JP2010045416A - Group iii nitride electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gallium nitride electronic device of a low loss. <P>SOLUTION: In a group III nitride heterojunction transistor 11a, a second Al<SB>Y1</SB>In<SB>Y2</SB>Ga<SB>1-Y1-Y2</SB>N layer 15 forms a heterojunction 21 with a first Al<SB>X1</SB>In<SB>X2</SB>Ga<SB>1-X1-X2</SB>N layer 13a. A first electrode 17 forms a Schottky junction on the first Al<SB>X1</SB>In<SB>X2</SB>Ga<SB>1-X1-X2</SB>N layer 13a. The first Al<SB>X1</SB>In<SB>X2</SB>Ga<SB>1-X1-X2</SB>N layer 13a and the second Al<SB>Y1</SB>In<SB>Y2</SB>Ga<SB>1-Y1-Y2</SB>N layer 15 are located on a substrate 23. Electrodes 17a, 18a, and 19a contain a source electrode, a gate electrode, and a drain electrode respectively. The carbon concentration N<SB>C13</SB>of the first Al<SB>X1</SB>In<SB>X2</SB>Ga<SB>1-X1-X2</SB>N layer 13a is less than 1×10<SP>17</SP>cm<SP>-3</SP>. The dislocation density D of the second Al<SB>Y1</SB>In<SB>Y2</SB>Ga<SB>1-Y1-Y2</SB>N layer 15 is 1×10<SP>8</SP>cm<SP>-2</SP>. A two-dimensional electron gas layer 25 is produced by the heterojunction 21. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to group III nitride electronic devices.

  Non-Patent Document 1 describes a heterojunction field effect transistor (HFET). In order to obtain high output in the gallium nitride-based HFET, it is necessary to reduce the current collapse generated in the gallium nitride-based electronic device. One cause of current collapse that occurs when a gallium nitride HFET is operated at a high frequency and a large current is that electrons are trapped in the AlGaN region near the drain due to the influence of the electric field from the gate electrode end. . When electrons are trapped in the trap level on the AlGaN surface, the two-dimensional electron gas concentration decreases, which causes a decrease in output. The measurement of the potential distribution performed while energizing in the range of +100 volts to -100 volts is shown. According to this measurement, the potential distribution of a minute portion of the device is shown. After applying a stress voltage, a negative potential region generated by trapping electrons is generated on the AlGaN surface. The probability of electron emission from the trap level correlates with the amount of reverse leakage current of the Schottky electrode. When the leakage current is improved, the current collapse becomes more apparent.

  Non-Patent Document 2 shows that in an AlGaN / GaN heterostructure field effect transistor, there is a correlation between charge charging at the surface and current collapse.

“Development of Low Power Consumption High Frequency Devices Using Nitride Semiconductors” Project Proceedings of Final Report Meeting Page 84-85, Current Collapse Analysis of AlGaN / GaN HFETs by Planar KFM Method S. Sabuktagin et al. Appl. Phys. Lett. Vol. 75, 4016 (1999)

  As understood from Non-Patent Documents 1 and 2, the occurrence of current collapse is related to charge charging. Further, as shown in Non-Patent Document 1, the leakage current and the current collapse are in a trade-off relationship with each other.

  Specifically, in order to fabricate a low-loss gallium nitride-based electronic device, it is necessary to suppress current collapse in order to reduce the series resistance when a forward bias is applied, and simultaneously reduce the reverse leakage. is necessary. However, the adoption of process conditions that reduce the leakage current increases the degree of current collapse and increases the series resistance. Conversely, the use of process conditions that reduce current collapse causes an increase in leakage current. In other words, they are in a trade-off relationship.

  Advances in GaN-based crystal fabrication techniques have provided low dislocation density GaN wafers. In addition, GaN templates with a low dislocation density can be produced due to advances in crystal growth technology. On the GaN wafer and GaN template having a low dislocation density, a GaN-based crystal having a low dislocation density can be produced using substantially the same growth conditions as those for GaN-based crystal growth on a sapphire substrate or a silicon carbide substrate. . Since the GaN crystal has a low dislocation density, the leakage current in the gallium nitride electronic device is reduced. However, as a result, the current collapse increases.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a low-loss group III nitride electronic device with reduced current collapse.

A group III nitride electronic device according to one aspect of the present invention includes: (a) a first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1 ) Layer, and (b) a second Al _Y1 In _Y2 Ga _1-Y1-Y2 N (0 ≦ Y1 <1,0) forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer. ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer, (c) a first electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer, and (d) the first A second electrode provided on the Al _X1 In _X2 Ga _1-X1-X2 N layer, and (e) a substrate. The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided on the substrate, and the substrate is a GaN substrate having a dislocation density of 1 × 10 ⁸ cm ⁻² or less, 1 × 10 ⁸ cm ^−. AlN substrate having ^two or less of dislocation density, 1 × ¹⁰ 8 ^{cm -2} AlGaN substrate having the dislocation density, InGaN substrate having a dislocation density of 1 × ¹⁰ 8 ^{cm -2} or less, and 1 × ¹⁰ 8 ^{cm -2} The first Al _X1 In _X2 Ga _1-X1-X2 N layer is on the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer. , The band gap of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is larger than the band gap of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer, A two-dimensional electron gas layer is generated at the heterojunction between the Al _X1 In _X2 Ga _1-X1-X2 N layer and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer, and the first Al _X1 The In _X2 Ga _1-X1-X2 N layer is non-doped, the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is non-doped, and the first Al _X1 In _X2 Ga _1-X1-X2 The carbon concentration of the N layer is less than 1 × 10 ¹⁷ cm ⁻³ , the dislocation density of the second Al _Y1 In _Y2 Ga _{1−Y1 −Y2} N layer is less than 1 × 10 ⁸ cm ⁻² , The first electrode forms a Schottky junction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer.
In addition, a group III nitride electronic device according to one aspect of the present invention includes: (a) a first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1) layer; and (b) second Al _Y1 In _Y2 Ga _1-Y1-Y2 N (0 ≦ Y1 <1) forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer. , 0 ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer, (c) a first electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer, and (d) the above And a second electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer, the first Al _X1 In _X2 Ga _1-X1-X2 N layer comprising the second Al _{Y1 in Y2 Ga 1-Y1-} Y2 N is on a layer, the first _Al X1 _in X2 Ga Band gap of _-X1-X2 N layer is greater than the band gap of the second _{Al Y1 In Y2 Ga 1-Y1} -Y2 N layer, a carbon of the first _{Al X1 In X2 Ga 1-X1} -X2 N layer The concentration is less than 1 × 10 ¹⁷ cm ⁻³ , the dislocation density of the second Al _Y1 In _Y2 Ga _{1−Y1 −Y2} N layer is less than 1 × 10 ⁸ cm ⁻² , and the first electrode is Then, a Schottky junction is formed in the first Al _X1 In _X2 Ga _1-X1-X2 N layer.

