JP3470054B2 - Nitride III-V compound semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nitride system III-
The present invention relates to a V-group compound semiconductor device, and more particularly to a semiconductor device using a two-dimensional electron gas that is excellent in high output, high frequency and high temperature characteristics.

[0002]

2. Description of the Related Art As a semiconductor device utilizing a two-dimensional electron gas, a heterostructure field effect transistor (HF) is used.
ET), high electron mobility transistors (HEMTs), and modulation doped field effect transistors (MODFETs). As a semiconductor device using such a two-dimensional electron gas, one using a GaAs-based material has been developed.

In a conventional GaAs HFET, generally, as shown in FIG. 6, an undoped GaAs buffer layer 102 (film thickness 1 μm, carrier concentration 3 × 10 ¹⁶ cm ^{−) is} sequentially formed on a semi-insulating GaAs substrate 101. ³ ), undoped A
lGaAs spacer layer 103 (film thickness 10 nm, carrier concentration 1 × 10 ¹⁷ cm ⁻³ ), n-type AlGaAs donor layer 10
4 (film thickness 20 nm, carrier concentration 1 × 10 ¹⁸ cm ^-3 ), n
A type GaAs cap layer 105 (film thickness 10 nm, carrier concentration 3 × 10 ¹⁸ cm ⁻³ ) is formed. In FIG. 6, 107 is a gate electrode and 108 is a source / drain electrode. Further, 500 is a two-dimensional electron gas.

Further, a structure of an HFET transistor having a structure similar to that of the GaAs-based HFET and using a nitride-based III-V group compound semiconductor has been conventionally reported (US Pat. No. 5,192,987). This nitride III-
As shown in FIG. 7, a transistor using a group V compound semiconductor has an AlN low temperature growth buffer layer 202 (film thickness 20 nm), an AlN low temperature growth buffer layer 202, and an insulating substrate 201 made of sapphire.
GaN buffer layer 203 (film thickness 2 μm, carrier concentration 8 ×
10 ¹⁶ cm ⁻³ ), AlGaN donor layer 204 (film thickness 20 n
m, carrier concentration 1 × 10 ¹⁸ cm ⁻³ ) are laminated, and GaN is used as a channel. In addition,
In FIG. 7, 500 is a two-dimensional electron gas.

As another transistor using a nitride-based III-V group compound semiconductor, as shown in FIG. 8, an AlN low temperature growth buffer layer 3 on an insulating substrate 301 is used.
02 (film thickness 20 nm), GaN buffer layer 303 (film thickness 3 μ
m), an AlN barrier layer 304 (thickness: 3 nm), and a GaN channel layer 305 (thickness: 100 nm), which has an inverted structure (Electron. Lett. 31 (1995) p. 1951).
In FIG. 8, 500 is a two-dimensional electron gas.

[0006]

By the way, as shown in FIG. 9, the electron mobility of GaN generally used as a channel layer is about 200 cm ² / Vs when the carrier concentration is 1 × 10 ¹⁸ cm ^-3 . Carrier concentration is 1 × 10 ¹⁷ cm ^-3
In this case, the electron mobility is about 400 cm ² / Vs, which is larger than that of other wide band gap materials such as SiC by about one digit. However, the electron mobility of this GaN channel is about an order of magnitude smaller than the electron mobility of the GaAs channel used in the GaAs HFET.

Further, in the GaAs-based HFET, as described in JP-A-63-161678,
InG, which has a higher electron mobility, is used as a channel material.
It has also been considered that an aAs mixed crystal is inserted into the AlGaAs / GaAs interface, and it is considered that the same method can be applied to a nitride semiconductor device.

However, in the nitride-based III-V group semiconductor device, there is a problem with the crystallinity or flatness of the InGaN mixed crystal, and the electron mobility is not necessarily high. Can not be expected to be effective. Because InGaN
This is because the composition of the mixed crystal becomes uneven depending on the place.

However, I having a uniform composition distribution
If an nGaN mixed crystal is obtained, it is considered that the electron mobility can be improved as compared with the GaN channel.

