JPH0140512B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a semiconductor magnetoelectric effect device that allows the Hall constant and the temperature coefficient of electrical conductivity to be reduced. As magnetoelectric effect materials that utilize the Hall effect or magnetoresistive effect, semiconductors are generally used that have high carrier mobility and a large Hall constant. InSb is actually the most suitable material for this purpose, and in general, InSb formed into a thin film on a substrate by a method such as vacuum evaporation is often used as a magnetoelectric effect element. InSb
When a compound such as InSb is vacuum-deposited, it is separated into component elements and then recombined on the substrate surface, so the composition of the resulting InSb thin film is not necessarily as given by the chemical formula. In the actual state, a part with a composition close to InSb and a part with a composition almost close to In are mixed. The composition is mainly determined by the evaporation rate, substrate temperature, and evaporation time during evaporation. Note that a method is often used in which InSb is not used as a deposition source and In and Sb are evaporated separately. However, no matter which method is used, the composition of the thin film obtained on the substrate is a mixture of a collection of crystal grains almost similar to InSb and crystals with a composition almost similar to In interposed between the crystal grains. This has been confirmed. Therefore, the actual carrier mobility value of the obtained InSb thin film is about 1000 to 30000 ^{cm 2} /vs, which is 1/2 or less of the carrier mobility value of bulk InSb. Further, the Hall constant of the obtained InSb thin film is 100 to 500 cm ² /C, which is smaller than that of bulk InSb. This results in
In order to bring the values of the carrier mobility and Hall constant of the InSb thin film closer to those of bulk InSb, various changes have been made to the deposition conditions during the formation of the InSb thin film. Specifically, by changing the type of substrate, its surface treatment conditions, the substrate temperature during evaporation, the temperature of the evaporated material, and their proportions, it is possible to achieve a composition that does not necessarily have a stoichiometric composition.
It is not a matter of applying InSb to a uniform thickness;
Conditions that increase the carrier mobility of the resulting thin InSb film by changing the size and shape of InSb crystal grains and the ratio of In crystals interposed between these InSb crystal grains, and also increase the value of the Hall constant. is experimentally required. On the other hand, various experiments are being conducted to improve various properties such as carrier mobility and Hall constant by subjecting the InSb thin film once formed to appropriate heat treatment. One of these is the InSb thin film produced by a method called recrystallization, which is heated to the melting point of InSb (525°)
This is a method of increasing carrier mobility by heating to a temperature above to melt InSb and then gradually recrystallizing it. Specifically in this case
When an InSb thin film melts on a substrate, it aggregates into islands and is not isolated from each other. Therefore, methods such as coating the thin film surface with an inorganic insulating film or melting it into a narrow strip and moving it along the surface have been adopted. ing. Another method is called the annealing method, which develops and stabilizes crystal grains by heating the InSb thin film for a long time at a temperature considerably lower than the melting point of InSb. No special effects can be expected in terms of improvements in such matters. This invention was based on the above-mentioned conventional method and was obtained through further consideration.In particular, the invention is based on InSb, which makes it possible to reduce the temperature coefficient of the Hall constant and the temperature coefficient of electrical conductivity at room temperature. The present invention provides a semiconductor magnetoelectric effect element made of a heat-treated vapor-deposited thin film. This invention is based on these conventional methods and further studies, and by heating an InSb thin film in a predetermined atmosphere for a short time at a temperature slightly lower than the melting point of InSb, the crystal structure and composition of InSb are changed. By changing the electrical conductivity type, we realized p-type conductivity, and the composition ratio of In in the entire thin film is expressed as atomic percent, with InSb as the main component.
It is possible to provide a heat-treated vapor-deposited film magnetoelectric effect element with a heat treatment deposited film larger than 58%. DESCRIPTION OF THE PREFERRED EMBODIMENTS The semiconductor magnetoelectric effect device of the present invention will be described in detail below based on embodiments thereof with reference to the drawings. As mentioned above, this invention is based on InSb thin film,
This InSb thin film is heated for a short time in a predetermined atmosphere at a temperature slightly lower than the melting point of InSb to change the crystal structure and composition of the InSb thin film, and also to change its electrical conduction type, thereby changing the Hall constant at room temperature. The present invention provides a semiconductor magnetoelectric effect device having a small temperature coefficient and a small temperature coefficient of electrical conductivity, and having an In composition ratio of more than 58% in atomic percentage in the entire thin film. The inventor has proceeded with measurement and study of the characteristics of the semiconductor magnetoelectric effect device of the present invention based on two embodiments, and the present invention will be explained based on these embodiments. In the first embodiment, ferrite was used as the evaporation substrate, this ferrite substrate was maintained at a temperature of 430°C, and InSb was evaporated onto this substrate for 5 hours.
