JPH0652720B2 - Vapor growth method of lanthanoid element-doped semiconductor - Google Patents

Description

TECHNICAL FIELD The present invention relates to crystal growth, particularly epitaxial growth, of III-V group semiconductors doped with a lanthanoid element. A lanthanoid element-doped III-V group semiconductor is a material that exhibits a sharp emission spectrum based on a core transition peculiar to a lanthanoid ion while maintaining electrical characteristics as a semiconductor. It is a material for light emitting devices such as lasers and light emitting diodes, and nonlinear optics. It is useful as a material.

(Problems to be Solved by Prior Art and Invention) Lanthanoid elements such as neodymium (Nd) and erbium (Er) are used as materials for solid-state lasers. In particular, Nd-doped yttrium aluminum garnet (YAG)
Is widely used as a laser material for measurement or processing. These solid-state lasers have a structure as shown in FIG. 9, for example. That is, a rod-shaped YAG crystal containing Nd is sandwiched from both sides by an excitation lamp, and light emitted from the excitation lamp is collected on this rod, and Nd ions contained therein are photoexcited to cause laser oscillation.
Some use a light source such as a semiconductor laser or a light emitting diode instead of the excitation lamp, but since this structure is essentially composed of discrete parts, (1) the size of the laser itself cannot be reduced, (2) The conversion efficiency from input energy to laser output is as low as 0.1%,
There were drawbacks such as.

In order to overcome the above-mentioned drawbacks, a semiconductor laser or a light emitting diode in which a semiconductor is doped with lanthanoid ions and light is emitted by current injection has been proposed (Helmut).
Enn and Juerger Schneider: German Patent DE 3344138A1 published June 14, 1984). Its structure is shown in FIG. If laser oscillation can be realized by current injection using this structure, not only can monochromaticity and wavelength stability similar to the emission line of ordinary solid-state lasers be secured, but (1) an excitation lamp for photoexcitation is not required and laser There are merits such as downsizing of the main body and (2) increase of conversion efficiency from electric energy to laser output up to several tens of percent.

As described above, the technique of doping a III-V semiconductor with a lanthanoid element greatly contributes to high performance of a light emitting device, but the conventional method of doping a semiconductor with a lanthanoid element has been limited to the following three methods. That is, (1) a method of using ion implantation and subsequent annealing together, (2) a method of adding a lanthanoid element to a melt for liquid phase growth and performing epitaxial growth, (3) a molecular beam epitaxy (MBE) method,
It is a method of performing epitaxial growth while doping lanthanoid ions.

These methods have the following drawbacks. First
According to the method (1), it is difficult to selectively dope a thin region (~ 0.1 μm) such as the active layer of the structure shown in FIG. We have to add processes such as annealing, which increases the number of processes,
It's inconvenient. With the method (2), it is possible in principle to fabricate the structure shown in FIG. 10.However, since the lanthanoid element is extremely easy to oxidize, the lanthanoid element is added to the growth melt before the growth. All the steps until the end must be performed in a glove box replaced with an inert gas, and the work efficiency is significantly reduced as compared with normal liquid phase growth. In addition, even if the growth is carried out with sufficient care to prevent the mixing of oxygen and moisture, the lanthanoid ion-doped semiconductor produced by liquid phase growth generally has a low luminous efficiency of the lanthanoid ion, and the crystallinity is low. Light emission from deep levels due to defects is usually strongly observed. Also,
The small segregation coefficient of the lanthanoid element from the liquid phase to the solid phase also makes doping difficult. The structure shown in Fig. 10 can also be produced by the method of (3) .However, in order to dope the lanthanoid element having a strong oxidizing property by the MBE method, it is necessary to maintain an ultrahigh vacuum especially in the growth apparatus. In addition, the device becomes expensive and a lot of labor is required for maintenance. Further, in general, a refractory metal such as a lanthanoid element needs to have a high evaporation source temperature, and therefore a special container or the like needs to be devised.