An object of the present invention is to provide a nitride-based III-V group compound semiconductor device having an InGaN mixed crystal having a uniform composition distribution and having a large channel electron mobility.

[0011]

As a result of intensive studies by the inventors, it has been found that the structure described below is effective for achieving the above object.

That is, the invention of claim 1 is InGaN
The InGaN channel layer is made of Al _x Ga _y In
It is characterized in that it is formed on a surface reactant layer formed on a _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) film.

According to the first aspect of the present invention, the InGaN channel layer is formed of Al _x Ga _y In _1-xy (0 ≦ x ≦ 1, 0 ≦ y ≦.
1) It is formed on the surface reactant layer formed on the film. As described above, by inserting the surface reactant layer between the substrate and the InGaN channel layer, it becomes possible to change the three-dimensional film growth into the two-dimensional film growth. The composition distribution can be made more uniform.

[0014] According to a second aspect of the invention, in the nitride-based III-V compound semiconductor device according to claim 1, Surface reactant layer, Li, Be, Na, Mg , K, C
It is composed of at least one of a, Zn, S, Se, and Te.

According to the second aspect of the present invention, the surface reactant layer is composed of Li, Be, Na, Mg, K, Ca, Zn, S,
Since it is composed of at least one of Se and Te, the three-dimensional film growth can be changed to the two-dimensional film growth, and the composition distribution of the InGaN channel layer can be made more uniform.

The surface reactant layer is made of Si,
When it is made of Ge or the like, it promotes three-dimensional film growth, and is not preferable as a surface reactant layer.

The invention of claim 3 is the same as claim 1 or
The nitride-based III-V group compound semiconductor device described in 2 is characterized in that the surface coverage of the surface reactant layer is 1 or less.

According to the third aspect of the present invention, since the surface coverage of the surface reactant layer is 1 or less, the crystallinity of the InGaN channel layer grown thereon is not deteriorated.

When the surface coverage of the surface reactant layer exceeds 1, the crystallinity of the InGaN channel layer grown thereon deteriorates. The surface reactant layer is a layer inserted to change the surface energy of the crystal.

In the present invention, InGaN is used as the channel material, but InGaN has no composition distribution.
Mobility is superior to that of GaN. The composition of In _x Ga _1-x N may be in the range of X> 0.

In this way, it is possible to obtain an InGaN film having a mobility higher than that of GaN having no composition distribution. By using this InGaN film as a channel layer, a nitride system III- having a large channel electron mobility can be obtained. V
A group compound semiconductor device can be realized.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail based on the illustrated embodiments.

[First Reference Example ] FIG. 1 shows a nitride-based HFE according to a first reference example of the present invention.
The cross section showing the outline of T is shown.

This nitride HFET comprises a (0001) sapphire substrate 11, a low temperature grown AlN buffer layer 12 having a film thickness of 20 nm, a carrier concentration of 5 × 10 ¹⁶ cm ^-3 and a film thickness of 2 μm.
Undoped GaN buffer layer 13, film thickness 20 nm / 2
Undoped GaN / InN multilayer films 14 of 0 nm and 5 periods are sequentially stacked. Furthermore, this undoped GaN /
Carrier concentration 4 × 10 ¹⁷ cm on the InN multilayer film 14.
^-3 , In _0.2 Ga _0.8 N channel layer 15 having a film thickness of 10 nm,
Carrier concentration 5 × 10 ¹⁶ cm ⁻³ , undoped GaN spacer layer 16 with film thickness 10 nm, carrier concentration 2 × 10 ¹⁸ c
m ⁻³ , 30 nm thick n-type GaN donor layer 17, Pt / A
u gate electrode 18, Ti / Al source / drain electrode 19
Are sequentially stacked. In addition, 50 is a two-dimensional electron gas.

As a crystal growth method for forming such a layered structure, MOVPE method, MBE method or the like can be used. In this reference example , M is used as a crystal growth method.
The OVPE method was used. The MOVPE process is as follows.