The invention according to another aspect of the present invention is a group III nitride semiconductor epitaxial substrate for a group III nitride electronic device having a Schottky electrode, comprising: (a) a substrate; and (b) provided on the substrate. A first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1) layer; and (c) provided on the substrate, Second Al _Y1 In _Y2 Ga _1-Y1-Y2 N forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer (0 ≦ Y1 <1, 0 ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer, and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided between the first Al _X1 In _X2 Ga _1-X1-X2 N layer and the substrate. and it has the first _Al X1 _in X2 _{Ga 1-X1-} The band gap of ₂ N layer larger than the band gap of the second _{Al Y1 In Y2 Ga 1-Y1} -Y2 N layer, a silicon concentration in the first _{Al X1 In X2 Ga 1-X1} -X2 N layer is 1 × 10 ¹⁷ cm ⁻³ or more, and the dislocation density of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N is less than 1 × 10 ⁸ cm ⁻² .

Since carbon works to trap carriers in the gallium nitride semiconductor, leakage current is reduced in the gallium nitride semiconductor to which carbon is added. Therefore, carbon addition has been used to reduce leakage current. On the other hand, according to this group III nitride electronic device and group III nitride semiconductor epitaxial substrate, the dislocation density of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N layer is less than 1 × 10 ⁸ cm ^−2. Therefore, the leakage current due to dislocation is sufficiently low. Therefore, even if the carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer grown thereon is lowered to less than 1 × 10 ¹⁷ cm ⁻³ , the increase in leakage current is small. In the first Al _X1 In _X2 Ga _1-X1-X2 N layer, the number of electron capture levels is reduced. Electrons are trapped in the trap level by the voltage applied via the first and second electrodes. However, since the carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is less than 1 × 10 ¹⁷ cm ⁻³ , the number of trapped electrons is small, and therefore the influence of current collapse is reduced. Is done.

A group III nitride electronic device according to one aspect of the present invention includes: (a) a first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1 ) Layer, and (b) a second Al _Y1 In _Y2 Ga _1-Y1-Y2 N (0 ≦ Y1 <1,0) forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer. ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer, (c) a first electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer, and (d) the first And a second electrode provided on the Al _X1 In _X2 Ga _1-X1-X2 N layer, wherein the first Al _X1 In _X2 Ga _1-X1-X2 N layer is the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N is on a layer, the first _Al X1 _in X2 _{Ga 1-X -X2} bandgap of N layer is greater than the band gap of the second _{Al Y1 In Y2 Ga 1-Y1} -Y2 N layer, a silicon concentration in the first _{Al X1 In X2 Ga 1-X1} -X2 N layer 1 × 10 ¹⁷ cm ⁻³ or more, the dislocation density of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N is less than 1 × 10 ⁸ cm ⁻² , and the first electrode includes the first electrode A Schottky junction is formed in _one Al _X1 In _X2 Ga _1-X1-X2 N layer.

The invention according to another aspect of the present invention is a group III nitride semiconductor epitaxial substrate for a group III nitride electronic device having a Schottky electrode, comprising: (a) a substrate; and (b) provided on the substrate. A first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1) layer; and (c) provided on the substrate, Second Al _Y1 In _Y2 Ga _1-Y1-Y2 N forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer (0 ≦ Y1 <1, 0 ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer, and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided between the first Al _X1 In _X2 Ga _1-X1-X2 N layer and the substrate. and it has the first _Al X1 _in X2 _{Ga 1-X1-} The band gap of ₂ N layer larger than the band gap of the second _{Al Y1 In Y2 Ga 1-Y1} -Y2 N layer, a silicon concentration in the first _{Al X1 In X2 Ga 1-X1} -X2 N layer is 1 × 10 ¹⁷ cm ⁻³ or more, and the dislocation density of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N is less than 1 × 10 ⁸ cm ⁻² .

Since silicon works to provide carriers in the gallium nitride semiconductor, the resistivity of the gallium nitride semiconductor decreases in the gallium nitride semiconductor to which silicon is added. Therefore, in a gallium nitride semiconductor with a high dislocation density, a large leakage current is generated by carriers from silicon. On the other hand, according to the group III nitride electronic device and the group III nitride semiconductor epitaxial substrate, the dislocation density of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is 1 × 10 ⁸ cm ⁻² . The leakage current due to dislocation is sufficiently low. Therefore, even if the silicon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer grown thereon is increased to 1 × 10 ¹⁷ cm ⁻³ or more, the increase in leakage current is small. For this reason, in the first Al _X1 In _X2 Ga _1-X1-X2 N layer, the relaxation time of electrons trapped in the trap level is reduced. Electrons are trapped in the trap level by the voltage applied via the first and second electrodes. However, since the silicon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is 1 × 10 ¹⁷ cm ⁻³ or more, after the applied voltage disappears, the trapped electrons are detrapped in a short time. Therefore, the influence of current collapse is reduced.

