JP2003179082A - High electron mobility transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GaN high electron mobility transistor having a high electron mobility of an electron transit layer. <P>SOLUTION: The high electron mobility transistor comprises the electron transit layer made of a GaN compound semiconductor layer, and an electron supply layer made of a GaN compound semiconductor layer having a larger band gap energy than that of the electron transit layer in such a manner that the electron transit layer contains an In of 1×10<SP>19</SP>to 5×10<SP>20</SP>cm<SP>-3</SP>. Or, the electron transit layer contains an As or P of 1×10<SP>19</SP>to 5×10<SP>20</SP>cm<SP>-3</SP>. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high electron mobility transistor (High Electron Mobility) having enhanced electron mobility.
Transistor: HEMT).

[0002]

2. Description of the Related Art High electron mobility transistors (hereinafter referred to as HE
MT) is a low-noise high-power microwave device.
It is used in satellite broadcasting receivers. This element
As an HEMT epitaxial wafer for fabrication
AlGaAs / GaAs type is mainly used for
Came. By the way, recently, it operates at higher temperature than GaAs.
GaN-based epitaxy that is capable of
Luwafer is drawing attention. This GaN HEMT
Is a semi-insulating sapphire group, for example, as shown in FIG.
An AlN buffer layer 2 on the plate 1 and a non-electrode which becomes an electron transit layer.
GaN layer 3, n-AlGaN layer 4 serving as an electron supply layer
Are sequentially laminated. In addition, 5, 6 and 7 are each
The source electrode, the gate electrode and the drain electrode.
It In the HEMT having the above structure, n serving as an electron supply layer
-AlGaN layer 4 is non-doped GaN that serves as an electron transit layer
The electrons are supplied to the layer 3, and the supplied electrons are the maximum of the GaN layer 3.
The upper layer portion 3a (a region in contact with the n-AlGaN layer 4) is highly transferred.
Drive with mobility. Therefore, the GaN layer 3 has a high electron mobility.
High purity and few crystal defects are required to maintain
To be done. This HEMT is manufactured as follows. Immediately
Then, first, using a metalorganic vapor phase epitaxy method, a sapphire substrate
AlN buffer layer 2, non-doped GaN layer 3, n
-The AlGaN layer 4 is sequentially laminated. Then plasma C
SiO using VD equipment ₂ Film deposition, photoresist
And patterning by chemical etching. That
After that, a metal such as AuGe / Ni is vapor-deposited to form a source electrode.
5, the gate electrode 6 and the drain electrode 7 are formed.

[0003]

[Problems to be Solved by the Invention] However, GaN
When the layer is vapor-deposited, it is difficult for nitrogen N to enter the grown crystal, and a lattice defect due to the lack of N occurs. Therefore, in the HEMT described above, the GaN layer serving as the electron transit layer is mainly composed of N.
However, there is a problem that there are lattice defects due to the vacancy.

[0004]

The present invention solves the above problems.
The electron transit layer is a GaN-based compound.
It consists of a semiconductor layer, and the electron supply layer is
GaN-based compound semiconductor with large band gap energy
A high electron mobility transistor comprising layers,
In the running layer, In, As or P is 1 × 10¹⁹cm^-3Since
Top 5 × 10²⁰cm ^-3High electron transfer characterized by including
It is a mobility transistor.