First, the temperature of the substrate 11 is set to 1100 ° C. in a hydrogen atmosphere, and the substrate cleaning is performed for 10 minutes. Next, the temperature of the substrate 11 was set to 550 ° C. and the low temperature buffer layer 12 was grown. Then, the temperature of the substrate 11 was set to 1000 ° C. and the GaN buffer layer 13 was grown. Then, the GaN / InN multilayer film 14 was grown at 700 ° C., and then the InGaN channel layer 15 was grown at a substrate temperature of 700 ° C. GaN spacer layer 1 thereon
The 6, GaN donor layer 17 was grown while raising the substrate temperature to 1000 ° C.

[0027] The same film structure as the nitride HFET of this reference example, as a result of hole measurement confirmed mobility 1200 cm ² / Vs in mobility 800 cm ² / Vs and 77K (absolute temperature) at room temperature.

In this reference example , an HFET having a gate length of 1 μm and a source-drain distance of 5 μm was used, and its characteristics were evaluated. As a result, the maximum oscillation frequency fmax at room temperature was obtained.
= 18 GHz, transconductance g _m = 150 m
S / mm, temperature 250 ° C., g _m = 100 mS / m
I got m.

On the other hand, in the comparative example employing the GaN channel layer instead of the InGaN channel layer 15, the maximum oscillation frequency fmax = 15 GHz, the transconductance g _m = 120 mS / mm, and the temperature 200 ° C., g _m = It was 80 mS / mm. Therefore this
The effect of the InGaN channel layer 15 adopted in the reference example was confirmed. In this reference example , the maximum operating temperature is 30
It was 0 ° C.

The carrier concentration and electron mobility of the undoped InGaN channel layer 15 are 4 × 10 ¹⁷ cm, respectively.
^-3 and 600 cm ² / Vs, and its electron mobility was about 1.5 times that of the GaN channel layer. This large mobility is considered to be the cause of greatly improving the characteristics of the HFET.

Further, as in this reference example , GaN / In
InGaN channel layer 1 grown on N multilayer film 14
The mobility of 5 was compared with the mobility of the InGaN channel layer directly grown on the GaN buffer layer 13 as a comparative example. As a result, the GaN / InN multilayer film 1 of this reference example
The mobility of the InGaN channel layer 15 on 4 is 2 times the mobility of the InGaN channel layer directly above the GaN layer of the comparative example.
It was double. This is a multi-layered GaN / InN layer 14
By adopting In, the dislocations from the interface of the substrate 11 are reduced, and as a result, In having less uneven composition distribution is obtained.
It is considered that this is because the GaN channel layer 15 could be produced.

[Second Reference Example ] Next, a nitride HFET according to a second reference example of the present invention will be described. The second reference example is the GaN / InN shown in FIG.
In-plane lattice constant of multilayer film 14 and InGaN channel layer 15
The difference from the above-described first reference example is only that the layer thicknesses of the GaN layer and the InN layer of the GaN / InN multilayer film 14 are set so that the in-plane lattice constants of 1 and 3 match.

As the crystal growth method for forming the layer structure as in this reference example , MOVPE method, MBE method or the like can be used. In the second reference example , the MOVPE method was used as the crystal growth method.

As a result of hole measurement using the same film structure as in the second reference example , the mobility at room temperature was 850 cm.
Mobility 1250 at ² / Vs and 77K (absolute temperature)
The cm ² / Vs was confirmed.

In this reference example , an HFET having a gate length of 1 μm and a source-drain distance of 5 μm was produced, and its characteristics were evaluated. As a result, at room temperature, the maximum oscillation frequency f
max = 20 GHz, transconductance g _m = 160
mS / mm, temperature 250 ° C., g _m = 105 mS /
It was mm.

On the other hand, instead of the InGaN channel layer 15, in the comparative example employing the GaN channel layer, at room temperature, the maximum oscillation frequency fmax = 15 GHz, transconductance gm = 120 mS / mm, at a temperature 200 ℃, g _m = 80mS It was / mm. Therefore, the effect of the InGaN channel layer 15 adopted in this reference example was confirmed. In this reference example , the maximum operating temperature is 3
It was 00 ° C.