As a method for solving the above-mentioned drawbacks, a method has been proposed in which a gas containing a vapor of an organic compound of a lanthanoid element is added to a reaction gas of a vapor phase growth system to vapor-deposit a lanthanoid element-doped semiconductor. However, even in this method, when the vapor of the organic compound of the lanthanoid element is introduced into the vapor phase growth reactor by using hydrogen gas, in addition to the lanthanoid element to be added, transition of iron, manganese, chromium, nickel, etc. There is a problem that the metal is taken into the epitaxial growth layer at a concentration of 10 ^-15 to 10 ^-16 cm ^-3 or more. These impurities react with the organic compound of the lanthanoid element to be added and the constituent elements (mainly the transition metal) of the piping material used in the gas piping in a hydrogen atmosphere, and the substitution reaction between the lanthanoid element and the constituent element of the piping material occurs. It is considered that some of the constituent elements of the piping material occur in the form of organic compounds and are transported in the gas.

(Object of the Invention) The object of the present invention is to produce a lanthanoid element by metalorganic chemical vapor deposition (MOCVD), which can easily produce multi-element mixed crystals, double heterostructures, superlattice structures, etc. It is to provide a method for producing a doped III-V compound.

Further, according to the present invention, the concentration of transition metals such as iron, manganese, chromium, and nickel is very low, and the efficiency of light emission based on the core transition of lanthanoid elements is high.
It is to provide a method for producing a III-V group compound.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention uses a gas containing a vapor of an organic compound of a lanthanoid element as a reaction gas of a vapor phase growth system in the vapor phase growth of a III-V group compound. And the gas is circulated on the substrate to contain the lanthanoid element.
The gist of the invention is a vapor phase growth method of a lanthanoid element-doped semiconductor, which comprises forming a III-V group compound on the substrate.

Therefore, the present invention provides a suitable carrier for the vapor of an organic compound containing a lanthanoid element such as ytterbium (Yb), erbium (Er), neodymium (Nd) and praseodymium (Pr) during the growth of III-V compounds by MOCVD. Gas was introduced into the reaction tube for crystal growth, and lanthanoid element doping III was performed.
The most main feature is to produce a group V compound.
According to this method, a structure in which a helantanoid element such as a double hetero or superlattice is uniformly or selectively doped in a specific layer can be extremely easily prepared, and therefore various applications, particularly a lanthanoid element is included. Its practical effects are extremely large, such as the fact that a light emitting device and a nonlinear optical device can be easily manufactured.

Furthermore, the present invention provides ytterbium (Yb), erbium (Er), neodymium (N) in vapor phase growth of III-V compounds.
d), a vapor of an organic compound containing a lanthanoid element such as praseodymium (Pr), a carrier gas containing at least one of rare gases such as helium and argon or an inert gas such as nitrogen as a part or all of the components. The main feature is to introduce a lanthanoid element-doped III-V compound having a low concentration of transition metal impurities such as iron, manganese, chromium, and nickel into the reaction tube for crystal growth. According to this method, it is possible to prevent the reaction between the organic compound of the lanthanoid element and the constituent element of the gas piping material described in the section of the prior art, and thus the formation of the organic compound containing the constituent element of the gas piping material is prevented. Can be prevented. For this reason, the concentration of transition metal impurities is extremely low compared to the case where the vapor of an organic compound containing a lanthanoid element is introduced into the reaction tube using pure hydrogen only. Therefore, the concentration of non-radiative recombination centers is low and A highly efficient lanthanoid element-doped III-V group compound can be produced.

Next, examples of the present invention will be described. Needless to say, the embodiment is merely an example, and various modifications and improvements can be made without departing from the spirit of the present invention.

