JP2702889B2 - Semiconductor layer crystal growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a crystal of a semiconductor layer.

[0002]

2. Description of the Related Art A semiconductor device generally has a semiconductor structure comprising one or more semiconductor layers formed on a substrate. Conventionally, such a semiconductor layer has been formed by a liquid phase epitaxy method (LPE method) or the like. In recent years, a metal organic vapor phase epitaxy method (MOVPE method) or a molecular beam epitaxy method (MB
The semiconductor layer is being formed using E method).

For example, in the case of a GaAs-based or InP-based III-V compound semiconductor used for a high-speed electronic device or a semiconductor laser, the semiconductor layer is formed of a GaAs substrate or an I-type semiconductor.
The epitaxial growth can be favorably performed on the nP substrate by the MOVPE method or the like. The obtained semiconductor layer has sufficiently satisfactory characteristics.
Semiconductor layers composed of III-V group compound semiconductors of s-type or InP-type have been mass-produced and used for high-speed devices and semiconductor lasers. According to the current MOVPE method, a semiconductor layer that almost meets needs can be formed.
It is considered that a technique for forming an InP-based or InP-based semiconductor layer is almost established.

On the other hand, II-
In the case of a group VI compound semiconductor, it is generally very difficult to form a semiconductor layer having good characteristics. For this reason, a semiconductor device using a semiconductor layer made of a II-VI compound semiconductor is not yet in a practical stage. Also, I
Even with II-V group compound semiconductors, it is also difficult to obtain a nitrogen-containing GaN-based semiconductor layer having good characteristics.

For example, it has been reported that a laser using a II-VI group compound semiconductor was continuously oscillated at room temperature for the first time (for example, N. Nakayama et al., Electron. Le.
tt.29 (1993) 1488). In this report, the lifetime of a semiconductor laser is on the order of seconds.

This report reports that ZnMgSS
It discloses that a semiconductor layer made of e is grown on a GaAs substrate. According to the MBE method reported in this report, in order to obtain p-type ZnSe having a low resistance, a nitrogen plasma doping technique (for example, K. Ohkawa et al., J. Cryst.
Growth 117 (1991) 375). This plasma doping technique has attracted attention as a promising technique for forming a II-VI group compound semiconductor layer, and is being developed.

[0007]

In this MBE method, the constituent elements and doping materials constituting the semiconductor are blown onto the substrate as a molecular beam to grow crystals, so that the degree of vacuum during the growth is as high as 10 ^-6 Torr. It is kept in a vacuum. The growth temperature is optimized at about 300 ° C.

However, a semiconductor layer made of ZnSe formed at a low temperature of about 300 ° C. has a thermal history (eg, a step of forming a passivation film, a step of forming a SiO ₂ film for current confinement by a CVD method) received in a normal semiconductor device manufacturing process. 300 received in the process and the alloy process for forming electrodes
(A heat history of about 400 ° C. to about 400 ° C.) greatly reduces the quality of the semiconductor layer. For example, the emission intensity of photoluminescence is extremely reduced. Therefore, the current confining Si
By forming a polyimide film instead of the O ₂ film, or by forming a non-alloy type electrode which does not require an alloying step, the semiconductor layer is not subjected to a high temperature thermal history.
However, it is extremely difficult to mass-produce semiconductor devices having high reliability using such a substitute process.

In general, the group III-V semiconductor layer has a thickness of about 60
Considering that it is grown at 0-800 ° C., this M
The growth temperature of the BE method is extremely low. Considering that a bulk single crystal of a group II-VI compound semiconductor is usually formed at about 1000 ° C., it is considered preferable to grow a semiconductor layer at a higher temperature in this MBE method.

However, when the growth temperature is increased to about 400 to 500 ° C. in the MBE method, the quality of the obtained semiconductor layer is greatly impaired.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for growing a semiconductor layer having high crystal quality.

[0012]

According to the present invention, there is provided a method for growing a crystal of a semiconductor layer, comprising a plurality of source gases containing elements constituting the semiconductor layer and at least one of which is an organometallic compound. Introducing the source gas into the growth chamber, and decomposing the source gas near the surface of the heated substrate while maintaining the growth pressure in the growth chamber at 1 atm or higher, thereby forming the semiconductor layer on the substrate. Epitaxial growth step, whereby the above object is achieved.

The semiconductor layer is composed of at least first and second constituent elements, and at the temperature of the heated substrate, the saturated vapor pressure of the first constituent element is higher than the saturated vapor pressure of the second constituent element. The partial pressure of the source gas containing the first constituent element is higher than the partial pressure of the source gas containing the second constituent element among the partial pressures constituting the growth pressure. Is preferred.

When the semiconductor layer is heated while being kept at a low pressure of 1 atm or less, at least one of the elements constituting the semiconductor layer is substantially desorbed from the semiconductor layer and the temperature is higher than the decomposition temperature at which the semiconductor layer starts to decompose. Preferably, the substrate is heated at a temperature of

[0015] The semiconductor layer may include one of a II-VI compound semiconductor, a III-V semiconductor, and a chalcopyrite-based semiconductor.