In this second reference example , GaN / In
GaN / InN so that the in-plane lattice constant of the N multilayer film 14 matches the in-plane lattice constant of the InGaN channel layer 15.
The layer thicknesses of GaN and InN in the multilayer film 14 were set.
By matching the in-plane lattice constants of the channel layer 15 and the multilayer film 14, the strain existing in the InGaN channel layer 15 can be reduced. Therefore, the non-uniformity of the composition distribution caused by the strain can be suppressed, and a more uniform InGaN channel layer 15 with high mobility can be obtained. As a result, in the second reference example , the characteristics could be further improved as compared with the first reference example .

[Third Reference Example ] Next, FIG. 2 shows a cross section showing an outline of a nitride-based HFET which is a third reference example of the present invention.

The nitride-based HFET of the third reference example is
(0001) Sapphire substrate 21, low-temperature grown GaN buffer layer 22 having a film thickness of 20 nm, carrier concentration 5 × 10 ¹⁶ cm
^-3 , an undoped GaN buffer layer 23 having a film thickness of 2 μm, an undoped AlN / In film having a film thickness of 20 nm / 20 nm and 5 periods
The N layers 24 are sequentially stacked.

Further, on the undoped AlN / InN multilayer film 24, a carrier concentration of 4 × 10 ¹⁷ cm ⁻³ , an In _0.2 Ga _0.8 N channel layer 25 having a film thickness of 10 nm, a carrier concentration of 5 × 10 ¹⁶ cm ⁻³ , Undoped Ga with a film thickness of 10 nm
An N spacer layer 26, a carrier concentration of 2 × 10 ¹⁸ cm ⁻³ , an n-type GaN donor layer 27 having a film thickness of 30 nm, a Pt / Au gate electrode 28, and a Ti / Al source / drain electrode 29 are sequentially laminated.

As a crystal growth method for forming such a layered structure, MOVPE method, MBE method or the like can be used. In this third reference example , the MOVPE method was used as the crystal growth method. The MOVPE process is
It is as follows.

First, the temperature of the substrate 21 is set to 1 in a hydrogen atmosphere.
The substrate was cleaned at 100 ° C. for 10 minutes.
Next, the temperature of the substrate 21 was set to 550 ° C. and the low temperature buffer layer 22 was grown. Then, the temperature of the substrate 21 is set to 100.
The temperature was set to 0 ° C. and the GaN buffer layer 23 was grown. Then, the AlN / InN multilayer film 24 was grown at 700 ° C., and then the InGaN layer 25 was grown at a substrate temperature of 700 ° C. The growth of the GaN spacer layer 26 thereon was performed while raising the substrate temperature to 1000 ° C.

[0043] The same film structure as the nitride HFET of this reference example, as a result of hole measurement confirmed mobility 1250 cm ² / Vs in mobility 880 cm ² / Vs and 77K (absolute temperature) at room temperature.

In this reference example , an HFET having a gate length of 1 μm and a source-drain distance of 5 μm was used, and its characteristics were evaluated. As a result, the maximum oscillation frequency fmax was obtained at room temperature.
= 19 GHz, transconductance g _m = 155 m
S / mm, temperature 250 ° C., g _m = 110 mS / m
It was m.

On the other hand, in the comparative example employing the GaN channel layer instead of the InGaN channel layer 25, the maximum oscillation frequency fmax = 15 GHz, the transconductance g _m = 120 mS / mm, and the temperature 200 ° C., g _m = at room temperature. It was 80 mS / mm. Therefore, the effect of the InGaN channel layer 25 adopted in this third reference example was confirmed. Further, in this third reference example , the maximum operating temperature was 350 ° C.