(Embodiment 1) FIG. 1 shows an outline of a MOCVD apparatus used for carrying out the present invention. Taking InP as the substrate and growing the lanthanoid element-doped InP on it,
The growth method will be described with reference to the drawings. First pipe 8
The hydrogen gas for dilution purified by is sent. Then, the InP substrate 15 is heated by heating the susceptor 14 in the quartz reaction tube 13 by high frequency heating (RF coil 12). InP substrate is about 300
When the temperature reaches ℃, phosphine (PH ₃ ) (diluted with 20% hydrogen) is introduced into the reaction chamber through the pipe 9 to prevent the evaporation of P from the substrate. When the InP substrate reaches a predetermined temperature, triethylindium 17 is introduced into the reaction tube 13 by the carrier hydrogen gas sent by the pipe 10. Further, triscyclopentadienyl ytterbium [Yb (C ₅ H ₅ ) ₃ ] 19 which has been heated to a predetermined temperature by a heater of 18 in advance is passed through a pipe heated by a heater 20 by hydrogen sent from 11 to a reaction tube. Introduce to 13. At this time, the temperature of the heater 20 is 10 times higher than the temperature of the container of triscyclopentadienyl ytterbium.
The temperature is raised from 50 ℃ to 50 ℃ to prevent the deposition of triscyclopentadienyl ytterbium in the piping. As described above, if triethylindium and triscyclopentadienyl ytterbium are introduced for a predetermined time, a desired ytterbium-doped InP crystal grows. For example, the InP substrate is kept at a temperature of 650 ° C, and hydrogen for dilution is supplied through the pipe 8
Flow at 00 / min, keep triethylindium at 30 ℃,
300cc / min of hydrogen is flowed through this, and phosphine is added at 300cc / min.
(20% hydrogen dilution) was passed and triscyclopentadienyl ytterbium was kept at 223 ° C.
A minute amount of hydrogen was flowed, and InP crystal growth was performed for 180 minutes. When the grown crystal was evaluated by using both secondary ion mass spectrometry and chemical analysis, InP crystal doped with 3.6 × 10 ¹⁸ / cm ³ of ytterbium was grown to a thickness of 6 μm.

This crystal was kept at 77K in liquid nitrogen, and was excited by light with a wavelength of 633 nm from a helium neon laser, and the photoluminescence was measured. The spectrum shown in Fig. 2 was obtained, and ytterbium with high-quality optical characteristics was obtained. It was found that the doped InP crystal was growing.

Example 2 The process of Example 1 was used except that the temperature of the triscyclopentadienyl ytterbium container was varied between 50 ° C and 250 ° C. The ytterbium concentration in the ytterbium-doped InP prepared under these conditions was investigated by using both secondary ion mass spectrometry and chemical analysis. As a result, the ytterbium container temperature and the ytterbium concentration in the InP crystal as shown by the solid line in Fig. 3 were compared. A relationship was obtained.

(Example 3) The process of Example 2 was used except that the flow rate of hydrogen flowing in the triscyclopentadienyl ytterbium container was changed to 300 cc / min. When the relationship between the container temperature of triscyclopentadienyl ytterbium and the ytterbium concentration in the InP crystal was examined, the relationship shown by the broken line in FIG. 3 was obtained.

As can be seen from the above results, in order to dope ytterbium into InP at a concentration effective as an emission center,
50 containers of triscyclopentadienyl ytterbium
Must be kept above ℃. Further, if the temperature of the triscyclopentadienyl ytterbium container is maintained at a temperature higher than 250 ° C., there is a high possibility that it will decompose in the container or in the middle of the pipe transported to the reaction tube, and effective doping cannot be performed.

(Example 4) Triscyclopentadienyl ytterbium was replaced with triscyclopentadienyl erbium, and the container temperature was changed.
The process of Example 1 was performed by changing the temperature between 50 ° C and 300 ° C. When the concentration of erbium doped in the InP crystal was examined when the flow rate of hydrogen flowing in the container of triscyclopentadienyl erbium was 100 cc / min and 300 cc / min, the relationship shown in FIG. 4 was obtained. The solid line indicates the flow rate of hydrogen flowing in the container of triscyclopentadienyl erbium is 100 cc /
In the case of minutes, the broken line is the case where the flow rate of hydrogen flowing into the container of triscyclopentadienyl erbium is 300 cc / min. The erbium-doped InP crystal produced under these conditions was kept at 77 K in liquid nitrogen and excited with light having a wavelength of 633 nm from a helium neon laser, and the spectrum shown in FIG. 5 was obtained.

Example 5 The same process as in Example 4 was used, except that triscyclopentadienyl erbium was replaced with triscyclopentadienyl neodymium. By changing the temperature of the triscyclopentadienylneodymium container between 150 ° C and 350 ° C, the flow rate of hydrogen flowing in the triscyclopentadienylneodymium container is 10
When experiments were conducted for 0 cc / min and 300 cc / min, the relationship shown in FIG. 6 was obtained. The solid line is for a hydrogen flow rate of 100 cc / min flowing into the triscyclopentadienyl neodymium container, and the broken line is for 300 cc / min.