A first deposited film sample deposited in minutes is used. This first vapor-deposited film sample was heat-treated for 2 minutes at a treatment temperature of 510°C in an Ar gas atmosphere at one atmosphere.
Thereafter, it is immediately cooled at a cooling rate of 90°C/min. In this invention, it is necessary to heat the deposited film sample for a short time at a temperature slightly lower than the melting point of InSb in order to obtain the desired properties, and even when cooled,
It is necessary to process at a cooling rate of about °C/min. Figure 1 shows the first sample obtained through such heat treatment.
2 shows various characteristics of the semiconductor magnetoelectric effect device of the present invention in Examples, and shows the values of Hall constant RH, carrier mobility μ, and electrical conductivity σ with respect to temperature before and after heat treatment. In the figure, the white fixed points on each side show the state before heat treatment, and the black measurement points show the state after heat treatment. Further, C ₀ and C ₁₀₀ in the figure are temperature base lines corresponding to 0°C and 100°C, respectively. As is clear from FIG. 1, in the semiconductor magnetoelectric effect device of the present invention, the carrier mobility μ increases by several tens of percent by undergoing the above-mentioned heat treatment, and the temperature coefficients of the electrical conductivity σ and the Hall constant RH at around room temperature are It has decreased to a fraction of that. In the second example, mica was used as the deposition substrate, this mica substrate was maintained at a temperature of 430°C, and a second sample was used on which InSb+0.1In was deposited for 5 minutes. do. This second sample was heat-treated for 10 minutes at a treatment temperature of 500°C in an Ar gas atmosphere of one atmosphere, and then immediately
Cool at a cooling rate of 90℃/min. Similar to the first embodiment, in this invention, the deposited film sample is InSb.
In order to obtain the desired properties, it is necessary to heat the material for a short time at a temperature slightly lower than the melting point of the material, and even during cooling, it is necessary to perform the treatment at a cooling rate of about 90° C./min. Figure 2 shows the second image obtained through such heat treatment.
This figure shows various characteristics of the semiconductor magnetoelectric effect device of the present invention in Examples, and each reference numeral in the figure is the same as that in FIG. 1. By subjecting the second sample to the heat treatment described above, the semiconductor magnetoelectric effect device of the present invention in the second embodiment has a tendency that its carrier mobility μ slightly decreases at around room temperature, but the electrical conductivity The temperature coefficients of the degree σ and the Hall constant R _H near room temperature are reduced to a fraction of a fraction. For the first sample used in the first example, the heat treatment time is 2 minutes, 6 minutes, and 10 minutes as parameters, respectively, and the heat treatment temperature T (℃) and the carrier mobility μ of the magnetoelectric effect element obtained by performing the heat treatment are The results shown in FIG. 3 are obtained. In the figure, μ ₀ indicates the carrier mobility before heat treatment,
□, △, □ are heat treatment times of 2 minutes, 6 minutes and
This is a code indicating 10 minutes. In this case, as mentioned above, the cooling rate is set at 90°C/min. As is clear from FIG. 3, when the heat treatment time at the same heat treatment temperature is increased, the carrier mobility of the magnetoelectric effect element increases. Further, when the heat treatment time is held constant and the heat treatment temperature is varied, there is a maximum value in the carrier mobility when the heat treatment is performed at approximately 510°C. This changes the sample to InSb to deviate the Sb
This is the maximum value corresponding to each heating time obtained under experimental conditions due to short heating at a high temperature close to the melting point of. The heat treatment according to this invention
The desired characteristics are obtained by heating for a short time at a high temperature close to the melting point of InSb, and it is desirable that the heating temperature be as high as the conditions allow. It is also desirable that the heating time be as short as the conditions allow; if the heating time is prolonged, the In composition portions that exist in island form on the composition close to InSb of the vapor-deposited thin film will enter into the composition portion of the vapor-deposited film close to InSb. It will damage the characteristics. Regarding the second sample used in the second example, the heat treatment time T (°C) and the carrier mobility of the magnetoelectric effect element obtained by applying the heat treatment using the respective heat treatment times of 2 minutes, 6 minutes, and 10 minutes as parameters. When the relationship with μ is shown, the results shown in FIG. 4 are obtained. In the figure, μ ₀ represents the carrier mobility before heat treatment, and □, △, and □ represent heat treatment times of 2 minutes and 6 minutes, respectively.