A group III nitride electronic device according to one aspect of the present invention includes: (a) a first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1 ) Layer, and (b) a second Al _Y1 In _Y2 Ga _1-Y1-Y2 N (0 ≦ Y1 <1,0) forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer. ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer, (c) a first electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer, and (d) the first A second electrode provided on the Al _X1 In _X2 Ga _1-X1-X2 N layer, and (e) a substrate. The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided on the substrate, and the substrate is a GaN substrate having a dislocation density of 1 × 10 ⁸ cm ⁻² or less, 1 × 10 ⁸ cm ^−. AlN substrate having ^two or less of dislocation density, 1 × ¹⁰ 8 ^{cm -2} AlGaN substrate having the dislocation density, InGaN substrate having a dislocation density of 1 × ¹⁰ 8 ^{cm -2} or less, and 1 × ¹⁰ 8 ^{cm -2} The first Al _X1 In _X2 Ga _1-X1-X2 N layer is on the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer. , The band gap of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is larger than the band gap of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer, _{Al X1 In X2 Ga 1-X1} -X2 silicon concentration N layer is greater than the carbon concentration of the first _{Al X1 In X2 Ga 1-X1} -X2 N layer, the first _Al X1 _In X2 _{Ga 1- A} two-dimensional electron gas layer is generated at the heterojunction between the _X1-X2 N layer and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer, and the second Al _Y1 In _Y2 Ga _{1-Y1- Y2} N layer is undoped, the carbon concentration of the first _{Al X1 in X2 Ga 1-X1} -X2 N layer is not 3 × ¹⁰ 16 ^{cm -3} or more, the first _Al X1 _in X2 _{Ga 1-} The carbon concentration of the _X1-X2 N layer is 1 × 10 ¹⁹ cm ⁻³ or less, and the silicon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is 1 × 10 ¹⁷ cm ⁻³ or more. The first _{l X1 In X2 Ga 1-X1} -X2 silicon concentration N layer is 1 × ¹⁰ 19 ^{cm -3} or less, the dislocation density of the second _{Al Y1 In Y2 Ga 1-Y1} -Y2 N is 1 × 10 ⁸ less than cm ⁻² , and the first electrode forms a Schottky junction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer.
In addition, a group III nitride electronic device according to one aspect of the present invention includes: (a) a first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1) layer; and (b) second Al _Y1 In _Y2 Ga _1-Y1-Y2 N (0 ≦ Y1 <1) forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer. , 0 ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer, (c) a first electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer, and (d) the above And a second electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer, the first Al _X1 In _X2 Ga _1-X1-X2 N layer comprising the second Al _{Y1 in Y2 Ga 1-Y1-} Y2 N is on a layer, the first _Al X1 _in X2 Ga _-X1-X2 bandgap of N layer is greater than the band gap of the second _{Al Y1 In Y2 Ga 1-Y1} -Y2 N layer, a silicon of the first _{Al X1 In X2 Ga 1-X1} -X2 N layer The concentration is higher than the carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer, and the dislocation density of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N is 1 × 10 ⁸ cm ^−. less than ^2, the first electrode, forming a first _{Al X1 in X2 Ga 1-X1} -X2 N Schottky junction to layer.

The invention according to another aspect of the present invention is a group III nitride semiconductor epitaxial substrate for a group III nitride electronic device having a Schottky electrode, comprising: (a) a substrate; and (b) provided on the substrate. A first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1) layer; and (c) provided on the substrate, Second Al _Y1 In _Y2 Ga _1-Y1-Y2 N forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer (0 ≦ Y1 <1, 0 ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer, and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided between the first Al _X1 In _X2 Ga _1-X1-X2 N layer and the substrate. and it has the first _Al X1 _in X2 _{Ga 1-X1-} The band gap of ₂ N layer larger than the band gap of the second _{Al Y1 In Y2 Ga 1-Y1} -Y2 N layer, a silicon concentration in the first _{Al X1 In X2 Ga 1-X1} -X2 N layer is said The dislocation density of the second Al _Y1 In _{Y2Ga1 -Y1-Y2N} is less than 1 × 10 ⁸ cm ⁻² , which is larger than the carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer. is there.

Since carbon works to trap carriers in the gallium nitride semiconductor, leakage current is reduced in the gallium nitride semiconductor to which carbon is added. Therefore, carbon addition has been used to reduce leakage current. In addition, since silicon works to provide carriers in the gallium nitride semiconductor, the resistivity of the gallium nitride semiconductor decreases in the gallium nitride semiconductor to which silicon is added. Therefore, in a gallium nitride semiconductor with a high dislocation density, a large leakage current is generated by carriers from silicon. On the other hand, according to the group III nitride electronic device and the group III nitride semiconductor epitaxial substrate, the dislocation density of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is 1 × 10 ⁸ cm ⁻² . The leakage current due to dislocation is sufficiently low. Therefore, even if the silicon concentration is made higher than the carbon concentration in the first Al _X1 In _X2 Ga _1-X1-X2 N layer, the increase in leakage current is small. Also, current collapse due to carbon electron capture is reduced by silicon having a concentration higher than the carbon concentration.

In the group III nitride electronic device and the group III nitride semiconductor substrate product according to the above aspect of the present invention, the carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is 1 × 10 ¹⁷ cm ^−. It is preferably ³ or more.

According to the above group III nitride electronic device and group III nitride semiconductor substrate product, in the first Al _X1 In _X2 Ga _1-X1-X2 N layer having a carbon concentration of 1 × 10 ¹⁷ cm ⁻³ or more, Many electron capture levels resulting from carbon atoms are formed, and the leakage current is reduced. By adjusting the addition of silicon at a concentration higher than the carbon concentration, the leakage current and the like in the first Al _X1 In _X2 Ga _1-X1-X2 N layer are adjusted. As a result, current collapse due to electron capture is reduced by silicon having a concentration higher than the carbon concentration.

In the group III nitride electronic device of the present invention, the first Al _X1 In _X2 Ga _1-X1-X2 N layer is an AlGaN barrier layer, the group III nitride electronic device is a heterojunction transistor, The first electrode is a gate electrode of the heterojunction transistor, the second electrode is a drain electrode of the transistor, and the group III nitride electronic device includes the first Al _X1 In _X2 Ga _1-X1- further comprising a source electrode provided on the _{X2 N} layer. According to this group III nitride electronic device, current collapse can be reduced in a heterojunction transistor while avoiding a large increase in leakage current.

In the Group III nitride semiconductor substrate product of the present invention, the first Al _X1 In _X2 Ga _1-X1-X2 N layer is an AlGaN barrier layer, and the Group III nitride electronic device is a transistor having a heterojunction. And the Schottky electrode is a gate electrode of the transistor. According to this group III nitride semiconductor epitaxial substrate, a heterojunction transistor capable of reducing current collapse while avoiding a large increase in leakage current can be produced.

In the Group III nitride electronic device and Group III nitride semiconductor substrate product of the present invention, the first Al _X1 In _X2 Ga _1-X1-X2 N layer is an AlGaN layer, and the Group III nitride electronic device is It is a Schottky barrier diode, the first electrode is an anode electrode of the Schottky barrier diode, and the second electrode is a cathode electrode of the Schottky barrier diode. According to this group III nitride electronic device, current collapse can be reduced in the Schottky barrier diode while avoiding a large increase in leakage current. In addition, according to the group III nitride semiconductor epitaxial substrate, it is possible to manufacture a Schottky barrier diode capable of reducing current collapse while avoiding a large increase in leakage current.