One of the constituent elements may contain at least one of selenium and sulfur.

[0017] The constituent element may contain nitrogen.

The method for growing a semiconductor multi-layer crystal according to the present invention may include a plurality of first source gases containing elements constituting the first semiconductor layer, at least one of which is an organometallic compound. Introducing the first source gas into the growth chamber, and maintaining the pressure in the growth chamber at the first growth pressure while transferring the first source gas near the surface of the substrate heated to the first temperature. A step of epitaxially growing the first semiconductor layer on the substrate by decomposing; and a plurality of second source gases containing elements constituting the second semiconductor layer, at least one of which is an organic gas. Introducing a plurality of second source gases, which are metal compounds, into the growth chamber; and maintaining the pressure in the growth chamber at a second growth pressure while maintaining the first growth pressure of the substrate heated to a second temperature. Near the surface of the semiconductor layer By decomposing raw material gas had encompass epitaxially growing a semiconductor layer of the second to the first semiconductor layer, To Sukunakumo first
One of the growth pressure and the second growth pressure is 1 atm or more, whereby the above object is achieved.

Before the step of introducing the plurality of second source gases into the growth chamber, the method may further include the step of reducing the pressure of the reaction chamber to substantially 1 atm or less.

[0020] The growth chamber includes a first sub-growth chamber and a second sub-growth chamber, said first semiconductor layer is grown at a sub-growth chamber the first, the said second semiconductor layer It may be grown in the second sub-growth chamber .

[0021] One of the first growth pressure and the second growth pressure may be 1 atm or more, and the other may be 1 atm or less.

The semiconductor layer grown at a growth pressure of 1 atm or more is composed of at least first and second constituent elements, and the saturated vapor pressure of the first constituent element at the first temperature is equal to that of the second constituent element. The partial pressure of the raw material gas containing the first constituent element is higher than the saturation vapor pressure of the constituent element, and the partial pressure of the raw material gas containing the first constituent element is smaller than the partial pressure of the raw material gas containing the second constituent element. Preferably, it is higher than the pressure.

When the semiconductor layer is heated while maintaining the semiconductor layer grown at a growth pressure of 1 atm or more at a low pressure of 1 atm or less, at least one of the elements constituting the semiconductor layer is substantially removed from the semiconductor layer. Preferably, the substrate is heated at a temperature equal to or higher than a decomposition temperature at which the semiconductor layer starts to decompose.

In the method for growing a semiconductor multi-layer crystal according to the present invention, a plurality of first source gases containing an element constituting the first semiconductor layer, at least one of which is an organometallic compound, may be used. Introducing the first source gas into the growth chamber; and maintaining the pressure in the growth chamber at a first growth pressure of at least 1 atm near the surface of the substrate heated to the first temperature. Decomposing the raw material gas to epitaxially grow the first semiconductor layer on the substrate, and maintaining the pressure in the growth chamber at the first growth pressure during the epitaxial growth of the first semiconductor layer. Lowering the temperature of the substrate to a second temperature lower than the first temperature, and thereafter changing the pressure of the growth chamber to a second growth pressure of 1 atm or less; Multiple elements containing constituent elements Introducing a plurality of second source gases, at least one of which is an organometallic compound, into the growth chamber, and maintaining the pressure in the growth chamber at the second growth pressure. Decomposing the source gas in the vicinity of the surface of the first semiconductor layer of the substrate heated to the second temperature, thereby epitaxially growing the second semiconductor layer on the first semiconductor layer And a plurality of third semiconductor elements including the element constituting the third semiconductor layer.
Introducing a plurality of third source gases, at least one of which is an organometallic compound, into the growth chamber, and maintaining the pressure in the growth chamber at the second growth pressure. Increasing the temperature of the substrate to a second temperature higher than the second temperature, and thereafter changing the pressure of the growth chamber to a third growth pressure of 1 atm or more; The source gas is decomposed in the vicinity of the surface of the second semiconductor layer of the substrate heated to the third temperature while maintaining the third growth pressure, whereby the second semiconductor layer is formed on the second semiconductor layer. Epitaxially growing the third semiconductor layer, thereby achieving the above object.

The first and third semiconductor layers are made of ZnMgS
And the second semiconductor layer is made of ZnSe and Zn.
It may have a superlattice structure of CdSe.

[0026]

When the semiconductor layer is grown, the growth pressure is increased to 1 atm or more. If necessary, a source gas containing an element having a high saturated vapor pressure among the constituent elements of the semiconductor layer is converted to a saturated vapor pressure. The source gas is supplied so as to be present in excess of the source gas containing a low element. Thus, even when the semiconductor layer is grown at a high temperature at which the quality of the crystal is improved, an element having a high saturated vapor pressure can be grown almost stoichiometrically on the substrate, and constituent elements are separated from the grown semiconductor layer. Nothing. Accordingly, a semiconductor layer having high quality crystallinity can be obtained.