This is a code indicating minutes and 10 minutes. As is clear from Figure 4, for example, the heat treatment temperature
As the heat treatment time increases at 510°C, the carrier mobility μ of the magnetoelectric effect element decreases.
The rate of decrease is particularly large when the heat treatment time is 10 minutes. However, at a heat treatment temperature of 500° C., the tendency for the carrier mobility μ of the magnetoelectric effect element to decrease, which was observed when the heat treatment time was increased from 2 minutes to 6 minutes, was reversed after the heat treatment time was 10 minutes. This is due to the fact that as the heating time increases, the In composition part that exists in island form on the composition close to InSb of the deposited thin film enters the composition part of the deposited film close to InSb, and the characteristics change. This shows that the heating temperature for 2 minutes and 6 minutes has decreased from 510°C to approximately 500°C. For short heating times of 2 minutes and 6 minutes, the same temperature characteristics in the opposite direction as the first sample are shown. The first and second aspects of this invention having such characteristics
Regarding the semiconductor magnetoelectric effect element in the example of
40 μm in diameter by means of a wire microanalyzer.
The composition ratios of In and Sb before and after heat treatment were measured for each measurement area, and the results shown in Table 1 were obtained. The sample shown in (1) in the table is a semiconductor magnetoelectric effect element according to the first embodiment of the present invention whose characteristics are shown in FIGS. 1 and 3, and the symbol A0 indicates each measured value before heat treatment. , symbol A1 corresponds to each measurement value after the heat treatment. or,
The samples shown in (2) in the table are semiconductor magnetoelectric effect devices according to the second embodiment of the present invention, whose characteristics are shown in FIGS. 2 and 4, respectively. Measured values, symbol C1, correspond to each measured value after the heat treatment.

[Table] As is clear from Table 1, the semiconductor magnetoelectric effect device of the present invention is capable of reducing the temperature coefficient of the Hall constant and the temperature coefficient of electrical conductivity at room temperature by heat treatment. As shown in the second embodiment, the In composition ratio in the entire heat-treated vapor deposited thin film mainly composed of InSb is approximately 58% or more in terms of atomic percentage. The magnetoelectric effect element of the present invention, in which the composition ratio of In in the entire heat-treated vapor-deposited film mainly composed of InSb is set as described above, has a flat Hall constant R _H at around room temperature as described above. The temperature coefficient of electrical conductivity σ also becomes smaller. When the temperature coefficient of electrical conductivity σ becomes smaller, the current value that can be taken when passing a current through a semiconductor magnetoelectric effect element takes into consideration the safety level against temperature, and the degree of freedom in the use of the magnetoelectric effect element increases. become. The magnetoelectric effect element having the composition obtained in this invention can be produced only by the method described in this application, and the magnetoelectric effect element having this composition cannot be produced directly. This is because even if the amount of Sb is reduced during vapor deposition, the product will only have a reduced amount of In crystal content as mentioned above.
This is because the composition of the InSb portion remains unchanged. In general, it is difficult to control the composition of this type of semiconductor magnetoelectric effect element at the time of vapor deposition, and by controlling the composition in the subsequent heat treatment step using the means described in this application, it is possible to easily achieve the desired effect with high precision. A magnetoelectric effect element with a composition of can be obtained. Although the present invention has been described above based on the first and second embodiments, in reality, thin films with various characteristics can be obtained depending on the vapor deposition conditions when creating the vapor-deposited film, and each thin film is subjected to heat treatment. By selecting the respective conditions, it is possible to obtain a magnetoelectric effect element having even better electrical characteristics. In the embodiment of this invention, the carrier mobility μ ₀ before heat treatment is
For materials below 10000cm ² /v・s, the value of carrier mobility μ decreases by several times compared to the value before heat treatment due to heat treatment.
It increases by 10% to several 100%, and moreover, the values of the temperature coefficient of the electrical conductivity σ and the Hall constant R _H near room temperature become several times lower. Further, if the carrier mobility μ ₀ before heat treatment is 10000 cm ² /v·s or more, the value of the carrier mobility μ may increase or decrease depending on the heat treatment. However, in any case, in the semiconductor magnetoelectric effect device of the present invention, the electrical conductivity σ and the Hall constant at around room temperature
The value of the temperature coefficient of R _H has been reduced by a factor of several. In addition, although the atmosphere for heat treatment in this invention is Ar in the examples,
In addition, neutral or reducing gases such as N ₂ and H ₂ can be used, in which case the pressure is 0.