The present invention is based on new experimental findings. That is, when the present inventors add In to GaN,
In concentration is 1 × 10 ¹⁹ cm ⁻³ or more, 5 × 10 ²⁰ cm ⁻³
When the crystallinity was compared by the photoluminescence (PL) intensity in the following range, it was found that the PL intensity, which is considered to be a defect due to nitrogen in GaN, was significantly reduced. PL intensity I _B at the band edge of GaN (wavelength: about 36
5 nm) and PL intensity of nitrogen defects I _V (wavelength: about 57
5 nm), I _V
/ I _B = 0.1 to 0.2, while GaN containing In in the above range exceeds I _V / I beyond the measurement limit.
_B ≈ 0. From this fact, GaN has an I content within the above range.
It can be seen that the nitrogen-based defects in GaN are reduced by adding n. Therefore, when the electron transit layer is made of such GaN, it can be expected that the electron transit layer exhibits high electron mobility. Instead of adding In to GaN, As or P was 10 ¹⁹ cm ⁻³ or more, 5 × 10 5 or more.
Similar results can be obtained even when added in the range of ²⁰ cm ^-3 or less. In addition, other G such as AlGaN is formed in the electron transit layer.
Even if an aN-based compound semiconductor is used, In, As or P can be added within the above range to obtain the same result as GaN.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the H according to the present invention.
FIG. 3 is a cross-sectional view of one embodiment of EMT. In the figure, 11 is a semi-insulating silicon substrate, 12 is a GaN buffer layer, 13 is an In-doped GaN layer that serves as an electron transit layer, 14 is an n-AlGaN layer that serves as an electron supply layer, and 15, 16 and 17 are sources, respectively. , Gate and drain electrodes. This H
The EMT was manufactured by the following steps. That is, 1) using an ultra-high vacuum device having a growth chamber and a patterning chamber,
The following epitaxial wafer was produced by the molecular beam epitaxial growth method. On the semi-insulating silicon substrate 11, dimethylhydrazine (5 × 10 ⁻⁵ Torr) and Ga
Using (5 × 10 ⁻⁷ Torr), a GaN buffer layer 12 having a thickness of 50 Å is stacked at a growth temperature of 640 ° C. Then, on the GaN buffer layer 12, ammonia (5 × 1
0 ^-5 Torr), Ga (5 x 10 ^-7 Torr), and In (about 10 ^-9 Torr) at a growth temperature of 780 ° C.
Then, an In-doped GaN layer 13 having a thickness of 500 Å is laminated. Then, on the In-doped GaN layer 13, ammonia (5 × 10 ⁻⁵ Torr) and Ga (5 × 10 ⁻⁷ Tor) are formed.
r), Al (1 × 10 ⁻⁷ Torr) and Si (5 × 1)
0 ^-9 Torr) at a growth temperature of 850 ° C and 250 Å
The n-AlGaN layer 14 having a thickness of 1 is stacked. 2) Next, using a plasma CVD apparatus, after depositing SiO ₂ on the epitaxial wafer, the gate portion is masked by using photolithography and chemical etching, and openings are formed in the portions to be the source and drain. Al is vapor-deposited in the opening to form the source electrode 15 and the drain electrode 17. Then, the mask is removed, and conversely, a SiO ₂ mask is formed which covers the source electrode 15 and the drain electrode 17 and has an opening at a portion to be a gate, and Au is vapor-deposited to form the gate electrode 16. To do.

In the HEMT described above, In-doped Ga
The electron mobility of the In-doped GaN layer 13 serving as the electron transit layer was measured at a temperature of 77K by changing the amount of In added to the N layer 13. The results are shown in Table 1. As can be seen from Table 1, the amount of In added is 1 × 10 ¹⁹ cm ⁻³ or more, 5 × 10 ²⁰
In the range of cm ⁻³ or less, the electron mobility was 5500 or more, which was more than twice that in the case where In was not added, and high electron mobility was exhibited.

[0008]

[Table 1] Note) In addition amount: cm ^-3 Electron mobility (77K): cm ² /
V ^-1 / S ^-1

The present invention is not limited to the above-described embodiment, and the GaN layer serving as the electron transit layer is replaced by As instead of In.
Alternatively, P may be added at 10 ¹⁹ cm ⁻³ or more and 5 × 10 ²⁰ cm ⁻³ or less. At the time of this addition, solid As, arsine, organic As can be used as an As source,
As the P source, solid P, phosphine, or organic P can be used. The electron supply layer is AlG
A GaN layer may be used instead of the aN layer. However, in this case, a material having a smaller band gap than GaN,
For example, an In _1-X Ga _X N (0.1 ≦ X ≦ 0.3) layer is interposed between the In _{1 -X} Ga _X N (0.1 ≦ X ≦ 0.3) layer and an In-doped GaN layer that is an electron transit layer,
It is desirable that electrons are confined between the electron supply layer and the electron transit layer. Further, the above-described embodiment is HE
Although the high electron mobility In-doped GaN layer is used as the electron transit layer of the MT, the high electron mobility In-doped GaN layer may be used as the electron transit layer of another electronic device such as an FET.

[0010]

According to the present invention, there is an excellent effect that a GaN-based high electron mobility transistor having a high electron mobility in the electron transit layer can be obtained.

[0011]

[Brief description of drawings]

FIG. 1 is a cross-sectional view of one embodiment of a HEMT according to the present invention.

FIG. 2 is a cross-sectional view of a HEMT.

[Explanation of symbols]

11 Semi-insulating silicon substrate 12 GaN buffer layer 13 In-doped GaN layer 14 n-AlGaN layer 15, 16, 17 electrodes

Claims (2)

[Claims] 1. A high electron mobility transistor in which an electron transit layer comprises a GaN-based compound semiconductor layer and an electron supply layer comprises a GaN-based compound semiconductor layer having a bandgap energy larger than that of the electron transit layer. Layer is I
A high electron mobility transistor comprising n of 1 × 10 ¹⁹ cm ⁻³ or more and 5 × 10 ²⁰ cm ⁻³ or less. 2. A high electron mobility transistor comprising an electron transit layer made of a GaN compound semiconductor layer and an electron supply layer comprising a GaN compound semiconductor layer having a bandgap energy larger than that of the electron transit layer. Layer is A
s or P is 1 × 10 ¹⁹ cm ^-3 or more, 5 × 10 ²⁰ cm ^-3
A high electron mobility transistor comprising: