JP2006351993A - Compound semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound semiconductor wafer where the p-type carrier density of an Al<SB>x</SB>Ga<SB>1-x</SB>As(0≤x<1) layer is created uniformly within a surface with good controllability. <P>SOLUTION: Material gas supplied into a reactor is decomposed thermally near a heated GaAs substrate 1, and an AlGaAs layer 2 grows on the substrate 1. As the material gas, TMA is used for an Al material, the mixed gas of TEG and TMG is used for a Ga material, and arsine is used for an arsenic material. By mixing and supplying TMG and TEG, the exchange reaction of a methyl group of TMA of the Al material and an ethyl group of TEG of the Ga material occurs. By the exchange reaction, the rate of the methyl group to be combined with Al is reduced, so that a probability is reduced in the take-in of the carbon of the methyl group combined with Al, so that the p-type carrier density of an AlGaAs layer is reduced. Consequently, the p-type carrier density can be controlled by adjusting the ratio of TMG and TEG of the Ga material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a compound semiconductor wafer having an _{Al x Ga 1-x As (} 0 ≦ x <1) layer on a GaAs substrate, is grown in particular controlling the carrier concentration of the _Al x _{Ga 1-x} As layer It relates to a compound semiconductor wafer.

  The laminated structure of compound semiconductor epitaxial crystals such as GaAs, InGaP, AlGaAs, and AlGaInP includes electronic devices such as FETs (field effect transistors), HEMTs (high electron mobility transistors), HBTs (heterojunction bipolar transistors), LEDs, lasers, etc. Widely used as a light emitting device. In general, these compound semiconductor electron / light-emitting devices are generally obtained by sequentially depositing a compound semiconductor crystal having a desired composition and thickness on a substrate such as GaAs by using a crystal growth method such as a metal organic chemical vapor deposition method (MOVPE method). Epitaxially grow.

  In the MOVPE method, a group III organometallic source gas and a group V source gas are introduced into a reaction furnace as a mixed gas of high-purity hydrogen carrier gas, and the source material is pyrolyzed near the substrate heated in the reaction furnace. A compound semiconductor crystal grows epitaxially on the substrate. Conventionally, when a p-type AlGaAs layer or the like is grown by the MOVPE method, a method of intentionally doping a p-type dopant and a method of adjusting the flow rate of arsine are used.

When AlGaAs is grown by the MOVPE method using trimethylgallium (TMG) as a Ga raw material, trimethylaluminum (TMA) as an Al raw material, and arsine as an As raw material, the bonding strength between Al atoms and carbon atoms is strong. As a result, in the epitaxial growth process of AlGaAs, TMA is not completely decomposed, and a methyl group containing carbon atoms is taken into the crystal in a state of being bonded to Al atoms. (For example, refer to Patent Document 1).
JP-A-4-326724.

However, the conventional p-type dopant doping method uses a bromo-based compound or a chromium-based compound as a doping raw material, but there are problems such as increased etching effect and memory effect due to side reactions and the like. Is difficult. In addition, it is difficult to control the carrier concentration of 1 × 10 ¹⁸ (cm ⁻³ ) or less.

  In addition, in the method of adjusting the arsine flow rate, it is difficult to finely adjust the carrier concentration, and since there is a large variation in the carrier concentration within the wafer surface, it is difficult to stably and reliably control the growth of the carrier concentration. . Further, when the AlGaAs layer is grown under a condition where the arsine flow rate is low, unnecessary impurities such as oxygen are mixed in, causing problems such as carrier killer.

The present invention solves the above-described problems and provides a compound semiconductor wafer in which the p-type carrier concentration of the Al _x Ga _1-x As (0 ≦ x <1) layer is controlled and uniform in the surface. is there.

In the first invention, a group III material and a V material are supplied on a semi-insulating GaAs substrate, and an epitaxial layer having an Al _x Ga _1-x As (0 ≦ x <1) layer using a metal organic chemical vapor deposition method. In the compound semiconductor wafer in which a layer is grown, a plurality of Group III materials having the same metal atoms and different organic groups bonded to each other are used as the Group III materials, and the supply ratio thereof is adjusted to adjust the Al _x Ga. _The compound semiconductor wafer is characterized by being grown while controlling the carrier concentration of the _1-x As layer.

