JP2007042936A - Group iii-v compound semiconductor epitaxial wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a group III-V compound semiconductor epitaxial wafer which is capable of improving a device in insulation properties by improving a buffer layer and reducing a leakage current when the device is in operation. <P>SOLUTION: A buffer layer 11, a channel layer 14, spacer layers 13, and 15, carrier supply layers 12 and 16, and a contact layer 18, are epitaxially grown on a semi-insulating compound semiconductor substrate 10 for the formation of a group III-V compound semiconductor. A p-layer 22 and an n-layer 23 are formed in the buffer layer 11, using an n-GaAs layer, a p-GaAs layer, or an n-Al<SB>x</SB>Ga<SB>(1-x)</SB>As layer, a p-Al<SB>x</SB>Ga<SB>(1-x)</SB>As layer which have each a carrier concentration of ≤1E 17 cm<SP>-3</SP>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a metal-organic vapor phase epitaxy method, a molecular beam epitaxy method, a liquid phase epitaxy method in a III-V group compound semiconductor crystal used in an electronic device such as a field effect transistor (FET) or a high electron mobility transistor (HEMT). The present invention relates to a group III-V compound semiconductor epitaxial wafer formed by an epitaxial growth method such as a liquid phase epitaxial growth method.

  Compound semiconductors such as GaAs (gallium arsenide) and InGaAs (indium gallium arsenide) have a feature of higher electron mobility than Si (silicon) semiconductors. Taking advantage of this feature, GaAs and InGaAs are often used in devices that require high-speed operation and high-efficiency operation.

  A typical example is HEMT, which is used for a microwave amplifier for transmitting a mobile phone and a high-frequency amplifier for a receiving antenna for satellite broadcasting.

  A schematic structure of an HEMT epitaxial wafer (hereinafter abbreviated as HEMT epi) is shown in FIG.

  The HEMT epi is formed on the semi-insulating substrate 30 by sequentially epitaxially growing a buffer layer 31, a carrier supply layer 32, a spacer layer 33, a channel layer 34, a spacer layer 35, a carrier supply layer 36, and a contact layer 37. .

  The substrate 30 is a base for single crystal growth. The buffer layer 31 has a function of preventing deterioration of device characteristics due to residual impurities on the surface of the substrate 30 and a function of preventing leakage current from the channel layer 34. The channel layer 34 is a layer through which free electrons flow, and needs to be highly pure. The spacer layers 33 and 35 function to prevent the free electrons in the channel layer 34 from being ion-diffused by the n-type impurities in the carrier supply layers 32 and 36. The carrier supply layers 32 and 36 are doped with n-type impurities, and supply the generated free electrons to the channel layer 34. The contact layer 37 is a layer for forming an electrode.

  A method for growing the HEMT epi shown in FIG. 3 will be described below.

  A semi-insulating substrate 30 on which an epitaxial layer is grown is set on a susceptor and heated in a growth furnace. When the source gas is supplied into the growth furnace, the source gas is decomposed by heat, and epitaxial layers 31 to 37 are grown on the substrate 30.

In the conventional wafer, an epitaxial layer having a relatively high insulating property is grown on the buffer layer 31 using only one of an n-type layer and a p-type layer having a carrier concentration of 1E16 cm ⁻³ or less.

JP-A-5-13329 JP-A-6-163601 JP-A-6-188189 JP-A-6-181174 Japanese Examined Patent Publication No. 7-105552

However, in the conventional wafer, an n-type or p-type layer having a carrier concentration of 1E16 cm ⁻³ or less is used for the buffer layer 31 to increase the insulation property of the epi material itself, thereby forming a device wafer and a substrate formed thereon. Insulation of 30 was performed, but the insulation was not sufficient. Leakage current that leaked current to the buffer layer 31 during device operation often became a problem.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a III-V group compound semiconductor epitaxial wafer that can improve the insulating properties of a device by improving the buffer layer and reduce the leakage current during device operation.