Example 6 The same process as in Example 4 was used, except that triscyclopentadienyl erbium was replaced with triscyclopentadienyl praseodymium. Triscyclopentadienyl praseodymium container temperature was changed between 180 ℃ and 350 ℃, and experiments were conducted for hydrogen flow rates of 100 cc / min and 300 cc / min in the triscyclopentadienyl praseodymium container. , The relationship of FIG. 7 was obtained. The solid line is for a hydrogen flow rate of 100 cc / min flowing into the triscyclopentadienyl praseodymium container, and the broken line is for 300 cc / min.

(Example 7) Under the growth conditions similar to those in Example 4, the hydrogen gas supplied to the container of triscyclopentadienylerbium was replaced with helium, argon, and nitrogen to prepare crystals. Helium flowing in a container of triscyclopentadienyl erbium,
Or the flow rate of argon or nitrogen is from 2cc / min to 200cc / min.
Changed between minutes. When examined using secondary ion mass spectrometry, the erbium concentration does not show a significant change compared with the case where hydrogen is used in any gas, whereas iron, manganese, chromium, nickel, etc. The concentration of the transition metal impurities of was less than 1/10. Moreover, when the gas to be flown into the container of triscyclopentadienyl erbium was kept at 77K with erbium-doped InP grown as helium, argon, or nitrogen, and excited by light with a wavelength of 633 nm from a helium neon laser, 1.
Emission from erbium was observed at 54 μm. The emission intensity of erbium-doped InP prepared by flowing pure hydrogen into a container of triscyclopentadienylerbium.
It was more than 10 times.

(Example 8) Triscyclopentadienyl erbium was replaced with trismethylcyclopentadienyl erbium [(CH ₃ -C ₅ H ₅ ) ₃ Er], and a gas flowing into a trismethylcyclopentadienyl erbium container was used. The same process as in Example 4 was used, except that helium, argon, or nitrogen was used. Trismethylcyclopentadienyl erbium container temperature
The flow rate of gas flowing into the trismethylcyclopentadienyl erbium container is changed between 30 ° C and 100 ° C by 200 cc /
When the experiment was conducted as a minute, the relationship shown in FIG. 8 was obtained. This relationship did not change when the type of gas flowing into the trismethylcyclopentadienyl erbium container was helium, argon, or nitrogen. The impurities in the grown crystal were examined by using secondary ion mass spectrometry. As a result, the crystals produced by the method described in Example 7 and transition metal impurities such as iron, manganese, chromium, and nickel with a low concentration were obtained. It was observed. When this crystal was kept at 77 K and excited with light of a wavelength of 633 nm from a helium neon laser, luminescence from erbium was observed at 1.54 μm. Its luminescence intensity was produced by the method described in Example 7. It was about the same as the crystal.

As is clear from the above results, according to the present invention, 10 ¹⁵
cm lanthanide element in the desired range between ^-3 to 10 ¹⁹ cm ^-3 units can be controlled with good doped epitaxial layer, high quality which can not be obtained by doping a prior done in that ion implantation or liquid phase growth It was found that the above lanthanoid-doped III-V group compound crystal was obtained.

Although the above results describe InP growth on an InP substrate, the present invention is directed to III-V group compounds other than InP, such as GaAs and G.
It goes without saying that the invention can be applied to aP, AlAs, AlP and mixed crystals thereof in general. Also, as a doping raw material, a lanthanoid triscyclopentadienyl compound
(C ₅ H ₅ ) ₃ Ln (Ln: lanthanoid element), trismethylcyclopentadienyl compound (CH ₃ -C ₅ H ₅ ) ₃ Ln other than (C ₅ H ₅ ) _{2
LnCl, (CH 3 C 5 H} 4) 2 LnCl, _{[(C 5 H 5) 2 LnCH} 3 ] _{2, (C 5 H 5)} 2
LnCC ₆ H ₅ , (C ₅ H ₅ ) ₂ LnC CR (R = C ₆ H ₅ , nC ₄ H ₉ , nC ₆ H ₁₃ ,
cC ₆ H _{11), [(C 5 H 5) 2 Ln} CC (CH 3) 3 ] _2, etc. can be used.

(Effects of the Invention) As described above, the lanthanoid element-doped II of the present invention
According to the vapor phase growth method of the IV compound, since the organic compound of the lanthanoid element is used as the dopant to perform the doping during the epitaxial growth, it is possible to accurately obtain a complex structure such as a double hetero structure or a superlattice structure with high accuracy. Can be doped with a desired concentration of the lanthanoid element between 10 ¹⁵ cm ^-3 and 10 ¹⁹ cm ^-3 to obtain a high-quality lanthanoid-doped III-V compound crystal. By using this method, the lanthanoid element can be selectively doped into the active layer having the double hetero structure, so that a current injection type semiconductor laser using the lanthanoid element as a light emitting source can be realized.