Further, as in this reference example , AlN / In
InGaN channel layer 25 grown on N multilayer film 24
And the mobility of the InGaN channel layer grown directly on the GaN buffer layer 23 as a comparative example were compared. As a result, the mobility of the InGaN channel layer 25 on the AlN / InN multilayer film 24 of this reference example was determined by the InG grown directly on the GaN buffer layer 23 of the comparative example.
The mobility was 1.7 times the mobility of the aN channel layer. this is,
It is considered that by adopting the AlN / InN multilayer film 24 having the multilayer structure, dislocations from the interface of the substrate 21 are reduced, and as a result, the InGaN channel layer 25 with less uneven composition distribution can be manufactured. .

Further, in the third reference example , the GaN of the GaN / InN multilayer film 14 of the first and second reference examples is replaced with AlN, and the AlN / InN multilayer film 24 is adopted. Layer 25 and layer 23 below it,
It is possible to further improve the electrical insulating property with respect to 22. Therefore, according to the third reference example using the AlN / InN multilayer film 24, the InGaN channel layer 2 is different from the first and second reference examples using the GaN / InN multilayer film 14.
The mobility of No. 5 could be further increased.

[Fourth Reference Example ] Next, a nitride-based HFET according to a fourth reference example of the present invention will be described. In this fourth reference example , the AlN layer and the InN layer of the AlN / InN multilayer film 24 are arranged so that the in-plane lattice constant of the AlN / InN multilayer film 24 and the InGaN channel layer 25 shown in FIG. Only the point that the layer thickness of the layer is set is different from the above-mentioned third reference example .

As a crystal growth method for forming such a layered structure, MOVPE method, MBE method or the like can be used. In the fourth reference example , the MOVPE method was used as the crystal growth method.

As a result of hole measurement using the same film structure as in the fourth reference example , the mobility at room temperature was 950 cm.
Mobility 1400 at ² / Vs and 77K (absolute temperature)
The cm ² / Vs was confirmed.

In the fourth reference example , the gate length is 1 μm.
HFET with a distance between source and drain of 5 μm was manufactured and its characteristics were evaluated. As a result, at room temperature, maximum oscillation frequency fmax = 21 GHz, transconductance g _m
= 170 mS / mm, temperature 250 ° C., g _m = 13
It was 0 mS / mm.

On the other hand, in the comparative example using the GaN channel layer instead of the InGaN channel layer 25, the maximum oscillation frequency fmax = 15 GHz, the transconductance g _m = 120 mS / mm, and the temperature 200 ° C., g _m = at room temperature. It was 80 mS / mm. Therefore this
The effect of the InGaN channel layer 25 adopted in the reference example was confirmed. Further, in this reference example , the maximum operating temperature is 3
It was 80 ° C.

In this fourth reference example , AlN / In
AlN / InN so that the in-plane lattice constant of the N multilayer film 24 matches the in-plane lattice constant of the InGaN channel layer 25.
The layer thicknesses of AlN and InN of the multilayer film 24 were determined. Due to the matching of the in-plane lattice constants, the strain existing in the InGaN channel layer 25 can be reduced, the non-uniformity of the composition distribution caused by the strain can be suppressed, and a more uniform InGaN channel layer 25 with high mobility can be obtained. Obtainable. Further, in the fourth reference example , similarly to the third reference example , the insulating effect can be exhibited by the AlN / InN multilayer film 24 employing the AlN layer.

[Fifth Reference Example ] Next, FIG. 3 shows a cross section showing an outline of a nitride-based HFET which is a fifth reference example of the present invention.

The nitride-based HFET of the fifth reference example is
(0001) GaN substrate 31, carrier concentration 5 × 10 ¹⁶ c
m ⁻³ , 2 μm thick undoped GaN buffer layer 32,
Undoped AlN barrier layer 33 having a film thickness of 20 nm, film thickness 15
nm undoped InGaN channel layers 34 are sequentially stacked. Further, on the undoped InGaN channel layer 34, a Si-doped GaN cap layer 35 having a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ and a film thickness of 30 nm, Pt / A.
u gate electrode 36, Ti / Al source / drain electrode 37
Are sequentially stacked.