In the group III nitride electronic device and group III nitride semiconductor substrate product according to the above aspect of the present invention, the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N layer is preferably made of GaN. According to the group III nitride electronic device and the group III nitride semiconductor substrate product, a good quality GaN crystal can be grown, so that the leakage current can be reduced.

The group III nitride electronic device and group III nitride semiconductor substrate product according to the above aspect of the present invention may further include a GaN substrate having a dislocation density of 1 × 10 ⁸ cm ⁻² or less. The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided on the GaN substrate, and the first Al _X1 In _X2 Ga _1-X1-X2 N layer is the second Al _Y1. It is preferably provided on the In _{Y2Ga1 -Y1-Y2N} layer. In the group III nitride electronic device and the group III nitride semiconductor substrate product, since the dislocation density of the GaN substrate is small, the leakage current due to the dislocation is reduced, but the current collapse can be reduced.

  In the group III nitride electronic device and the group III nitride semiconductor substrate product according to the above aspect of the present invention, the GaN substrate may be semi-insulating. The group III nitride electronic device and the group III nitride semiconductor substrate product provide an electronic device having good high frequency characteristics.

The group III nitride electronic device and the group III nitride semiconductor substrate product according to the above aspect of the present invention may further include a GaN template having a dislocation density of 1 × 10 ⁸ cm ⁻² or less. The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided on the GaN template, and the first Al _X1 In _X2 Ga _1-X1-X2 N layer is the second Al _Y1. In _{Y2Ga1 -Y1-Y2N} layer is provided. According to the group III nitride electronic device and the group III nitride semiconductor substrate product, since the dislocation density of the GaN template is small, the leakage current due to the dislocation is reduced, but the current collapse can be reduced.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, a group III nitride electronic device with reduced current collapse and low loss is provided. The present invention also provides a group III nitride semiconductor epitaxial substrate suitable for a low-loss group III nitride electronic device.

FIG. 1A is a drawing partially showing a group III nitride semiconductor epitaxial substrate for a group III nitride electronic device having a Schottky electrode. FIG. 1B is a drawing schematically showing the structure of the III nitride heterojunction transistor according to the present embodiment. FIG. 2A is a drawing schematically showing the structure of the III nitride heterojunction transistor according to the present embodiment. FIG. 2B is a drawing schematically showing the structure of the III nitride heterojunction transistor according to the present embodiment. FIG. 3 shows the structure of the epitaxial substrate. FIG. 4 is a graph showing the relationship between leakage current density and current collapse with respect to carbon addition. FIG. 5 is a drawing showing a list of the relationship between the carbon concentration and the current collapse. FIG. 6 is a graph showing the relationship between carbon concentration and current collapse. FIG. 7 is a graph showing the relationship between dislocation density and leakage current density. FIG. 8 is a graph showing the relationship between leakage current density and current collapse with respect to silicon addition. FIG. 9 is a diagram showing a list of relationships between leakage current density and current collapse with respect to silicon addition.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of the group III nitride electronic device and the group III nitride semiconductor substrate product of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

FIG. 1A is a drawing showing the structure of a group III nitride electronic device according to the present embodiment. The group III nitride electronic device 11 includes a first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1) layer 13 (13a, 13b, 13c). ), A second Al _Y1 In _Y2 Ga _1-Y1-Y2 N (0 ≦ Y1 <1, 0 ≦ Y2 <1, 0 ≦ Y1 + Y2 <1) layer 15, a first electrode 17, a second And an electrode 19. The second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N layer 15 forms a heterojunction 21 with the first Al _X1 In _X2 Ga _{1 -X1-X2} N layer 13. The first electrode 17 forms a junction with the first _{Al X1 In X2 Ga 1-X1} -X2 N layer is provided on the 13, the first _{Al X1 In X2 Ga 1-X1} -X2 N layer 13 . The second electrode 19 forms a junction with the first _{Al X1 In X2 Ga 1-X1} -X2 N is provided on the layer and the first _{Al X1 In X2 Ga 1-X1} -X2 N layer 13 . The band gap of the first Al _X1 In _X2 Ga _{1 -X1-X2} N layer 13 is larger than the band gap of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N layer 15. The first electrode 17 forms a Schottky junction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13. The first Al _X1 In _X2 Ga _{1 -X 1 -X 2} N layer 13 and the second Al _{Y 1} In _{Y 2} Ga ₁ -Y _{1 -Y 2} N layer 15 are provided on the substrate 23.

  FIG. 1 (a) also partially shows a group III nitride semiconductor epitaxial substrate for a group III nitride electronic device having a Schottky electrode, and an electrode 17 for the group III nitride electronic device 11, 19 is provided on the main surface of the group III nitride semiconductor epitaxial substrate E1.

In a preferred embodiment, the III-nitride electronic device 11 is, for example, a heterojunction transistor and a Schottky barrier diode. A reverse bias is applied to the first electrode 17 during a certain period during the operation of the group III nitride electronic device 11. On the other hand, in the operation of the group III nitride electronic device 11, the second electrode 19 provides carriers that flow to the group III nitride electronic device 11 during the operation period in which the forward bias is applied to the first electrode 17. Therefore, the second electrode 19 preferably forms an ohmic junction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13. Regarding the material, combinations of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13 and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer 15 include, for example, AlGaN / GaN, AlGaN / InGaN _{, Al X1 Ga 1-X1 N} / Al Y1 Ga 1-Y1 N (X1>Y1> 0), InAlN / GaN or the like is used. The first Al _X1 In _X2 Ga _1-X1-X2 N layer 13 and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer 15 are grown by, for example, metal organic chemical vapor deposition.

  When the group III nitride electronic device 11 is a heterojunction transistor, the first electrode 17 is a gate electrode, and the second electrode 19 is a source electrode and a drain electrode. Alternatively, when the group III nitride electronic device 11 is a Schottky barrier diode, the first electrode 17 is an anode electrode and the second electrode 19 is a cathode electrode. Each of these electronic devices is an electronic device in which a current flows through the surface layer of a gallium nitride based semiconductor layer, a so-called lateral electronic device. Therefore, the electrical characteristics of the group II nitride electronic device 11 are sensitive to charges trapped in the surface layer of the gallium nitride based semiconductor layer.