In the case of laminating a large number of thin films, if it is necessary to optimize the growth conditions of each layer, each thin film is grown at an optimum pressure while changing the pressure, so that each good thin film can be obtained. . In order to improve the steepness of the composition between the layers of the compound semiconductor, the reaction chamber is evacuated before the next semiconductor layer is crystal-grown, and the carrier gas including the constituent elements is rapidly switched. Steepness can be improved by using a separate growth chamber for each layer of the semiconductor multilayer.

[0028]

【Example】

(Embodiment 1) A method for growing a crystal of a semiconductor layer according to the present invention will be described with reference to FIG.

First, the semiconductor growth apparatus 10 used in the present invention
The outline of No. 1 will be described. The semiconductor growth apparatus 101 has a growth chamber 1 made of stainless steel, and a susceptor 2 of a resistance heating type is provided in the growth chamber 1. The growth chamber 1 has a structure that can withstand a high pressure, and preferably has a structure that can withstand a high pressure of about 10 atm. The susceptor 2 is provided with a rotation control system 21 so that the susceptor 2 can rotate as needed.
The susceptor 2 can be heated up to 900 ° C. by a resistance heating method. The growth chamber 1 is provided with a pressure gauge 16 for measuring the pressure of the atmosphere 4 in the growth chamber 1. A substrate 3 on which a semiconductor layer is formed is set on the susceptor 2.

The growth chamber 1 is connected to an exhaust pump 20 via a block valve 19, and the atmosphere 4 in the growth chamber 1 is
Exhaust. The exhausted gas is discharged to the atmosphere through the abatement device 23. The block valve 19 has a flow controller 1
7 is connected, and can be released to the atmosphere via the flow controller 17 and the abatement device 22 by switching by the block valve 19.

In order to supply a source gas containing an element constituting the semiconductor layer, a DMZn (dimethyl zinc) cylinder 6, a DMSe (dimethyl selenium) cylinder 7, a DMS (dimethyl sulfa) cylinder 8, and a Cp ₂ Mg (cyclopentane) cylinder are provided. A dienyl magnesium) cylinder 9 is used in this embodiment. These source gases are filled in the cylinders 6 to 9 together with hydrogen. Since hydrogen gas is used as a carrier gas, a hydrogen cylinder 5 is also used. These cylinders 5
9 are connected to the block valve 18 via flow controllers 10 to 14, respectively. The block valve 18 is further connected to the growth chamber 1 via the flow controller 15. The flow controllers 10 to 15 and the block valve 18 correspond to the maximum filling pressure of each of the cylinders 5 to 9. For example, the hydrogen cylinder 5 is filled at a pressure of 50 kg / cm ² , and the other cylinders 6 to 9 are filled at a pressure of several tens kg / cm ² .

Each of the flow controllers 10 to 15 and 17, the block valves 18 and 19, and the exhaust pump 20
Is controlled by a computer so that the pressure in the growth chamber 1 can be maintained at an arbitrary value based on the pressure detected by the pressure gauge 16. Specifically, the partial pressure ratios of the source gases are controlled by the flow controllers 11 to 14, the concentrations of these source gases are controlled by the flow controller 10, and the growth pressure is controlled by the flow controller 15.
When a mixed crystal such as Zn _1-x Mg _x S _y Se _1-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is prepared, the DMZn cylinder 6 and the DMS
e cylinder 7, DMS cylinder 8, and Cp ₂ Mg cylinder 9
Is introduced into the growth chamber 1 via the block valve 18 by controlling the respective flow controllers 11 to 14. Growth room 1
When the atmosphere 4 is kept at 1 atm or more, the exhaust pump 20
Therefore, there is no need to exhaust the inside of the growth chamber 1. The pressure of the atmosphere 4 is controlled by the flow controller 17 and can be discharged from the abatement apparatus 22 to the atmosphere by a difference from the atmospheric pressure. On the other hand, the gas in the growth chamber 1 can be quickly switched by switching the block valve 19 and evacuating the growth chamber 1 by the exhaust pump 20.

In order to improve the uniformity of the thickness, electrical characteristics (eg, carrier concentration, mobility, etc.) and optical characteristics (eg, photoluminescence intensity, emission wavelength, etc.) of the grown semiconductor layer, a rotation control system 21 is required. It is preferable that the susceptor 2 be rotated at a high speed (for example, 1000 rpm) to reduce the thickness of the boundary layer on the substrate 3. Thus, the efficiency with which the constituent elements are incorporated into the semiconductor layer can be increased. Further, the influence of heat convection can be prevented. In particular, it is effective for the growth of a semiconductor containing a constituent element having a high saturated vapor pressure. Further, the substrate 3 may be rotated at a low speed.

Referring to FIG. 1 below, Zn _0.9 Mg
A method for growing a semiconductor layer made of _0.1 S _0.1 Se _0.9 will be described.

On the susceptor 2 in the growth chamber 1, a GaAs substrate 3 is set as a substrate. Then, a hydrogen gas is introduced from the hydrogen cylinder 5 into the growth chamber 1, and the pressure in the growth chamber 1 is maintained at a growth pressure of 5 kg / cm ² . The pressure in the growth chamber 1 is a pressure gauge 1
Measured at 6. Based on the value detected by the pressure gauge 16,
The flow controller 17 is automatically controlled to maintain a constant growth pressure.