As the crystal growth method of such a film structure, the MOVPE method, the MBE method or the like can be used as in the first reference example .

[0057] The nitride HFET same film structure of the fifth reference example, as a result of hole measurement, check the mobility 1300 cm ² / Vs in mobility 900 cm ² / Vs and 77K (absolute temperature) at room temperature did.

In this reference example , an HFET having a gate length of 1 μm and a source-drain distance of 5 μm was used, and its characteristics were evaluated. As a result, the maximum oscillation frequency fmax at room temperature was obtained.
= 19 GHz, transconductance g _m = 155 m
S / mm, temperature 250 ° C., g _m = 110 mS / m
It was m. On the other hand, the undoped InGaN channel layer 3
When a GaN channel layer is adopted instead of No. 4, at room temperature, maximum oscillation frequency fmax = 15 GHz, transconductance g _m = 120 mS / mm, temperature 200
At ° C, g _m = 80 mS / mm.

[Sixth Reference Example ] Next, FIG. 4 shows a cross section showing an outline of a nitride-based HFET according to a sixth reference example of the present invention.

The nitride-based HFET of the sixth reference example is
(0001) GaN lateral growth substrate 41, carrier concentration 5 × 10 ¹⁶ cm ⁻³ , undoped GaN buffer layer 42 having a film thickness of 2 μm, undoped AlN barrier layer 4 having a film thickness of 20 nm
3, 15-nm thick undoped InGaN channel layer 4
4 are sequentially stacked.

Further, on the InGaN channel layer 44, a Si-doped GaN cap layer 45 having a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ and a film thickness of 10 nm, a Pt / Au gate electrode 46, a Ti / Al source / drain electrode 47. Are sequentially stacked.

[0001] GaN lateral growth substrate 4
The manufacturing method of 1 is as follows: Jpn.J.Appl.Phy
s. Vol. 36 (1997) p. 899. Further, as the crystal growth method of the above film structure, the MOVPE method, the MBE method or the like can be used as in the first reference example described above.

[0063] The same film structure as the nitride HFET of this reference example, as a result of hole measurement confirmed mobility 1250 cm ² / Vs in mobility 880 cm ² / Vs and 77K (absolute temperature) at room temperature.

In this reference example , an HFET having a gate length of 1 μm and a source-drain distance of 5 μm was used, and its characteristics were evaluated. As a result, the maximum oscillation frequency fmax at room temperature was obtained.
= 19 GHz, transconductance g _m = 155 m
S / mm, temperature 250 ° C., g _m = 110 mS / m
It was m.

On the other hand, in the comparative example employing the GaN channel layer instead of the InGaN channel layer 44, the maximum oscillation frequency fmax = 15 GHz, the transconductance g _m = 120 mS / mm, and the temperature gm _{m at} 200 ° C. at room temperature. = 80 mS / mm.

[0066] [implementation Embodiment Next, FIG. 5, the nitride-based H in the form of implementation of the invention
The cross section showing the outline of FET is shown.

[0067] nitride based HFET of implementation form of this, the sapphire substrate 51, an undoped GaN low temperature buffer layer 52 having a thickness of 20 nm, a carrier concentration of 5 × 10 ¹⁶ cm ^-3, an undoped GaN buffer layer 53 having a thickness of 1 [mu] m, Coverage 0.
Surface reactant layer 54 composed of 33 Li atoms
Are sequentially stacked.

Further, this surface reactant layer 5
4 on top of it, an undoped InGaN channel layer 55 having a film thickness of 30 nm, a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ and a film thickness of 10 n
m of Si-doped GaN cap layer 56, Pt / Au gate electrode 57, and Ti / Al source / drain electrode 58 are sequentially stacked.

[0069] In the implementation form of this, the film structure was produced by RF-MBE method. The process of the RF-MBE method is as follows.