  Subsequently, a heterojunction transistor will be described as an example of the group III nitride electronic device according to the present embodiment with reference to FIGS. 1B, 2A, and 2B.

FIG. 1B is a drawing schematically showing a structure of a group III nitride heterojunction transistor according to the present embodiment. A group III nitride heterojunction transistor (referred to as a transistor) 11a includes a first Al _X1 In _X2 Ga _{1 -X1-X2} N layer 13 a and a second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N layer 15. And electrodes 17a, 18a, 19a. In the transistor 11a, a first Al _X1 In _X2 Ga _1-X1-X2 N layer 13a is used instead of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13. The carbon concentration N _C13 of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13a is less than 1 × 10 ¹⁷ cm ⁻³ . The dislocation density D of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N layer 15 is 1 × 10 ⁸ cm ⁻² . A two-dimensional electron gas layer 25 is generated by the heterojunction 21. The electrodes 17a, 18a, and 19a are a gate electrode, a source electrode, and a drain electrode, respectively. The array of the electrodes 17a, 18a, 19a is formed on the group III nitride semiconductor epitaxial substrate E2, and the group III nitride semiconductor epitaxial substrate E2 is formed of the first Al _X1 In _X2 Ga _1-X1-X2. The structure corresponding to the N layer 13a, the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer 15 and the substrate 23 is included.

Carbon forms a level for trapping carriers in a gallium nitride semiconductor. For this reason, the leakage current is small in the gallium nitride semiconductor to which carbon is added. Therefore, carbon addition has been used to reduce leakage current. On the other hand, according to the transistor 11a and the group III nitride semiconductor epitaxial substrate E2, the dislocation density of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer 15 is less than 1 × 10 ⁸ cm ⁻² . The leakage current due to dislocation is sufficiently low. Therefore, even if the carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13a grown thereon is lowered to less than about 1 × 10 ¹⁷ cm ⁻³ , the increase in leakage current is increased. Is small and acceptable. In the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13a, the carbon concentration N _C13 of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13a is less than 1 × 10 ¹⁷ cm ^−3. Therefore, the number of electron capture levels decreases. Although the electrons are captured by the trap level of the Al _X1 In _X2 Ga _1-X1-X2 N layer 13a near the gate by the voltage applied through the second electrode 18a, the number of captured electrons is , Thus reducing the effects of current collapse.

The substrate 23 has a threading dislocation density Tdd, and the dislocation density Tdd is preferably less than 1 × 10 ⁸ cm ⁻² , for example. As the substrate 23, GaN, AlN, AlGaN, InGaN or the like can be used.

FIG. 2A is a drawing schematically showing the structure of a group III nitride heterojunction transistor according to the present embodiment. The group III nitride heterojunction transistor 11b (hereinafter referred to as “transistor 11b”) includes a first Al _X1 In _X2 Ga _1-X1-X2 N layer 13b and a second Al _Y1 In _Y2 Ga _{1-Y1- A Y2N} layer 15 and electrodes 17a, 18a, 19a are provided. In the transistor 11b, the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13b is used instead of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13. The group III nitride semiconductor epitaxial substrate E3 includes components for the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13b, the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer 15 and the substrate 23. In addition, an array of electrodes 17a, 18a, 19a is formed on the main surface of group III nitride semiconductor epitaxial substrate E3. The silicon concentration N _Si13 of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13b is 1 × 10 ¹⁷ cm ⁻³ or more.

In gallium nitride based semiconductors, silicon serves to provide carriers. For this reason, the resistivity of a gallium nitride semiconductor decreases in a gallium nitride semiconductor to which silicon is added. Therefore, in a gallium nitride semiconductor with a high dislocation density, a large leakage current is generated by carriers from silicon. On the other hand, according to the group III nitride electronic device 11b and the group III nitride semiconductor epitaxial substrate E3, the dislocation density D of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N layer 15 is 1 × 10 ⁸ cm ^{−. 2,} so a sufficiently low leakage current due to the dislocation. Therefore, even if the silicon concentration _NSi13 of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13b _{grown thereon} is _increased to 1 × 10 ¹⁷ cm ⁻³ or more, the increase in leakage current is increased. Is small. In the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13b, the relaxation time of electrons trapped in the trap level is reduced. Electrons are trapped in the trap level near the gate of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13b by the voltage applied through the first and second electrodes 17a, 19a. However, since the silicon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13b is 1 × 10 ¹⁷ cm ⁻³ or higher, the trapped electrons are detrapped in a short time after the applied voltage disappears. Therefore, the influence of current collapse is reduced. Preferably, the silicon concentration N _Si13 is 1 × 10 ¹⁹ cm ⁻³ or less.

FIG. 2B is a drawing schematically showing the structure of the group III nitride heterojunction transistor according to the present embodiment. The group III nitride heterojunction transistor 11c (hereinafter referred to as “transistor 11c”) includes a first Al _X1 In _X2 Ga _1-X1-X2 N layer 13c and a second Al _Y1 In _Y2 Ga _{1-Y1- A Y2N} layer 15 and electrodes 17a, 18a, 19a are provided. In the transistor 11 c, the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13 is used instead of the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13. The group III nitride semiconductor epitaxial substrate E4 includes components for the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13c, the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer 15, and the substrate 23. In addition, an array of electrodes 17a, 18a, 19a is formed on the main surface of group III nitride semiconductor epitaxial substrate E4.

As already explained, carbon serves to trap carriers in the gallium nitride based semiconductor, and silicon serves to provide carriers in the gallium nitride based semiconductor. Carbon is added to the gallium nitride semiconductor, and carriers are trapped in the trap level due to the carbon, and current collapse is likely to occur, but on the other hand, since silicon higher than the carbon concentration is added, There are more carriers than the number of trap levels, and the resistivity decreases. Therefore, after the applied voltage disappears, the trapped electrons are detrapped in a short time, and therefore the influence of current collapse is reduced. Further, according to the transistor 11c and the group III nitride semiconductor epitaxial substrate E4, the dislocation density of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer 15 is 1 × 10 ⁸ cm ^−2. Leakage current due to is sufficiently low. Therefore, in the first Al _X1 In _X2 Ga _1-X1-X2 N layer 13c, even if the silicon concentration is higher than the carbon concentration, the increase in leakage current is small.