Next, the susceptor 2 is heated so that the temperature of the GaAs substrate 3 is maintained at 500.degree. Then, by controlling the flow rate of each of the cylinders 6 to 9 by the flow controllers 11 to 14, the source gas flows from each of the cylinders 6 to 9 so that the ratio of the constituent elements is equal to the composition ratio of the semiconductor layer to be grown. The mixed source gas flows into the growth chamber 1 via the flow controller 15. The pressure of the growth chamber 1 is 1 to 10k
flow control meter 15, 17 is adjusted so that g / cm ² degree preferably is maintained at about 2~5kg / cm ^2. Gas from the growth chamber is exhausted to the detoxification device 22 via the block valve 19 and the flow controller 17. Depending on the growth conditions, the crystal may be grown while rotating the substrate 3 by the control system 21.

Since only the GaAs substrate 3 is heated in the growth chamber 1, the source gases flowing into the growth chamber 1 reach the surface of the GaAs substrate 3 without being decomposed or reacted with each other. Then, near the surface of the GaAs substrate 3, each source gas is decomposed by heat radiated from the GaAs substrate 3, and a semiconductor layer having a composition of Zn _0.9 Mg _0.1 S _0.1 Se _0.9 is epitaxially grown on the GaAs substrate 3.

Usually, Zn _0.9 Mg under a low pressure of 1 atm or less.
_When a semiconductor layer having a composition of _0.1 S _0.1 Se _0.9 is heated to 500 ° C., sulfur and selenium are desorbed. However, according to the method of the present invention, since the pressure in the reaction chamber 1 is high, sulfur and selenium are hardly desorbed from the grown semiconductor layer. Therefore, high quality Zn
_{A 0.9} Mg _0.1 S _0.1 Se _0.9 semiconductor crystal is formed on the GaAs substrate 3.

On the GaAs substrate 1, Z having a desired thickness
n _0.9 Mg _0.1 after growing the semiconductor layer of S _0.1 Se _0.9,
The supply of the source gas from the cylinders 6 to 9 is stopped. A vent line (not shown) may be provided between the block valve 18 and the growth chamber 1 so that the source gas does not enter the growth chamber 1. The only gas that enters the growth chamber 1 is hydrogen gas, and the temperature in the growth chamber 1 is reduced while replacing the atmosphere in the growth chamber 1 with hydrogen, and the pressure is returned to the atmospheric pressure. To set the pressure to atmospheric pressure, the gas from the growth chamber 1 is switched to the vacuum pump 20 by the block valve 19 and exhausted.

Thus, a mixed crystal semiconductor made of ZnMgSSe can be grown on the GaAs substrate 3 under high pressure. As described above, even if the growth temperature is increased, atoms do not escape from the mixed crystal, so that a crystal having extremely excellent quality can be grown as compared with the conventional low-temperature crystal growth at a low temperature.

A semiconductor layer made of ZnSe or ZnS can be grown by the same procedure. In particular, in the case where the semiconductor layer is not a mixed crystal semiconductor, an atmosphere in which an element having a high saturated vapor pressure among elements constituting the semiconductor layer is excessive can be used. When the saturated vapor pressures of zinc and sulfur or zinc and selenium at a growth temperature of 500 ° C. are compared, the saturated vapor pressures of sulfur and selenium are each approximately 5 times smaller than that of zinc.
Orders of magnitude and about two orders of magnitude higher. Therefore, DMS containing sulfur and selenium
The gas flow rate of DMSe or DMSe is set to be much larger than the gas flow rate of DMZn containing zinc, and DMS constituting the growth pressure
And the partial pressure of DMSe may be higher than the partial pressure of DMZn. By such a method, desorption of sulfur and selenium is further suppressed, and a semiconductor layer having higher quality can be obtained.

Undoped ZnS obtained by the embodiment
The semiconductor layer e has good characteristics having a carrier concentration of 1 × 10 ¹⁵ cm ⁻³ or less and a mobility of 400 cm ² / Vsec or more. When doping is required, for example, nitrogen in a plasma state may be used for p-type conversion, and chloride (for example, ZnCl ₂ ) may be used for n-type conversion. The growth rate depends on the growth pressure, the growth temperature, and the substrate rotation speed, but is about 1 μm / h under the conditions of the present embodiment.
r. Increase the growth rate to several tens in a relatively short time.
It is also possible to produce a semiconductor layer having a thickness of at least μm.

Lattice matching to GaAs (misfit is 1 ×
^10-4 or less), ZnSS having a thickness of about 200 μm
By preparing a semiconductor layer of e and removing the GaAs substrate, a high-quality ZnSSe substrate can be obtained. Conventionally, a substrate having a large diameter of the II-VI group could not be obtained. However, according to this method, a crystal growth rate can be increased, and thus a substrate having a large diameter can be manufactured as compared with the case of pulling. .

Embodiment 2 A method for forming a semiconductor structure used in a ZnSe-based laser diode will be described below with reference to FIGS.