When a plurality of Group III raw materials having different organic groups such as hydrocarbon groups (alkyl groups, etc.) bonded with the same metal atom are supplied, an exchange reaction of different organic groups occurs, and each organic group bonded to Al or Ga And the quantity of organic groups containing carbon incorporated into the Al _x Ga _1-x As layer changes. Therefore, the p-type carrier concentration of the Al _x Ga _1-x As layer can be controlled by adjusting the supply ratio of the plurality of group III raw materials having the same metal atoms and different organic groups bonded thereto.

  The compound semiconductor wafer (epitaxial wafer) of the present invention is used for electronic devices such as FETs (field effect transistors), HEMTs (high electron mobility transistors), HBTs (heterojunction bipolar transistors), and light emitting devices such as semiconductor lasers. . The AlGaAs layer is used for a buffer layer or a Schottky layer that can realize good device characteristics.

  According to a second invention, in the first invention, the plurality of Group III materials having the same metal atoms and different organic groups bonded thereto are triethylgallium (TEG) and trimethylgallium (TMG) as gallium materials. A compound semiconductor wafer is characterized in that trimethylaluminum (TMA) and triethylaluminum (TEA) are used as aluminum raw materials.

A third invention is a compound semiconductor wafer according to the first or second invention, wherein the carrier concentration is 1 × 10 ¹⁸ cm ⁻³ or less.

Arsine is often used as an arsenic raw material. However, when the carrier concentration is controlled to 1 × 10 ¹⁸ cm ⁻³ or more, it is necessary to extremely reduce the supply amount of arsine, which causes deterioration of the surface state of the epitaxial layer. Since the amount of impurities other than carbon and carbon increases, the carrier concentration is preferably 1 × 10 ¹⁸ cm ⁻³ or less.

A fourth invention is a compound semiconductor wafer characterized in that arsine (AsH ₃ ) is used as an arsenic material in the first to third inventions.

According to a fifth aspect of the invention, there is provided the compound semiconductor wafer according to any one of the first to third aspects, wherein the arsenic raw material is a mixture of arsine (AsH ₃ ) and trimethylarsine (As (CH ₃ ) ₃ ). It is.

According to the present invention, a compound semiconductor wafer having an Al _x Ga _1-x As (0 ≦ x <1) layer that is well controlled to a desired p-type carrier concentration and has a uniform in-plane distribution of the p-type carrier concentration. Is obtained.

Hereinafter, an embodiment of a compound semiconductor wafer according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing the structure of a compound semiconductor wafer according to an embodiment, in which an AlGaAs layer 2 is grown on a semi-insulating GaAs substrate 1 by the MOVPE method. This wafer is manufactured for the purpose of measuring the carrier concentration of the AlGaAs layer 2 and the compound semiconductor wafer used in an actual device uses the AlGaAs layer as a buffer layer, a Schottky layer, etc. Usually, another semiconductor layer is formed on the layer 2 or between the AlGaAs layer 2 and the GaAs substrate 1. In some cases, the AlGaAs layer is the uppermost layer.

  A method for manufacturing the wafer by the MOVPE method will be briefly described. A GaAs substrate 1 on which an epitaxial layer is grown is set on a susceptor (not shown), and a source gas and a dilution gas are supplied into the reaction furnace while the GaAs substrate 1 is heated in the reaction furnace. The supplied source gas is decomposed by heat, and an epitaxial layer (AlGaAs layer 2) is formed on the substrate 1. As source gases, TMA was supplied as an Al source, a mixed gas of TEG and TMG as a Ga source, arsine as an arsenic source, and hydrogen as a dilution gas.

  By mixing and supplying TMG and TEG as Ga raw materials, the methyl group of TMG and the ethyl group of TEG cause an exchange reaction. This exchange reaction also occurs between the methyl group of TMA, which is an Al raw material, and the ethyl group of TEG, which is a Ga raw material. Therefore, by supplying two types of Ga raw materials, TMG and TEG, some methyl groups of TMA cause an exchange reaction, and the methyl group and ethyl group are bonded to Al atoms. As a result of this exchange reaction, the proportion of methyl groups bonded to Al (the bonding force with Al is large and easily incorporated into the growth crystal) decreases, and when Al contributes to growth, the methyl groups bonded to Al The probability of carbon incorporation is reduced, and the p-type carrier concentration of the AlGaAs layer is reduced.