To achieve the above object, the invention of claim 1 is a III-V group compound semiconductor in which a buffer layer, a channel layer, a spacer layer, a carrier supply layer, and a contact layer are epitaxially grown on a semi-insulating compound semiconductor substrate. the buffer layer, the carrier concentration of 1E17 cm ^-3 or less of n-GaAs, p-GaAs, or _{n-Al x Ga (1-} x) As, p-Al x Ga with _{(1-x) As p /} n It is a III-V compound semiconductor epitaxial wafer in which an interface is formed.

  The invention according to claim 2 is the III-V group compound semiconductor epitaxial according to claim 1, wherein the thickness of the p and n layers at the p / n interface formed in the buffer layer is 3 nm or more and the number of repeated structures is 5 times or more. It is a wafer.

The invention according to claim 3, as a group V raw material, AsH ₃ (arsine), As (CH _{3) 3} (trimethyl arsenic), TBA III -V compound according to claim 1 or 2 used (tertiary butyl arsine) It is a semiconductor epitaxial wafer.

In the invention of claim 4, the group III raw material includes Al (CH ₃ ) ₃ (trimethylaluminum), Ga (CH ₃ ) ₃ (trimethylgallium), In (CH ₃ ) ₃ (trimethylindium), Al (CH ₃ CH _{2) 3} (triethylaluminum), Ga (CH ₃ CH _{2) 3} (triethyl _{gallium), in (CH 3 CH 2} ) 3 (III -V compound according to any one of claims 1 to 3 using triethyl indium) It is a semiconductor epitaxial wafer.

  Invention of Claim 5 is a III-V group compound semiconductor epitaxial wafer in any one of Claims 1-4 which uses hydrogen, nitrogen, and argon as a gas for dilution of the raw material at the time of making it epitaxially grow.

  According to the present invention, the insulating property of the buffer layer can be improved by forming a number of low-concentration p / n junctions using a superlattice wafer in the buffer layer. That is, when the insulating property of the buffer layer is increased, the characteristics of the HEMT device are improved. By improving the characteristics of the HEMT device, it is possible to expect effects such as miniaturization of satellite dish receiving parabolic antennas and low power consumption of mobile phones.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows the structure of the HEMT epi.

Epi wafers for HEMT includes, over a substrate 10 made of GaAs, a spacer layer 13 consisting of the buffer layer 11, n-Al _0.25 Ga _0.75 carrier supply layer 12 composed of _{As, i-Al 0.40 Ga 0.60} As, i-In 0.30 A channel layer 14 made of Ga _0.70 As, a spacer layer 15 made of i-Al _0.40 Ga _0.60 As, a carrier supply layer 16 made of n-Al _0.25 Ga _0.75 As, a Schottky layer 17 made of i-Al _0.25 Ga _0.75 As, The cap layer (contact layer) 18 made of n-GaAs is formed by epitaxial growth.

In the present invention, in order to increase the insulating property of the buffer layer 11, a lower buffer layer 21 made of i-GaAs is formed on the substrate 10, and p ⁻ −Al _0.25 Ga _0.75 As is formed on the buffer layer 21. P-type buffer layer 22 and n ^-- Al _0.25 Ga _0.75 As n-type buffer layer 23 having a film thickness of 3 nm or more, preferably about 5 nm, and a wafer in which 5 layers or more, preferably about 20 layers are alternately repeated, The buffer layer 11 is configured by forming an upper buffer layer 24 made of i-Al _0.25 Ga _0.75 As on the top.

  Table 1 shows an example of this HEMT epitaxial wafer.

  Crystal growth is called epitaxial.

The epitaxial layer names n-, p-, and i- in Table 1 indicate that the epitaxial layer is n-type, p-type, and semi-insulating, respectively. The unit of thickness is nm (10 ^-9 m). The unit of carrier concentration is cm ⁻³ .

  A method for growing the HEMT epi shown in Table 1 will be described below.

  A semi-insulating substrate 10 on which an epitaxial layer is grown is set on a susceptor and heated in a growth furnace. When the source gas is supplied into the growth furnace, the source gas is decomposed by heat, and an epitaxial layer is grown on the substrate.