The semiconductor growth apparatus 10 used in this embodiment
Reference numeral 2 is substantially the same as the semiconductor growth apparatus 101 described in the first embodiment, except that a source gas for supplying elements constituting a semiconductor is different. The semiconductor growth apparatus 102 includes a DMCd (dimethyl cadmium) cylinder 25 for supplying cadmium, a ZnCl ₂ cylinder 26 for supplying chlorine,
NH ₃ (ammonia) cylinder 2 for supplying nitrogen
7, and a flow controller 1 for controlling the flow rate of the raw material gas flowing from these cylinders 9 and 25 to 27.
4 and 28 to 30 are further provided.

As shown in FIG. 3, the semiconductor structure 103 formed in this embodiment includes an n-type cladding layer 35, an active layer 36 formed on the n-type cladding layer 35, and an active layer 36.
It has a p-type cladding layer 37 formed thereon. The n-type cladding layer 35 and the p-type cladding layer 37 are made of Zn _0.9 Mg.
It is formed from _0.1 S _0.1 Se _0.9 and is doped with chlorine and nitrogen, respectively. The active layer 36 is made of undoped ZnS
e (thickness: 10 nm) / undoped ZnCdSe (thickness: 50 nm) have a superlattice structure alternately stacked a plurality of times.

First, a GaAs substrate 3 is set as a substrate on the susceptor 2 in the growth chamber 1. Then, a hydrogen gas is introduced into the growth chamber 1 from the hydrogen cylinder 5, and the pressure in the growth chamber 1 is set to about 1 to 10 kg / cm ² , preferably 2 to 5 kg / cm ^2.
keep to the order of cm ^2. The pressure in the growth chamber 1 is measured by a pressure gauge 16. The flow controller 17 is automatically controlled based on the value detected by the pressure gauge 16, and is maintained at a constant growth pressure.

Next, the susceptor 2 is heated so that the temperature of the GaAs substrate 3 is maintained at 500.degree. The flow rates of the cylinders 6 to 9 and 26 are controlled by the flow controllers 11 to 14 and 28 to 30 so that the ratio of the constituent elements becomes equal to the composition ratio of the n-type cladding layer 35 to be grown. Gas flows from cylinders 6-9 and 26.
The mixed source gas is supplied to the growth chamber 1 via the flow controller 15.
Is poured into. The pressure in the growth chamber 1 is always 5 kg / cm ²
The flow controllers 15 and 17 are adjusted so as to be maintained at the same level. Gas from the growth chamber is exhausted to the detoxification device 22 via the block valve 19 and the flow controller 17. Example 1
As described above, the n-type cladding layer 35 having a desired composition ratio grows on the GaAs substrate 3.

In this embodiment, the growth conditions are controlled according to the timing described with reference to FIG. After growing the n-type cladding layer 35 until it has a predetermined thickness,
As shown in FIG. 4, first, the temperature of the GaAs substrate 3 is gradually lowered to 300 ° C. by adjusting the heating of the susceptor 2. When the temperature of the GaAs substrate 3 drops to 300 ° C.,
The inside of the growth chamber 1 is evacuated by the exhaust pump 20 so that the pressure in the growth chamber 1 decreases to 0.1 atm.

Next, the flow controllers 11, 12, and 28 are controlled to flow the source gases from the cylinders 6, 7, and 25 so that the ratio of the constituent elements is equal to the composition ratio of the active layer 36. By reducing the growth pressure from 5 atm to 0.1 atm, an active layer 36 having a superlattice structure is formed using the same method as the conventional reduced pressure MOVPE. Growth pressure 0.1
Since the pressure is reduced to about the atmospheric pressure, the atmosphere 4 can be changed instantaneously without the gas remaining in the growth chamber 1. Therefore, by switching the source gas, the gas in the growth chamber 1 can be instantaneously switched, and a superlattice structure having a steep interface can be formed. Since the temperature and pressure conditions for forming the active layer are switched during the growth of the n-type cladding layer 35, the temperature and pressure at the interface between the n-type cladding layer 35 and the active layer 36 where the composition of the semiconductor changes are changed. Lattice defects caused by the change hardly occur. This is due to changes in composition, temperature,
This is because the timing of the pressure change is shifted from the timing of the pressure change.

When the active layer 36 has a desired thickness, first, as shown in FIG.
The source gas flows from the cylinders 6 to 9 and 27 so that the ratio of the constituent elements is equal to the composition ratio of the p-type cladding layer 37 to be grown by controlling the flow rate of 7 by the flow controllers 11 to 14 and 30. Next, the pressure is increased to 5 atm, and then the susceptor 2 is heated so that the temperature of the GaAs substrate 3 becomes 500 ° C. Thereby, the p-type cladding layer 37 is similarly grown. The following procedure is the same as in the first embodiment.