First, the temperature of the substrate 51 is set to 8 in vacuum.
The substrate is cleaned at 100 ° C. for 10 minutes. Next, the temperature of the substrate 51 is set to 550 ° C., and in order to improve the crystal growth, the substrate 51 is irradiated with nitrogen radicals to nitride the substrate surface. After that, the GaN (or AlN) low temperature buffer layer 52 was grown. Next, the substrate temperature was raised to 750 ° C. while irradiating with nitrogen radicals to grow the GaN buffer layer 53. Then, this GaN buffer layer 5
After growing 3, the substrate temperature was set to 600 ° C. and Li
Irradiate the beam to achieve the desired surface coverage
It was adjusted using a surface reconstruction pattern of EED (reflection high energy electron diffraction). This desired surface coverage was determined from the reconstructed pattern of RHEED. Then, subsequently, the InGaN channel layer 55 is grown at a substrate temperature of 600 ° C.,
Finally, the GaN cap layer 56 was grown while raising the substrate temperature to 750 ° C.

[0071] The same film structure as the nitride HFET of implementation form of this, as a result of the hole measurement, check the mobility 1150 cm ² / Vs in mobility 800 cm ² / Vs and 77K (absolute temperature) at room temperature did.

In this embodiment, the gate length is 1 μm,
As a result of evaluating the characteristics of an HFET with a source-drain distance of 5 μm, the maximum oscillation frequency fma at room temperature was obtained.
x = 18 GHz, transconductance g _m = 155 m
S / mm, temperature 250 ° C., g _m = 105 mS / m
It was m.

On the other hand, in the comparative example using the GaN channel layer instead of the InGaN channel layer 55, the maximum oscillation frequency fmax = 15 GHz, the transconductance g _m = 120 mS / mm, and the temperature 200 ° C., g _m = It was 80 mS / mm. Therefore, this
It was confirmed the effect of the InGaN channel layer 55 employed in the implementation form. Also, in the implementation form of this, the maximum operating temperature was 280 ° C..

[0074] In the implementation form of this, the Surface reactant layer 54, but using Li atom coverage 0.33, other coverage 1 following Be, Na, Mg, K,
Similar effects were obtained using Ca, Zn, S, Se and Te atoms.

In the first to sixth reference examples and the above embodiments , the semiconductor device utilizing the two-dimensional electron gas is the heterostructure field effect transistor (HFET). It can also be applied to a transistor (HEMT) and a modulation-doped field effect transistor (MODFET).

[0076]

As is clear from the above, according to the invention of claim 1 , the InGaN channel layer has Al _x Ga _y In _1-xy (0
≦ x ≦ 1,0 ≦ y ≦ 1) formed on the surface reactive layer formed on the film. As described above, by inserting the surface reactant layer between the substrate and the InGaN channel layer, it becomes possible to change the three-dimensional film growth into the two-dimensional film growth.
The composition distribution of the GaN channel layer can be made more uniform.

[0077] Further, the invention of claim 2, in the nitride-based III-V compound semiconductor device according to claim 1, Surface reactant layer, Li, Be, Na, Mg , K, C
It is composed of at least one of a, Zn, S, Se, and Te.

According to the second aspect of the present invention, the surface reactant layer is composed of Li, Be, Na, Mg, K, Ca, Zn, S,
Since it is composed of at least one of Se and Te, the three-dimensional film growth can be changed to the two-dimensional film growth, and the composition distribution of the InGaN channel layer can be made more uniform.

The surface reactant layer is made of Si,
When it is made of Ge or the like, it promotes three-dimensional film growth, and is not preferable as a surface reactant layer.

The invention of claim 3 is the same as claim 1 or
In the nitride-based III-V group compound semiconductor device according to 2, the surface coverage of the surface reactant layer is 1 or less, and therefore the crystallinity of the InGaN channel layer grown thereon is not deteriorated. .

In the present invention, InGaN is used as the channel material, but InGaN has no composition distribution.
Mobility is superior to that of GaN. The composition of In _x Ga _1-x N may be in the range of X> 0.

