface temperature of the molecular beam material 3 changes over time, so the nine molecular beam intensity shows a value different from the steady value.

FIG. 4 shows the results of measuring changes in molecular beam intensity over time when Ga (gallium) was placed in a PBN (pyrolytic boron nitride) crucible and heated to 1100° C. in a vacuum. The single molecule beam intensity was measured using a Bayard-Alpert type ionization vacuum gauge. 9 after opening the shutter
The bimolecular beam intensity is about 20% higher than when it stabilizes after a sufficient period of time has elapsed. The time required for the molecular beam intensity to reach a steady value from the time the shutter is opened varies depending on the temperature of the crucible, the shape of the molecular beam material, the time the shutter is closed, etc., but is from several tens of seconds to several minutes.

The growth time of the crystal layer with a thickness of several tens of amps to several hundred is acceptable.

During periods when the molecular beam intensity is unstable, it becomes difficult to control film thickness, impurity doping, mixed crystal ratio, etc., and crystal explosions in ultra-thin film structures such as superlattices and lattice matching in heterojunctions become difficult. There were drawbacks.

[Means for solving problems]

The molecular beam generator of the present invention has a structure in which the shutter has a solar eclipse shape and is disposed with its apex facing toward the crucible.

〔Example〕

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

FIG. 1 is a sectional view of one embodiment of the present invention. In the figures, the same numbers as in FIG. 3 are the same components as in FIG. 3. The shutter 4a is different from conventional ones in that the shape of the shutter is solar eclipse-like, and its apex is oriented toward the crucible. In this practical example,
The shutter 4a has a solar eclipse shape with an apex angle of 90°. Here, even if the shutter 4a2 is closed.

Although there is a gap between the crucible and the shutter 4a, if the outer diameter of the shutter 48 is made sufficiently large, the shielding effect of the molecular beam will not be impaired. It goes out of Crucible 1 without being blocked. Also, a part of the good thermal radiation incident on the shutter is reflected at an angle equal to the incident angle, but the shutter 4
Since a has a solar eclipse shape with an apex angle of 90'', all one reflection direction is outside the crucible l. Therefore, the proportion of thermal radiation that is reflected by the shutter 4a and returns into the crucible is:

The third factor can be made smaller compared to the conventional example.

The difference in surface temperature of the molecular beam material 3 when the shutter 4a is closed and when it is opened can be alleviated. Figure 4 shows Ga in a PBN crucible in vacuum at 1100°C.
These are the results of measuring changes in molecular beam intensity over time when heated to ℃. Immediately after the shutter was opened, the fluctuation of the molecular beam intensity was within 1 inch. [Effects of the Invention] As explained above, the present invention suppresses the temperature increase on the surface of the molecular beam material due to the reflection of thermal radiation at the shutter. By suppressing this, it is possible to reduce fluctuations in the molecular beam intensity immediately after the shutter is opened, and there is an effect that crystals having a fine structure such as a superlattice can be grown with good controllability.

[Brief explanation of the drawing]

11th is a sectional view of the molecular beam generator of the present invention. FIG. 2 shows the change over time in the Ga molecular beam intensity immediately after the shutter is opened when using the molecular beam generator of the present invention. FIG. 3 is a cross-sectional view of a conventional molecular beam generator. FIG. 4 shows the change over time in the Ga molecular beam intensity immediately after the shutter is opened when using a conventional molecular beam generator. DESCRIPTION OF SYMBOLS 1... Crucible, 2... Heater, 3... Molecular beam material, 4a, 4b... Shutter, 5... Heat reflection plate, 6... Thermocouple, 7... Liquid nitrogen reservoir . Fang 1 figure yflJz 3rd figure confrontation r4 箭4 old

Claims (1)

[Claims] A molecular beam generation device in which a shutter is disposed at the opening of a crucible for supplying molecular beams to intermittent molecular beams is characterized in that the shape of the shutter is circular and the apex is directed toward the crucible. Molecular beam generator.