According to the method of this embodiment, the n-type cladding layer 35 and the p-type cladding layer 37 are grown under a growth pressure of 1 atm or more. And lattice defects therein are extremely small. Further, since the active layer is grown under a growth pressure of 1 atm or less, the cut of the source gas is improved, and as a result, a superlattice structure having a steep interface can be formed. Further, the n-type cladding layer 35 on which the active layer is formed is formed.
Since the number of lattice defects in the inside is extremely small, the influence of the lattice defects on the active layer is extremely small, and the number of lattice defects in the active layer is also small. Furthermore, during the growth of the active layer which is easily affected by the fluctuation of the growth conditions, the growth conditions are kept constant.
Therefore, a laser diode with high luminous efficiency can be obtained by using the semiconductor structure formed by the method of this embodiment.

(Embodiment 3) A method for forming a semiconductor structure used for a GaN-based light emitting diode will be described below with reference to FIGS.

The semiconductor growth apparatus 104 used in this embodiment is substantially the same as the semiconductor growth apparatus 101 described in the first embodiment, except that the source gas for supplying the elements constituting the semiconductor and the carrier gas are different. TM for semiconductor growth apparatus 102 to supply N ₂ gas cylinder 41 supplies the N ₂ used as the carrier gas, TMG (trimethyl gallium) for supplying a gallium cylinder 42, indium
I (trimethyl indium) gas cylinder 43, the raw material gas and carrier flow aluminum TMA (trimethylaluminum) gas cylinder 44 for supplying, and NH ₃ (ammonia) gas cylinder 45 for supplying nitrogen, and from these cylinders 41 to 45 Further provided are flow controllers 46 to 50 for controlling the gas flow.

As shown in FIG. 6, the semiconductor structure 105 manufactured in the present embodiment has a non-single-crystal GaN layer 53, a GaN layer 54 formed on the non-single-crystal GaN layer 53, and a GaN layer 54 formed on the GaN layer 54. GaInN layer 55 and GaInN
It has a GaN layer 56 formed on the layer 55.

First, a substrate 51 made of 6H—SiC, which has been degreased and cleaned, is set on a susceptor 52 made of molybdenum.
Then, using a flow controller 46, nitrogen gas is introduced from the nitrogen cylinder 41 into the growth chamber 1 at a rate of 10 L / min.
The pressure in the growth chamber 1 is maintained at about 1 to 5 atm, preferably 2 atm. The pressure in the growth chamber 1 is measured by a pressure gauge 16. The flow controller 17 is automatically controlled based on the value detected by the pressure gauge 16, and is maintained at a constant growth pressure. Susceptor 5
2 is 80 to improve the uniformity of the semiconductor layer to be grown.
Rotate at a rate of 0 rpm.

The susceptor 2 is heated so that the temperature of the substrate 51 becomes 1200 ° C., and the surface of the substrate 51 is cleaned. Thereafter, the heating of the susceptor 2 is adjusted, and the temperature of the
Keep at 00 ° C. 5 L from NH ₃ cylinder 45 to growth chamber 1
ammonia gas at a rate of 1 minute, and after 1 minute, TMG
By flowing trimethylgallium from the cylinder 42 to the growth chamber 1 at a rate of 50 cc / min, the non-single-crystal GaN layer 53 is grown on the substrate 51. Non-single-crystal GaN layer 53
When the thickness reaches about 20 nm, the supply of ammonia gas and trimethylgallium is stopped.

Next, while maintaining the substrate 51 at about 1000 ° C., ammonia gas was flowed from the NH ₃ cylinder 45 into the growth chamber 1 at a rate of 5 L / min.
From above into growth chamber 1 at a rate of 100 cc / min. Thereby, G having a thickness of 3 μm
An aN layer 54 grows on the non-single-crystal GaN layer 53. Ga
Since the N layer 54 has a sufficient thickness, the influence of defects generated at the interface between the substrate 51 and the non-single-crystal GaN layer 53 is significantly reduced, and the surface of the GaN layer 54 becomes flat.

Next, while maintaining the substrate 51 at about 800 ° C., ammonia gas is flowed from the NH ₃ cylinder 45 into the growth chamber 1 at a rate of 10 L / min, and at the same time, the TMG cylinder 42
And 50 cc each from TMI cylinder 43 to growth chamber 1
/ Min and 400 cc / min of trimethylgallium and trimethylindium. This allows
The GaInN layer 55 having a thickness of 5 nm is
Grow on top.

Thereafter, the supply of trimethylindium was stopped, and the GaN layer 56 having a thickness of 1 μm was replaced with GaInN.
After the growth on the layer 55, the supply of trimethylgallium is stopped. The temperature of the substrate 51 is gradually lowered to 300 ° C.
When the temperature of the substrate 51 drops below, the supply of ammonia is stopped.

The semiconductor structure 105 obtained according to this embodiment
The surface of the GaN layer 56, which is the uppermost layer, is mirror-like. Also, by PL emission from the GaInN layer 55,
The InN composition in the GaInN layer 55 is estimated to be 0.3.

On the other hand, when a semiconductor structure similar to the semiconductor structure 105 is manufactured at a growth pressure of about 0.1 atm according to a conventional method, the surface of the obtained semiconductor structure has irregularities. According to the TEM observation, it can be seen that this is due to the poor crystal quality of the GaInN layer. Further, the InN composition in the GaInN layer is estimated to be 0.08.