The relationship described above (the relationship between the current collapse and the carbon concentration) has been found by the inventors based on the following experiment.
(Experimental example)
Experiment 1:
An epitaxial substrate was fabricated on a (0001) -plane sapphire substrate using metal organic vapor phase epitaxy (MOVPE) as follows. Heat treatment in the furnace was performed for 5 minutes in a hydrogen atmosphere at 1050 degrees Celsius and an internal pressure of 100 torr (1 Torr is converted to 133.322 Pascals). After this, a low temperature GaN buffer layer (25 nm) was grown at 520 degrees Celsius. Next, a 2 μm non-doped GaN layer was grown under the conditions of 1050 degrees Celsius, furnace pressure of 100 torr and V / III = 1000. Subsequently, a non-doped Al _0.25 Ga _0.75 N layer was grown under conditions of 1070 degrees Celsius, 50 torr, and V / III = 500. Through these steps, an epitaxial substrate A-1 was produced. The dislocation density of the GaN layer by TEM evaluation was 2 × 10 ⁹ cm ⁻² .

Experiment 2:
Using the MOVPE method, an epitaxial substrate was produced on a 6H—SiC substrate as follows. In-furnace heat treatment was performed in a hydrogen atmosphere at 1050 degrees Celsius and a furnace pressure of 100 torr for 5 minutes. Thereafter, a non-doped Al _0.5 Ga _0.5 N buffer layer (100 nm) was grown at 1080 degrees Celsius. Next, a 2 μm non-doped GaN layer was grown under the conditions of 1050 degrees Celsius, furnace pressure of 100 torr and V / III = 1000. Subsequently, a non-doped 25 nm Al _0.25 Ga _0.75 N layer was grown under conditions of 1070 degrees Celsius, 50 torr and V / III = 500. Through these steps, an epitaxial substrate B-1 was produced. The dislocation density of the GaN layer by TEM evaluation was 5 × 10 ⁸ cm ⁻² .

Experiment 3:
Using the MOVPE method, the epitaxial substrate 31 shown in FIG. 3 was produced as follows. The surface of the high resistance GaN substrate 33 was subjected to a heat treatment in the furnace for 5 minutes at a temperature of 1000 degrees Celsius in an ammonia atmosphere. Thereafter, a non-doped GaN layer 35 of 2 μm was grown under the conditions of 1050 degrees Celsius, furnace pressure of 100 torr and V / III = 1000. Subsequently, a non-doped 25 nm Al _0.25 Ga _0.75 N layer 37 was grown under conditions of 1070 degrees Celsius, 50 torr, and V / III = 500. Through these steps, epitaxial substrates C-1 and D-1 were produced. According to TEM evaluation, the dislocation density of the GaN layer of the epitaxial substrate C-1 was 10 × 10 ⁷ cm ⁻² , and the dislocation density of the GaN layer of the epitaxial substrate D-1 was 10 × 10 ⁶ cm ⁻² .

  Similar to the above experiments, AlGaN layers were grown using various growth pressures. Epitaxial substrates A-2 to E-2 of 75 torr are produced as the growth pressure, epitaxial substrates A-3 to E-3 of 100 torr are produced as the growth pressure, and epitaxial substrates A-4 to E-4 of 150 torr are produced as the growth pressure. Then, epitaxial substrates A-5 to E-5 having a growth pressure of 200 torr were prepared.

  In order to evaluate leakage current Igs (gate-source current) and current collapse at the time of reverse bias, electrodes (gate electrode, source electrode and drain electrode) are formed on the epitaxial substrate, and a transistor having a HEMT structure is formed. Produced. The gate electrode has a ring shape with a gate width Wg = 0.5 mm and a drain-gate distance Lgd = 10 μm. The drain electrode is located in the ring, and the source electrode is provided so as to surround the ring.

  For the evaluation of the collapse state, the on-resistance is measured prior to the application of the reverse bias and the on-resistance is measured for 5 minutes and after the application of the voltage Vds = 100 volts. Later on-resistance / on-resistance before bias application). When there is no current collapse, the on-resistance ratio is 1. When there is a current collapse, the current collapse is greater than one. The leakage current is defined by Igs (gate-source current) when a voltage Vds = 100 volts is applied.

The results of these measurements are shown in FIG. FIG. 4 shows characteristic lines C1, C2, C3 and C4. FIG. 5 shows the measurement result shown in FIG. In FIG. 5, the carbon concentration is that of AlGaN on the GaN substrate. In FIG. 5, for example, at a growth pressure of 50 torr, the carbon concentration of AlGaN on the Sap substrate is 3.2 × 10 ¹⁸ cm ⁻³ , the leakage current is 2.2 × 10 ⁻⁹ A / mm, and the current collapse is Is 10.41. The Sap substrate indicates a sapphire substrate.

As shown in FIG. 4 and FIG. 5, a trade-off relationship between leakage current and current collapse is established regardless of the type of substrate. In FIG. 5, when the growth pressure is 150 torr, the carbon concentration is, for example, 9.7 × 10 ¹⁶ cm ⁻³ , and this value is less than 1.0 × 10 ¹⁷ cm ⁻³ . In this carbon range, good characteristics are obtained for both leakage current and current collapse in the HEMT structure on the low dislocation GaN substrate.

  Even if both substrates are used, the trade-off relationship between leakage current and collapse is established, but the leakage current of the epitaxial substrate of the sapphire substrate and SiC substrate used in this experiment is larger than that of the GaN substrate, and the carbon concentration is high. As it increases, the current collapse increases. On the other hand, the leakage current of the epitaxial substrate of the GaN substrate used in this experiment is small, and even if the carbon concentration is reduced in order to reduce current collapse, the increase in leakage current is in an acceptable range. That is, it is considered that the trade-off in this case can be partially alleviated with an epitaxial substrate using a low dislocation GaN substrate.

In the experiment, sapphire substrate, SiC substrate, and GaN substrate were used to realize various dislocation densities, and the relaxation of this trade-off is not intrinsically related to the type of substrate, but the buffer It is related to the dislocation density of the layer. A low dislocation GaN substrate is suitable for forming a low dislocation buffer layer. The low dislocation buffer layer provides a low dislocation underlayer for the AlGaN barrier layer. Therefore, a low dislocation AlN substrate or an AlN / sapphire template can also realize relaxation of trade-off (leakage current and current collapse trade-off) if the dislocation density is 1 × 10 ⁸ cm ⁻² or less.

