JPS5841655B2 - The best way to get started - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molecular beam crystal growth method that includes an etching component.

A new molecular beam epitaxial growth method has been developed that provides better control than conventional epitaxial growth methods such as vapor phase epitaxy and liquid phase epitaxy.

The molecular beam method has the following advantages: ultra-thin crystals on the order of IOA, multi-component crystal films, multilayered structures and periodicity, and atomically flat surfaces. It has many advantages, such as the ability to obtain crystals and the ability to obtain crystalline films at low temperatures, and is expected to find many practical applications.

However, while having these advantages, the molecular beam growth method has essential drawbacks such as poor crystallinity, low hole mobility, and impurity concentration cannot be lowered due to residual gas. In terms of crystallinity, when compared with conventional techniques such as vapor phase growth method and liquid phase growth method, there is a disadvantage that the quality is much lower.

Therefore, how to produce materials with good crystallinity is an important issue in molecular beam growth methods.

The present invention provides a new method that eliminates the drawbacks of the conventional molecular beam crystal growth method.
Its characteristic lies in the fact that it grows by adding lines.

The conventional molecular beam growth method is a so-called vacuum evaporation method in which constituent elements are evaporated on one side and precipitated on the other side, and only flying particles are deposited on the substrate.

Although molecular beam growth is performed in a high vacuum, the molecular beam and the substrate are still unable to avoid oxidation and contamination by residual gas, which hinders Q) single crystallization when deposited on the substrate.

In other words, in the molecular beam crystal growth method, the growth process is one-sided and is susceptible to atmospheric contamination, so it can be said that there is a limit to crystallinity.

The present invention was developed in view of these problems, and is a method for making crystal raw materials that must be carefully prepared in order to allow generated molecular beams to reach a substrate without being contaminated and to cause growth on a clean substrate. This method applies molecular beams that have an etching effect on crystals to the substrate surface, and can significantly improve crystallinity without impairing the controllability of conventional molecular beam growth film thickness. Not only is it possible, but it also makes it possible to grow silicon crystals, which was previously considered impossible, and the crystal quality is equal to or better than that of other methods such as vapor phase growth.

By the way, the molecular beam source with etching action used in the method of the present invention includes H(J?, SF6. CA2゜l2
Suitable are halogens and their compounds.

Furthermore, a halide of the element to be grown can also be used; for example, AsCl3 can be used to grow GaAs.

The method of the present invention will be explained below using examples.

Example I In the case of Si, a Si substrate in a molecular beam crystal growth apparatus kept at a vacuum level of 10-9 Torr was heated to 1100°C, and this state was maintained for 1 hour. was lowered to 900'C, and HCl molecular beam was applied at 10°C per substrate surface.
It is introduced at an arrival speed of 13/i·sec.

Next, 1 molecular beam of HC is introduced, and then 101 molecular beam of Si is introduced.
5/C11t-sec.

With this method, the growth rate of Si is approximately 0.5λ at m=)
/5eCO) 4° long velocity is obtained.

Furthermore, HCJ? The molecular beam is 1150 ~
11500 is appropriate.

If the number of HC1 molecular beams is less than this, the etching effect will be small, and if it is too large, the growth rate of Si will be significantly reduced.

n-type Si obtained by the method of the present invention without doping with impurities
The carrier concentration was about 1015 crrL-3, and the hole mobility was 1500 crit-/■·sec at room temperature, showing Q times higher quality than that obtained by normal vapor phase epitaxial growth.

Note that an intermittent method in which the HCl molecular beam was introduced for 1 second at 5-second intervals using a shutter was also effective.

Example 2 In the case of GaAs, a GaAs substrate was heated to 500 to 700°C in a molecular beam crystal growth apparatus maintained at a high vacuum of 10' Torr or higher, and Ga and GaAs molecules were deposited on the GaAs substrate. At the same time, a single HC molecular beam is caused to collide with the substrate.

Ga, As2. The arrival speed of the HCIJ molecular beam is 1014/ffl·sec.

By adjusting to 1012/--sec, Ga
A s O) The growth rate is 0.1 to 10 A/sec.

Appropriately, A and s are 10 times the concentration of Ga, and the HCl concentration is approximately 1/100 times.

Crystal O) Electrical and optical properties are superior to those grown in a liquid phase, and when no impurities are added, the impurity concentration at room temperature is 1014~1015CrrL-3 Teho/L/Mobility is 1o, oOo~ 20.00 om/v -5ec
Met.

Similar good results were obtained even when all gas raw materials were used: Ga(CH3)a instead of Gap), AsH3 instead of As, and AsC73 instead of HCl.

Example 3 In the case of CuGaS2, a CuGaS2 crystal substrate placed in a molecular beam crystallization device maintained at a high vacuum of 10-9 Torr or higher was heated to 700°C, and then molecular beams of Cu, Ga, S, and I2 were introduced into the device. At the same time, CuGaS2 crystal was epitaxially grown on the substrate.

The molecular beam zero concentration of Cu, Ga-S, and I2 is each 10''/i·sec.

1014/i・sec, 1015/air-8ec
, 77i.SeC was suitable for 1012/, and a substrate temperature of 600 to 9000C was suitable.

When the crystal plane of the substrate crystal was the C plane or the (112) plane, the crystallinity was good and the surface smoothness was excellent.

As can be seen from the above examples, by introducing an etching component into molecular beam growth, it is possible to prevent oxidation and contamination due to residual gas from the incoming molecular beam, and also to clean the substrate surface. We were able to significantly improve the crystallinity of .

This method is applicable not only to the exemplified semiconductor crystal but also to LiNbO
It can also be applied to the growth of high melting point crystals such as derivatives such as No. 3, magnetic materials such as gadolinium, gallium, and garnet, and metals such as Ti and W.

Of course, it can also be applied to crystal growth that forms a heterojunction.

As explained above, the 0 method of the present invention can eliminate the disadvantages of the known 0-molecular crystal growth method without sacrificing its advantages, and improves the quality of crystals obtained by the molecular beam crystal growth method. It is also Q that has the effect of significantly increasing the

Claims (1)

[Claims] 1. Etching effect on the crystal using the molecular beam of the raw material of the crystal to be grown and the amount of 1/50 to 1/500 of the molecular beam that determines the growth rate among the Q molecular beams of the raw material. 1. A molecular beam crystal growth method characterized by simultaneously introducing a molecular beam having a chemical component having a chemical component into a substrate surface in a vacuum to grow a crystal on the substrate surface.