According to the present invention, by growing the semiconductor layer under high pressure, the decomposition efficiency of ammonia is improved, so that the GaInN layer is sufficiently loaded with nitrogen and the GaI
Nitrogen vacancies in the nN layer are reduced. As a result, a GaInN layer having high quality crystallinity is formed, and GaN / G
It is considered that the crystallinity of the whole semiconductor multilayer composed of aInN / GaN is improved.

(Embodiment 4) In this embodiment, a method of instantaneously switching the source gas staying in the growth chamber will be described.

FIG. 7A schematically shows a semiconductor growth apparatus 106 used in the method described in this embodiment. In the semiconductor growth apparatus 106, the same components as those of the semiconductor growth apparatus 101 shown in FIG. 1 are denoted by the same reference numerals.

The semiconductor growth apparatus 105 has a growth chamber 61. The growth chamber 61 is made of a high pressure-resistant stainless steel that can withstand several tens of kg / cm 2, and includes a main part 62 through which a source gas flows and a substrate holding part 63 for accommodating a susceptor 64 as shown in FIG. . When the susceptor 64 holds the substrate 3 on its surface, the susceptor 64 and the main portion 62
Are housed in the substrate holding part 63 so that the bottom part 66 is located at substantially the same height as the bottom part 66. The cross-sectional area 65 of the main part 62 is extremely small. In particular, it is preferable that the distance between the upper surface 67 and the bottom surface 66 of the main portion 62 be as small as possible so that the space above the surface of the substrate 3 is narrowed. Although it depends on the semiconductor material to be grown, it is preferably about 1 cm. Also, the width of the main portion 62 is preferably about the diameter of the susceptor 64.

As described above, by reducing the cross-sectional area of the portion where the gas flows in the growth chamber 61, the flow rate of the gas flowing into the reaction chamber 61 via the flow controller 15 can be increased. Therefore, the boundary layer (flow of gas contributing to crystal growth) formed above the substrate 3 becomes thin, and the growth rate of the semiconductor layer increases. This is particularly effective when growing a constituent element having a high saturated vapor pressure. Further, by increasing the flow velocity, the switching of the atmosphere in the growth chamber 61 can be accelerated.

When the temperature of the growth chamber 61 rises due to heat radiation generated by heating the susceptor 64, the cooling system 68 may be provided with the growth chamber 61 on the inner wall or the like. If the substrate needs to revolve on its own due to crystal growth, it is appropriately performed using the control system 21.

When the components of the gas in the atmosphere 4 of the growth chamber 61 are to be switched more steeply, the inside of the reaction chamber 61 is evacuated by switching the block valve 19 to the vacuum exhaust pump 20 system.

Semiconductor growth apparatus 1 shown in Examples 1 to 3
By using the semiconductor growth apparatus 106 of this embodiment instead of 01, 102, and 104, the growth rate of the semiconductor layer shown in each embodiment can be increased.

Further, the semiconductor growth apparatus 106 having the above structure can be developed into a multi-chamber type semiconductor growth apparatus. Using a semiconductor growth apparatus having a high-pressure growth chamber and a low-pressure growth chamber, a semiconductor layer is grown under a high-pressure condition of 1 atm or more in the high-pressure growth chamber, and a conductor layer is grown under a low-pressure condition of 1 atm or less in the low-pressure growth chamber If the group is grown, the semiconductor structure shown in the second embodiment can be formed more easily.

[0072]

According to the present invention, it has been considered that it is difficult to obtain a high-quality crystal, especially ZnSe, ZnS, ZnMgSSe, ZnCdSSe, and the like.
II-VI compound semiconductors such as ZnMnSSe, Cu
GaSe ₂ , CuAlSe ₂ , CuAlS ₂ , CuGaS ₂
Chalcopyrite-based semiconductor such as GaN, G
A semiconductor layer such as aInN or AlGaInN can be obtained. In particular, it is suitable for growing a semiconductor layer containing an element having a high saturated vapor pressure such as selenium or sulfur, and is an indispensable crystal growth method for manufacturing optoelectronic materials.

[Brief description of the drawings]

FIG. 1 shows an outline of a MOVPE apparatus used for a method of growing a semiconductor layer according to a first embodiment of the present invention.

FIG. 2 schematically shows an MOVPE apparatus used for a method of growing a semiconductor layer according to a second embodiment of the present invention.

FIG. 3 shows a semiconductor structure formed according to a second embodiment.

FIG. 4 is a graph showing timing for operating the device shown in FIG. 2;

FIG. 5 schematically shows an MOVPE apparatus used for a method for growing a semiconductor layer according to a third embodiment of the present invention.

FIG. 6 shows a semiconductor structure formed according to a third embodiment.

FIG. 7A schematically shows an MOVPE apparatus used for a method of growing a semiconductor layer according to a third embodiment of the present invention, and FIG. 7B is a perspective view of a main part. ing.