Here, AsH ₃ (arsine), As (CH ₃ ) ₃ (trimethylarsenic), and TBA (tertiary butylarsine) are used as the group V source of the source gas, and Al (CH ₃ ) is used as the group III source. ₃ (trimethylaluminum), Ga (CH _{3) 3} (trimethylgallium), an In (CH _{3) 3} (trimethyl _{indium), Al (CH 3 CH 2} ) 3 ( triethyl _{aluminum), Ga (CH 3 CH 2} ) 3 ( Triethylgallium) and In (CH ₃ CH ₂ ) ₃ (triethylindium) can be used.

In the present invention, a p / n material of 1E17 cm ⁻³ or less is alternately grown on the buffer layer 11 in order to improve the insulation during device operation, and a plurality of p / n junction buffer layers 22 and 23 having a low carrier concentration are formed. By inserting it into the individual buffer layers 11, a superlattice structure using a p / n interface is formed to increase the insulation.

As the raw material gas for forming a p / n layer, n-GaAs, p-GaAs , or _{n-Al x Ga (1-} x) As, be used _{p-Al x Ga (1-} x) As it can.

In addition, as a gas for diluting the source gas for forming the V and III source gases and the p / n layer during the epitaxial growth, H ₂ (hydrogen), N ₂ (nitrogen), Ar (argon) are used. Use.

  The measurement result of the leakage current of the HEMT epi grown on the wafer is shown in FIG.

  In the figure, the solid line a indicates the HEMT epi of the present invention, and the dotted line b indicates the conventional HEMT epi.

  From FIG. 2, it can be seen that the electron mobility of the present invention has less leakage current than the conventional example.

  The present invention is a method for manufacturing a HEMT epitaxial buffer layer, but can also be applied to other device wafers such as HBT (heterojunction bipolar transistor).

In this invention, it is a figure which shows one Embodiment of a HEMT structure. It is a figure which shows the comparison of the leakage current of this invention and the conventional HEMT. It is a figure which shows the conventional HEMT structure.

Explanation of symbols

10 substrate 11 buffer layer 12, 16 carrier supply layer 13, 15 spacer layer 14 channel layer 18 contact layer 22 p layer 23 n layer

Claims (5)

In a III-V group compound semiconductor in which a buffer layer, a channel layer, a spacer layer, a carrier supply layer, and a contact layer are epitaxially grown on a semi-insulating compound semiconductor substrate, the n ⁻ with a carrier concentration of 1E17 cm ⁻³ or less is formed in the buffer layer. GaAs, p-GaAs, or _{n-Al x Ga (1-} x) as, p-Al x Ga (1-x) III -V compound, characterized in that the formation of the p / n interface with as Semiconductor epitaxial wafer.   The III-V group compound semiconductor epitaxial wafer according to claim 1, wherein the thickness of the p and n layers at the p / n interface formed in the buffer layer is 3 nm or more and the number of repeated structures is 5 or more. The III-V group compound semiconductor epitaxial wafer according to claim 1 or 2, wherein AsH ₃ (arsine), As (CH ₃ ) ₃ (trimethylarsenic), or TBA (tertiary butylarsine) is used as the group V raw material. As group III raw materials, Al (CH ₃ ) ₃ (trimethylaluminum), Ga (CH ₃ ) ₃ (trimethylgallium), In (CH ₃ ) ₃ (trimethylindium), Al (CH ₃ CH ₂ ) ₃ (triethylaluminum) A III-V compound semiconductor epitaxial wafer according to any one of claims 1 to ₃ , wherein Ga (CH ₃ CH ₂ ) ₃ (triethylgallium) or In (CH ₃ CH ₂ ) ₃ (triethylindium) is used. The III-V group compound semiconductor epitaxial wafer according to any one of claims 1 to 4, wherein hydrogen, nitrogen, or argon is used as a gas for diluting a raw material for epitaxial growth.

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