  This means that the p-type carrier concentration can be controlled by adjusting the distribution / ratio of TMG and TEG of the Ga raw material. Similarly, when TEA is used as the Al raw material and TEG and TMG are used as the Ga raw material, an exchange reaction occurs between the ethyl group of TEA and the methyl group of TMG, thereby distributing the TMG and TEG of the Ga raw material. -The p-type carrier concentration can be controlled by adjusting the ratio. Furthermore, when TMA and TEA are used as the Al raw material, TEG or TMG is used as the Ga raw material, and when TMA and TEA are used as the Al raw material and TEG and TMG are used as the Ga raw material, the same effect can be obtained. It is done.

  In addition, as described above, it is reliable and easy that the AlGaAs layer can be grown by using commonly used raw materials (TMG, TEG, TMA, TEA, arsine) and controlling the p-type carrier concentration. It can be implemented in a very useful manner.

In order to confirm that the p-type carrier concentration of the AlGaAs layer can be controlled by adjusting the ratio of TMG and TEG of the Ga raw material described above, the ratio of TEG and TMG is changed, and the group V / III ratio is 50 Then, an AlGaAs layer having an Al composition ratio of 50% was grown on the GaAs substrate under the conditions of 100 and 100. FIG. 2 shows the result of measuring the carrier concentration of the fabricated wafer using CV measurement. As shown in FIG. 2, it can be seen that by changing the ratio of TMG and TEG, the carrier concentration can be satisfactorily controlled to a desired value in a range of about 1 × 10 ¹⁶ to 1 × 10 ¹⁸ (cm ⁻³ ). It has also been found that the incorporation of impurities such as oxygen can be reduced by supplying TEG.

  Furthermore, in order to confirm the uniformity of the in-plane distribution of the carrier concentration for the AlGaAs layer grown by the mixed supply of TMG and TEG, an AlGaAs layer having an Al composition ratio of 30% is grown on a 6-inch GaAs substrate. It was. For comparison, a wafer on which an AlGaAs layer having an Al composition ratio of 30% was grown by adjusting the arsine flow rate without doping impurities was also produced. For these wafers, the carrier concentration was measured at a pitch of 5 mm in the direction perpendicular to the orientation flat using CV measurement. The result is shown in FIG. As shown in the figure, the in-plane distribution of carrier concentration is uniform in the AlGaAs layer grown by the mixed supply of TMG and TEG of this embodiment.

  In the above embodiment, the present invention is applied to the growth of the AlGaAs layer. However, the present invention may be applied to the case where the GaAs layer (Al composition ratio x = 0) is grown. In this case, for example, TMG and TEG are used as the Ga raw material, and arsine and trimethylarsine are used as the arsenic raw material, and the ratio of these may be adjusted to control the p-type carrier concentration of the GaAs layer. If an arsenic raw material with trimethylarsine added to a predetermined ratio is used, the decomposition temperature range of trimethylarsine also becomes the temperature range in which methyl group and ethyl group can be exchanged, and the control range of p-type carrier concentration is limited. Will spread.

It is sectional drawing which shows the structure of the compound semiconductor wafer in one Embodiment of this invention. It is a figure which shows the relationship between the supply ratio of TEG and TMG, and the carrier concentration of an AlGaAs layer in one Embodiment of this invention. It is a figure which compares and compares the in-plane distribution of the carrier concentration of the AlGaAs layer in one Embodiment of this invention, and the in-plane distribution of the carrier concentration of the AlGaAs layer in the conventional compound semiconductor wafer.

Explanation of symbols

1 GaAs substrate 2 AlGaAs layer

Claims (5)

III group material on a semi-insulating GaAs substrate, supplying a V raw material, a compound of the epitaxial layer is grown having a _{Al x Ga 1-x As (} 0 ≦ x <1) layer using a metal organic chemical vapor deposition In semiconductor wafers
A plurality of Group III materials having the same metal atoms and different organic groups bonded to each other are used as the Group III materials, and the carrier concentration of the Al _x Ga _1-x As layer is controlled by adjusting their supply ratio. Compound semiconductor wafer characterized by being grown as a result.   In the compound semiconductor wafer according to claim 1, the plurality of group III raw materials having the same metal atoms and different organic groups bonded thereto are triethyl gallium and trimethyl gallium as the gallium raw materials, and as the aluminum raw materials, A compound semiconductor wafer comprising trimethylaluminum and triethylaluminum. 3. The compound semiconductor wafer according to claim 1, wherein the carrier concentration is 1 × 10 ¹⁸ cm ⁻³ or less.   4. The compound semiconductor wafer according to claim 1, wherein arsine is used as an arsenic material.   4. The compound semiconductor wafer according to claim 1, wherein a mixture of arsine and trimethylarsine is used as an arsenic raw material.

Images