[Explanation of symbols]

1 growth chamber 2 susceptor 3 substrate 4 growth chamber atmosphere 5 H2 cylinder 6 DMZn cylinder 7 DMSe cylinder 8 DMS cylinder 9 Cp ₂ Mg gas cylinder 10～15,17 flow control meter 16 pressure gauge 18, 19 block valve 20 exhaust pump 21 speed control System 22, 23 Removal equipment 101 Semiconductor growth equipment

Claims (10)

(57) [Claims] 1. A plurality of first source gases containing an element constituting a first semiconductor layer, of which at least one is an organometallic compound, is introduced into a growth chamber. Decomposing the first source gas in the vicinity of the surface of the substrate heated to a first temperature while maintaining the pressure of the growth chamber at the first growth pressure, so that the first A step of epitaxially growing one semiconductor layer; and a plurality of second source gases containing an element constituting the second semiconductor layer, at least one of which is an organometallic compound. Introducing the pressure into the growth chamber; and maintaining the pressure in the growth chamber at a second growth pressure while maintaining a second growth pressure.
By decomposing the second source gas in the vicinity of the surface of the substrate heated to a temperature first semiconductor layer of epitaxially growing a semiconductor layer of the second to the first semiconductor layer, encompasses, at least one of the growth pressure and the second growth pressure of the first at least 1 atm, the crystal growth method of the semiconductor multilayer. 2. The growth chamber includes a first sub-growth chamber and a second sub-growth chamber, wherein the first semiconductor layer is grown in the first sub-growth chamber, and wherein the second semiconductor layer is grown in the first sub-growth chamber. The method for growing a semiconductor multilayer crystal according to claim 1, wherein is grown in the second sub-growth chamber . Wherein one of the first growth pressure and the second growth pressure is at least 1 atm, the other is less than 1 atm, the semiconductor multilayer crystal growth method according to claim 1. 4. The semiconductor layer grown at a growth pressure of 1 atm or more is composed of at least first and second constituent elements, and the saturated vapor pressure of the first constituent element at the first temperature is equal to the saturated vapor pressure of the first constituent element. The partial pressure of the raw material gas containing the first constituent element is higher than the saturated vapor pressure of the constituent gas of the second constituent element. 2. The method for growing a semiconductor multilayer crystal according to claim 1 , wherein said partial pressure is higher than said partial pressure. 5. When heating the semiconductor layer while maintaining the semiconductor layer grown at a growth pressure of 1 atm or more at a low pressure of 1 atm or less, at least one of the elements constituting the semiconductor layer is removed from the semiconductor layer. substantially eliminated by the semiconductor layer is to heat the substrate at a decomposition temperature or higher temperatures to start degradation, semiconductor multilayer crystal growth method according to claim 1. 6. The crystal growth of a semiconductor multilayer according to claim 1 , wherein said semiconductor layer includes one of a II-VI compound semiconductor, a III-V semiconductor, and a chalcopyrite-based semiconductor. Method. 7. The method according to claim 6 , wherein one of the constituent elements includes at least one of selenium and sulfur. 8. The method according to claim 6 , wherein the constituent element includes nitrogen. 9. A plurality of first source gases containing an element constituting the first semiconductor layer, of which at least one is an organometallic compound, is introduced into the growth chamber. Decomposing the first source gas in the vicinity of the surface of the substrate heated to a first temperature while maintaining the pressure in the growth chamber at a first growth pressure of 1 atm or more. A step of epitaxially growing the first semiconductor layer thereon; and a step of lowering the second temperature lower than the first temperature while maintaining the pressure of the growth chamber at the first growth pressure during the epitaxial growth of the first semiconductor layer. Lowering the temperature of the substrate to a temperature equal to or lower than the temperature of the substrate, and then changing the pressure of the growth chamber to a second growth pressure of 1 atm or less; and a plurality of second raw materials containing an element constituting the second semiconductor layer. Gas, at least one of which A step of introducing a plurality of second source gases of an organometallic compound into the growth chamber; and a substrate heated to the second temperature while maintaining the pressure in the growth chamber at the second growth pressure. by decomposing the second source gas in the vicinity of the surface of the first semiconductor layer of epitaxially growing a semiconductor layer of a second on the first semiconductor layer, a third semiconductor layer structure Introducing a plurality of third source gases containing at least one kind of an organometallic compound into the growth chamber, the method comprising: From the second growth pressure to 1 atm or more
3, and then the pressure in the growth chamber is increased.
While maintaining the growth pressure of the third, the step of increasing the temperature of the higher third temperature to the substrate than the temperature of the second, while maintaining the pressure in said growth chamber to the growth pressure of the third, by decomposing the third source gas in the vicinity of the surface of the third second semiconductor layer of a substrate heated to a temperature of, epitaxially growing a semiconductor layer of the third on the second semiconductor layer And a method for growing a semiconductor multilayer crystal. 10. The first and third semiconductor layers are made of ZnM.
10. The method according to claim 9 , wherein the second semiconductor layer is made of gSSe, and the second semiconductor layer is made of a ZnSe and ZnCdSe superlattice structure.