  That is, in the HEMT structure on the low dislocation GaN substrate, for example, by increasing the growth pressure and reducing the carbon concentration, the leakage current slightly increases, but the increased leakage current does not exceed the allowable range. It is sufficiently low and current collapse can be reduced to a practical level. A practical current collapse level is shown as “Ref1” in FIG. The level Ref1 is, for example, about 1.3 in on-resistance ratio.

FIG. 6 is a drawing showing the relationship between carbon concentration and current collapse. FIG. 6 shows characteristic lines I1 to I4. In a device with a large current collapse, the on-resistance increases. For this reason, the current collapse value is preferably about 1.3 or less. “Ref2” in FIG. 6 indicates 1.3. Referring to FIG. 5, when the carbon concentration is less than 1 × 10 ¹⁷ cm ⁻³ , a practical current collapse is provided in the range of dislocation density of 2 × 10 ^{9 to} 5 × 10 ⁶ cm ⁻³ .

FIG. 7 is a drawing showing the relationship between dislocation density and leakage current density. FIG. 7 shows characteristic lines J1 to J5. The practical level of the leakage current density is 1 × 10 ⁻⁷ A / cm ² or less, and this value is referred to as “Ref 3” in FIG. As the carbon concentration decreases, the leakage current also decreases. However, taking into account the value of current collapse, the carbon concentration is preferably less than 1 × 10 ¹⁷ cm ⁻³ . When the carbon concentration is less than 1 × 10 ¹⁷ cm ⁻³ and the dislocation density is less than 1 × 10 ⁸ cm ⁻² , the leakage current density and current collapse are in a practical range.

  In the above experiment, the growth pressure is changed to change the carbon concentration. However, the carbon concentration can be reduced by changing the growth temperature, the ammonia flow rate, the V / III ratio, the growth rate, and the like. Regarding the growth temperature, the carbon concentration decreases as the temperature increases. Regarding the ammonia flow rate, increasing the flow rate reduces the carbon concentration. Regarding the V / III ratio, increasing the V / III ratio reduces the carbon concentration. Regarding the growth rate, the carbon concentration is reduced when the growth rate is lowered.

  The above experiment has explained the reduction of carbon in the barrier layer. Not only the reduction of the carbon concentration but also the silicon (Si) doping to the barrier layer, the same result as the effect was obtained by the reduction of the carbon.

Epitaxial substrates were fabricated by changing the silicon concentration. Under the conditions of epitaxial substrates A-3, B-3, C-3, and D-3 (AlGaN growth pressure is 100 torr) as production conditions, the silicon concentration in the AlGaN layer is 3.1 × 10 ¹⁶ cm ⁻³ , and 1. 1 × 10 ¹⁷ cm ⁻³ and 3.7 × 10 ¹⁷ cm ⁻³ were added. The collapsed state and the leakage current were evaluated for these epitaxial substrates.

The results of these measurements are shown in FIG. FIG. 8 shows characteristic lines S1, S2, S3, and S4. A list of results shown in FIG. 8 is shown in FIG. In FIG. 9, the Si concentration is that of AlGaN on the GaN substrate. 9, for example, the growth pressure 100 torr, the carbon concentration of AlGaN of Sap substrate is 3.4 × ¹⁰ 17 ^{cm -3,} Si concentration was 3.1 × ¹⁰ 16 ^{cm -3,} the leakage current is 3 .9 × 10 ⁻⁶ A / mm and the current collapse is 1.36. Regardless of the silicon concentration, a carbon concentration of 3.4 × 10 ¹⁷ cm ⁻³ was used.

As shown in FIG. 8, there is a trade-off relationship between leakage current and collapse regardless of the type of substrate. In FIG. 9, when the growth pressure is 100 torr, the Si concentration is, for example, 1.1 × 10 ¹⁷ cm ⁻³ , and is 1.0 × 10 ¹⁷ cm ⁻³ or more. Within this Si concentration range, good characteristics are obtained for both leakage current and current collapse in the HEMT structure on the low dislocation GaN substrate.

From another viewpoint, when the silicon concentration is equal to or higher than the carbon concentration, good characteristics are obtained in both the leakage current and the current collapse in the low dislocation GaN substrate HEMT structure. With the addition of Si to AlGaN, a large dislocation density of AlGaN (for example, AlGaN formed on a sapphire substrate or SiC substrate) causes a significant increase in leakage current as the collapse is reduced. However, in AlGaN having a low dislocation density (AlGaN formed on a low dislocation GaN substrate), the increase in leakage current due to the addition of Si is sufficiently low, and the current collapse can be significantly reduced. When adding both carbon and Si, the following concentration ranges are used. The carbon concentration is preferably 3 × 10 ¹⁶ cm ⁻³ or more. This is because it is difficult to lower the carbon concentration below that. The carbon concentration is preferably 1 × 10 ¹⁹ cm ⁻³ or less. This is because a good epitaxial film cannot be obtained. The Si concentration is preferably 3 × 10 ¹⁶ cm ⁻³ or more. This is because it is difficult to make the carbon concentration 3 × 10 ¹⁶ cm ⁻³ or less. The Si concentration is preferably 1 × 10 ¹⁹ cm ⁻³ or less. This is because the leakage current increases if the Si concentration is too high.

Further, the same effect as the effect according to the present embodiment can be obtained by reducing the carbon in the buffer layer (for example, the GaN buffer layer). Specifically, it is effective in reducing current collapse. In this embodiment, the HEMT structure has been described. The present invention is not limited to the embodiment described in the embodiment, and the same effect can be obtained with a lateral electronic device such as a lateral Schottky barrier diode.
As described above, according to the present embodiment, a current collapse is reduced and a low-loss group III nitride electronic device is provided. The present invention also provides a group III nitride semiconductor epitaxial substrate suitable for a low-loss group III nitride electronic device.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

Conventionally, when producing an epitaxial film for a HEMT structure on a GaN substrate, conditions for producing an epitaxial film for a HEMT structure on a sapphire substrate have been used. Since the conditions in which the carbon concentration is 3 × 10 ¹⁷ cm ⁻³ or more are used as they are for the growth in the GaN substrate, the leakage current density is extremely small, but the current collapse is larger than that of the HEMT structure on the sapphire substrate.