~ several atmospheres is desirable. Further, heat treatment can be performed even in an oxidizing gas atmosphere at low pressure. The heat treatment temperature was as specifically explained in each example.
It is preferable to carry out the heat treatment at a temperature below the melting point of InSb, that is, in the temperature range of 520 to 400°C, and the heat treatment time is in the range of 2 minutes to 30 minutes. The mechanism by which the carrier mobility μ, electrical conductivity σ, Hall constant R _H , etc. of the InSb thin film changes as a result of heat treatment in the semiconductor magnetoelectric effect device of the present invention is described below. It can be explained theoretically. In other words, in the semiconductor magnetoelectric effect device of the present invention, the Hall constant and the temperature coefficient of electrical conductivity can be reduced due to the development of crystal grains due to heating during heat treatment, but the main reason is that crystal grains are developed by heat treatment. In
By dissipating Sb to the outside, the composition ratio of In in the entire heat-treated vapor-deposited thin film is increased, which in turn increases the ratio of acceptor impurity to donor impurity, and conductively converts the magnetoelectric effect element into a p-type semiconductor. This is because it has been Generally, in InSb, the electron mobility is much larger than the hole mobility, so even if there are more acceptors than donors, it is known that it behaves as an n-type semiconductor at high temperatures and as a p-type semiconductor at low temperatures. ing. At a temperature near the point where the conductivity type changes, the Hall constant of InSb changes from a negative value to a positive value, and at a slightly higher temperature at this conversion point, the Hall constant becomes flat against temperature changes. In the semiconductor magnetoelectric effect device of the present invention, the Hall constant R _H at around room temperature becomes flat with respect to temperature by adjusting the amount of impurities in the thin film mainly composed of InSb and changing the composition as described above. There is. The electrical conductivity σ of the crystal is the Hall constant R _H
It is inversely proportional to , and if the temperature coefficient of the Hall constant R _H is small, the temperature coefficient of the electrical conductivity σ is also small. Further, in the semiconductor magnetoelectric effect device of the present invention, the carrier mobility μ may hardly change or may increase or decrease if the crystal structure and impurity distribution are changed by the heat treatment as described above. The present invention relates to a semiconductor magnetoelectric effect element in which temperature changes in Hall constant R _H and electrical conductivity σ are reduced, and impurity distribution control is achieved with high accuracy through heat treatment in which the heat treatment temperature and heat treatment time are set to predetermined values. The composition ratio of In in the entire deposited thin film mainly composed of InSb is set to a value greater than 58% in atomic percentage. In the description of the embodiments of the semiconductor magnetoelectric effect device of the present invention, the heat-treated vapor-deposited thin film that is heat-treated is mainly composed of InSb, but Ga, As, Ge, etc. are added in a few percent to the InSb.
The present invention can be realized even in a state in which there is some degree of contamination. As explained in detail above, according to the present invention, it is possible to reduce the temperature coefficient of Hall constant and the temperature coefficient of electrical conductivity at around room temperature, and increase the current value that can be passed in consideration of temperature safety. This makes it possible to provide a semiconductor magnetoelectric effect device that is mainly composed of InSb, which can produce a heat-treated thin film, and in which the composition ratio of In in the entire heat-treated thin film is 58% or more in atomic percentage.

[Brief explanation of drawings]

FIG. 1 shows the first diagram of the semiconductor magnetoelectric effect device of the present invention.
FIG. 2 is a diagram showing various characteristics relative to temperature of the second embodiment of the semiconductor magnetoelectric effect device of the present invention, and FIG. 3 is a diagram showing various characteristics of the semiconductor magnetoelectric effect device of the present invention relative to temperature. A diagram showing the relationship between heat treatment temperature and carrier mobility using heating time as a parameter in the first embodiment, and FIG. FIG. 3 is a diagram showing the relationship between temperature and carrier mobility. T: temperature, R _H : Hall constant, μ: carrier mobility, σ: conductivity, μ ₀ : carrier mobility before heat treatment.

Claims (1)

[Claims] 1 Consisting of a heat-treated vapor-deposited thin film mainly composed of InSb,
The composition ratio of In in the entire thin film is 58% in atomic percentage.
A semiconductor magnetoelectric effect element characterized by being larger than .