Further, the lanthanoid element-doped III-V group compound and the vapor phase growth method of the present invention are such that when an organic compound of a lanthanoid element is used as a dopant for epitaxial growth, a container of the organic compound of a lanthanoid element such as helium or argon is used. Since a carrier gas containing noble gas or at least one kind of inert gas such as nitrogen as a part or all of the components has been decided to flow, compared with the case where pure hydrogen alone is flowed into the container of the organic compound of the lanthanoid element. The concentration of transition metal impurities such as iron, manganese, chromium, and nickel is less than one tenth. Along with this, the emission intensity from the doped lanthanoid element is
Compared with the case of using pure hydrogen, it is 10 times or more, and it has the effect of realizing a highly efficient light emitting diode or semiconductor laser.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the constitution of an apparatus for realizing the vapor phase growth method of the present invention, FIG. 2 is an emission spectrum of an ytterbium-doped InP layer produced by the vapor phase growth method of the present invention, and FIG. The temperature of the pentadienyl ytterbium container and
It shows the relationship of ytterbium concentration in InP. The solid line in the figure shows the hydrogen flow rate to the triscyclopentadienyl ytterbium container at 200cc / min, and the broken line shows the hydrogen flow rate to the triscyclopentadienyl ytterbium container.
It shows the case of 300cc / min. Fig. 4 shows the relationship between the temperature of the triscyclopentadienyl erbium container and the concentration of erbium in InP. The solid line in the figure is the broken line when the hydrogen flow rate in the triscyclopentadienyl erbium container is 100cc / min. Indicates the case where the flow rate of hydrogen flowing into the triscyclopentadienyl erbium container is 300 cc / min. FIG. 5 shows erbium-doped InP prepared by the vapor phase epitaxy method of the present invention.
The emission spectrum of the layer, Fig. 6 shows the relationship between the temperature of the container of triscyclopentadienyl neodymium and the concentration of neodymium in the InP layer. The solid line in the figure shows the flow rate of hydrogen flowing in the container of triscyclopentadienyl neodymium at 100cc. / Minute,
The broken line shows the case where the flow rate of hydrogen flowing into the triscyclopentadienyl neodymium container is 300 cc / min. Fig. 7 shows the relationship between the temperature of the triscyclopentadienyl praseodymium container and the concentration of praseodymium in the InP layer. The solid line in the figure indicates that the hydrogen flow rate in the triscyclopentadienyl praseodymium container is 100cc / min. The broken line shows the case where the flow rate of hydrogen flowing into the triscyclopentadienyl praseodymium container is 300 cc / min. Fig. 8 shows the relationship between the container temperature of trismethylcyclopentadienyl erbium and the concentration of erbium in the InP layer, Fig. 9 is the conventional solid-state laser using an excitation lamp, and Fig. 10 is the lanthanoid element doping that causes light emission by current injection. A semiconductor laser is shown. 1 ... Pumping cavity 2 ... Laser rod 3 ... Excitation lamp 4 ... Electrode 5 ... P-type layer 6 ... Active layer doped with lanthanoid element 7 ... N-type layer 8 ... Sending hydrogen for dilution Gas inlet 9 …… Gas inlet for sending mixed gas of phosphine and hydrogen 10 …… Hydrogen system for transporting triethylindium 11 …… Hydrogen system for transporting organic compound of lanthanoid element 12 …… RF coil 13 …… Transparent quartz Tube 14 …… SiC coated carbon susceptor 15 …… InP substrate 16 …… Thermocouple 17 …… Triethylindium 18 …… Heater for heating organic compound of lanthanoid element 19 …… Organic compound of lanthanoid element 20 …… … A heater that heats the pipe

Claims (1)

[Claims] 1. In vapor phase growth of a III-V group compound, a gas containing a vapor of an organic compound of a lanthanoid element is added to a reaction gas of a vapor phase growth system, and the gas is circulated on a substrate to A vapor-phase growth method for a lanthanoid element-doped semiconductor, comprising forming a III-V group compound containing a lanthanoid element on the substrate.