In this way, it is possible to obtain an InGaN film having a mobility higher than that of GaN having no composition distribution. By using this InGaN film as a channel layer, a nitride system III- having a large channel electron mobility can be obtained. V
A group compound semiconductor device can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an element structure of an HFET which is a first reference example of a nitride-based III-V group compound semiconductor device of the present invention.

FIG. 2 is a sectional view showing an element structure of an HFET of a third reference example of the present invention.

FIG. 3 is a sectional view showing an element structure of an HFET of a fifth reference example of the present invention.

FIG. 4 is a sectional view showing an element structure of an HFET of a sixth reference example of the present invention.

5 is a cross-sectional view showing the element structure of HFET of implementation embodiment of the present invention.

FIG. 6 is a diagram showing a structure of a conventional GaAs HFET.

FIG. 7 is a diagram showing a conventional example of a GaN-based HFET.

FIG. 8 is a diagram showing a conventional example of a GaN-based inverted structure HFET.

FIG. 9 is a diagram showing a relationship between carrier concentration and mobility in GaN.

[Explanation of symbols]

11 ... (0001) Sapphire substrate, 12 ... Low temperature growth Al
N buffer layer, 13 ... Undoped GaN buffer layer, 1
4 ... Undoped GaN / InN layer, 15 ... Undoped I
nGaN channel layer, 16 ... Undoped GaN spacer layer, 17 ... N-type GaN donor layer, 18 ... Gate electrode,
Reference numeral 19 ... Source / drain electrodes, 21 ... (0001) sapphire substrate, 22 ... Low temperature grown GaN buffer layer, 23 ... Undoped GaN buffer layer, 24 ... AlN / InN layer,
25 ... Undoped InGaN channel layer, 26 ... Undoped GaN spacer layer, 27 ... N-type GaN donor layer,
28 ... Gate electrode, 29 ... Source / drain electrode, 31
(0001) GaN substrate, 32 ... Undoped GaN buffer layer, 33 ... Undoped AlN barrier layer, 34 ... Undoped InGaN channel layer, 35 ... Si-doped GaN cap layer, 36 ... Pt / Au gate electrode, 37 ... Ti / A
l source / drain electrodes, 41 ... (0001) GaN lateral growth substrate, 42 ... Undoped GaN buffer layer, 4
3 ... Undoped AlN barrier layer, 44 ... Undoped InG
aN channel layer, 45 ... Si-doped GaN cap layer,
46 ... Pt / Au gate electrode, 47 ... Ti / Al source / drain electrode, 51 ... Sapphire substrate, 52 ... Undoped GaN low temperature buffer layer, 53 ... Undoped GaN buffer layer, 54 ... Surface reactant layer, 55 ... Undoped InGaN channel Layers, 56 ... Si-doped GaN cap layer, 57 ... Pt / Au gate electrode, 58 ... Ti / A
l Source / drain electrodes.

Continued Front Page (56) References JP 10-41230 (JP, A) JP 9-199759 (JP, A) JP 10-214999 (JP, A) IEICE Transactions, Japan , January 25, 1998, Vol. J81-CII, No. 1, p. 58-64 WILLIAM A, Doolittle et. al, Growth of GaN on lithium gallates substrates for development of a GaN thin compliant substrate, Journal of Vacuum, October, 1998, October, October & October. 16, No. 3, p. 1300-1304 (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/338 H01L 29/778 H01L 29/812

Claims (3)

(57) [Claims] 1. A InGaN channel layer made of InGaN _{is, Al x Ga y In 1-} xy N (0 ≦ x ≦ 1,0 ≦ y ≦ 1)
A nitride-based III-V compound semiconductor device formed on a surface reactant layer formed on a film. 2. The nitride-based III-V group compound semiconductor device according to claim 1 , wherein the surface reactant layer is Li, Be, Na, M.
A nitride-based III-V group compound semiconductor device comprising at least one of g, K, Ca, Zn, S, Se, and Te. 3. The nitride system III according to claim 1 or 2.
-V group compound semiconductor device, wherein the surface coverage of the surface reactant layer is 1 or less.