However, as described above, by setting the carbon concentration in AlGaN to less than 1 × 10 ¹⁷ cm ⁻³ , current collapse and current leakage can be simultaneously reduced. Further, by setting the silicon concentration in AlGaN to 1 × 10 ¹⁷ cm ⁻³ or more, current collapse and current leakage can be simultaneously reduced. Furthermore, by making the silicon concentration in AlGaN larger than the carbon concentration, current collapse and current leakage can be simultaneously reduced. That is, by using a low dislocation base semiconductor region, growth conditions that increase the leakage current can be used, and the trade-off relationship between the leakage current and current collapse is partially overcome to reduce the leakage. Current and current collapse can be substantially suppressed.

11, 11a, 11b, 11c ... Group III nitride electronic device, 13, 13a, 13b, 13c ... First Al _X1 In _X2 Ga _1-X1-X2 N layer, 15 ... Second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer, 17 ... first electrode, 19 ... second electrode, 17a, 18a, 19a ... electrode, 21 ... heterojunction, 23 ... substrate, 25 ... two-dimensional electron gas layer, 31 ... epitaxial Substrate, 33 ... high resistance GaN substrate, 35 ... non-doped GaN layer, 37 ... Al _0.25 Ga _0.75 N layer, E1, E2, E3, E4 ... group III nitride semiconductor epitaxial substrate, N _Si13 ... silicon concentration

Claims (9)

A first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1) layer;
Second Al _Y1 In _Y2 Ga _1-Y1-Y2 N (0 ≦ Y1 <1, 0 ≦ Y2 <1, 0 ≦ 0) forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer Y1 + Y2 <1)
Layers,
A first electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer;
A second electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer;
With a substrate,
The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided on the substrate;
The substrate, GaN substrate having a dislocation density of 1 × ¹⁰ 8 ^{cm -2} or less, AlN substrate having a dislocation density of 1 × ¹⁰ 8 ^{cm -2} or less, 1 × ¹⁰ 8 ^{cm -2} AlGaN having the dislocation density substrate, is either 1 × ¹⁰ 8 ^{cm -2} InGaN substrate having the dislocation density, and 1 × ¹⁰ 8 ^{cm -2} GaN template having the following dislocation density,
The first Al _X1 In _X2 Ga _1-X1-X2 N layer is on the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer;
The band gap of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is larger than the band gap of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer,
A two-dimensional electron gas layer is generated at the heterojunction of the first Al _X1 In _X2 Ga _1-X1-X2 N layer and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer;
The first Al _X1 In _X2 Ga _1-X1-X2 N layer is non-doped,
The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is non-doped,
The carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is less than 1 × 10 ¹⁷ cm ⁻³ ;
The dislocation density of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N layer is less than 1 × 10 ⁸ cm ⁻² ;
The group III nitride electronic device, wherein the first electrode forms a Schottky junction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer. A first Al _X1 In _X2 Ga _1-X1-X2 N (0 <X1 <1, 0 ≦ X2 <1, 0 <X1 + X2 <1) layer;
Second Al _Y1 In _Y2 Ga _1-Y1-Y2 N (0 ≦ Y1 <1, 0 ≦ Y2 <1, 0 ≦ 0) forming a heterojunction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer Y1 + Y2 <1) layer;
A first electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer;
A second electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer;
With a substrate,
The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided on the substrate;
The substrate, GaN substrate having a dislocation density of 1 × ¹⁰ 8 ^{cm -2} or less, AlN substrate having a dislocation density of 1 × ¹⁰ 8 ^{cm -2} or less, 1 × ¹⁰ 8 ^{cm -2} AlGaN having the dislocation density substrate, is either 1 × ¹⁰ 8 ^{cm -2} InGaN substrate having the dislocation density, and 1 × ¹⁰ 8 ^{cm -2} GaN template having the following dislocation density,
The first Al _X1 In _X2 Ga _1-X1-X2 N layer is on the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer;
The band gap of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is larger than the band gap of the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer,
Greater than the carbon concentration of the first _{Al X1 In X2 Ga 1-X1} -X2 silicon concentration N layer is the first _{Al X1 In X2 Ga 1-X1} -X2 N layer,
A two-dimensional electron gas layer is generated at the heterojunction of the first Al _X1 In _X2 Ga _1-X1-X2 N layer and the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer;
The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is non-doped,
The carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is 3 × 10 ¹⁶ cm ⁻³ or more,
The carbon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is 1 × 10 ¹⁹ cm ⁻³ or less,
The silicon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is 1 × 10 ¹⁷ cm ⁻³ or more,
The silicon concentration of the first Al _X1 In _X2 Ga _1-X1-X2 N layer is 1 × 10 ¹⁹ cm ⁻³ or less,
The dislocation density of the second Al _Y1 In _Y2 Ga _{1 -Y1-Y2} N is less than 1 × 10 ⁸ cm ⁻² ;
The group III nitride electronic device, wherein the first electrode forms a Schottky junction with the first Al _X1 In _X2 Ga _1-X1-X2 N layer. The leakage current density when a reverse bias of 100 volts is applied between the first electrode and the second electrode is 1 × 10 ⁻⁷ A / cm ² or less. Or a group III nitride electronic device according to claim 2. The first Al _X1 In _X2 Ga _1-X1-X2 N layer is an AlGaN barrier layer;
The group III nitride electronic device is a heterojunction transistor,
The first electrode is a gate electrode of the heterojunction transistor;
The second electrode is a drain electrode of the heterojunction transistor;
The group III nitride electronic device further comprises a source electrode provided on the first Al _X1 In _X2 Ga _1-X1-X2 N layer. A group III nitride electronic device according to claim 1. 5. The group III nitride electronic device according to claim 4, wherein the second Al _Y1 In _Y2 Ga ₁ -Y _{1 -Y 2} N layer is made of GaN. The first Al _X1 In _X2 Ga _1-X1-X2 N layer is an AlGaN layer;
The group III nitride electronic device is a Schottky barrier diode,
The first electrode is an anode electrode of the Schottky barrier diode;
The group III nitride electronic device according to any one of claims 1 to 3, wherein the second electrode is a cathode electrode of the Schottky barrier diode.   The group III nitride electronic device according to any one of claims 1 to 6, wherein the substrate is the GaN substrate.   8. The group III nitride electronic device according to claim 7, wherein the GaN substrate is semi-insulating. The substrate is the GaN template;
The second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer is provided on the GaN template;
The first Al _X1 In _X2 Ga _1-X1-X2 N layer is provided on the second Al _Y1 In _Y2 Ga _1-Y1-Y2 N layer. The group III nitride electronic device according to any one of items 6.

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