KR102170211B1 - Power semiconductor device and Power semiconductor circuit including the device - Google Patents

Abstract

The power semiconductor device of the embodiment is disposed between a cathode, a first nitride semiconductor layer on the cathode, an anode on the first nitride semiconductor layer, and between the first nitride semiconductor layer and the anode, and the content ratio of the first component among the components is first And a second nitride semiconductor layer increasing from the nitride semiconductor layer toward the anode.

Description

Power semiconductor device and power semiconductor circuit including the same

The embodiment relates to a power semiconductor device and a power semiconductor circuit including the same.

In general, diodes used in circuits suitable for high voltage switching operate in the reverse direction, that is, when the voltage at the cathode is higher than the voltage at the anode, the reverse leakage current should be as small as possible and can withstand high voltages, such as at least 600 or 1200 volts Should be.

Power semiconductor devices such as a Schottky barrier diode (SBD), which is a kind of diode, are used as a key component of a switch-mode power supply (SMPS) together with a transistor. This is because SBD has excellent switching speed and on-state performance.

GaN has advantageous physical properties that can be applied to power semiconductor devices such as a wide bandgap, a two-dimensional electron gas (2DEG) channel, high mobility, and a high critical electric field. SBD implemented using a semiconductor such as GaN has a high breakdown voltage of 600 V or more and a low threshold voltage of 1 volt or less, and exhibits stable switching characteristics even at high temperatures, as well as a commercially available silicon (Si) high recovery diode (FRD: Fast Recovery Diode) and SiC SBD.

1A is a cross-sectional view of an existing power semiconductor device 10A, and FIG. 1B is a graph showing current-voltage characteristics of the power semiconductor device 10A shown in FIG. 1A.

The conventional power semiconductor device 10A shown in FIG. 1A is a type of SBD, and includes an ohmic electrode 5, an n+ GaN layer 7, an n-GaN layer 9, and a Schottky electrode 11.

The Schottky electrode 11 is formed directly on the n-GaN layer 9. Therefore, under the reverse bias condition, a strong electric field is generated at the boundary between the Schottky electrode 11 and the n-GaN layer 9, resulting in a large reverse bias leakage current (or reverse bias) as indicated by the arrow 22 in FIG. Direction leakage current) flows.

2A is a cross-sectional view of another conventional power semiconductor device 10B, and FIG. 2B is a graph showing current-voltage characteristics of the power semiconductor device 10B illustrated in FIG. 2A.

The other conventional power semiconductor device 10B shown in FIG. 2A is a kind of SBD, and an ohmic electrode 5, an n+ GaN layer 7, an n-GaN layer 9, a Schottky electrode 11, and an InGaN layer ( 13). Here, the content ratio of In and Ga in the InGaN layer 13 is a fixed value that does not change from the boundary with the n+ GaN layer 7 to the boundary with the Schottky electrode 11.

Unlike the power semiconductor device 10A shown in FIG. 1A, in the case of the power semiconductor device 10B shown in FIG. 2A, the InGaN layer 13 is disposed between the Schottky electrode 11 and the n-GaN layer 9 do. Accordingly, compared with the power semiconductor device 10A of FIG. 1A, the reverse bias leakage current is substantially reduced as indicated by the arrow 24 in FIG. 2B. However, under the forward bias condition, since the turn-on voltage increases as indicated by the arrow 26 in FIG. 2B, there is a problem that the forward current decreases. That is, there is a problem in that the turn-on voltage Vf2 shown in FIG. 2B becomes larger than the turn-on voltage Vf1 shown in FIG. 1B.

The embodiment provides a power semiconductor device in which a forward bias turn-on voltage does not increase while reducing a reverse bias leakage current, and a power semiconductor circuit including the same.

A power semiconductor device according to an embodiment includes a cathode; A first nitride semiconductor layer over the cathode; An anode over the first nitride semiconductor layer; And a second nitride semiconductor layer disposed between the first nitride semiconductor layer and the anode, wherein a content ratio of the first component among the components increases from the first nitride semiconductor layer toward the anode.

Components of the first nitride semiconductor layer and the second nitride semiconductor layer may be different from each other. In this case, the first nitride semiconductor layer may include GaN, the second nitride semiconductor layer may include In as the first component and GaN as the second component.

Alternatively, components of the first nitride semiconductor layer and the second nitride semiconductor layer may be the same. In this case, the first nitride semiconductor layer may contain AlGaN, and the second nitride semiconductor layer may contain Al as the first constituent and GaN as the second constituent.

The content ratio of the first component may be greater than 0 and less than 0.2.

The content ratio of the first component may increase linearly, increase in a stepwise manner, or increase in a parabolic shape.

The second nitride semiconductor layer may include at least one first sub-nitride semiconductor layer including the first component; And at least one second sub-nitride semiconductor layer not including the first component.

At least one of the at least one first sub-nitride semiconductor layer or the at least one second sub-nitride semiconductor layer may be a plurality, and the first and second sub-nitride semiconductor layers may be alternately and repeatedly disposed.

The content ratio of the first constituents of the plurality of first sub-nitride semiconductor layers may be smaller as they are disposed closer to the first nitride semiconductor layer, and may be greater as they are disposed closer to the anode. The first and second sub-nitride semiconductor layers may have a uniform thickness.

Alternatively, the thickness of the plurality of first sub-nitride semiconductor layers may be thinner when disposed closer to the first nitride semiconductor layer, and thicker when disposed closer to the anode. The thickness of the second sub-nitride semiconductor layer disposed between the first sub-nitride semiconductor layers may be constant.

Alternatively, the thickness of the plurality of first sub-nitride semiconductor layers is constant, and the thickness of the second sub-nitride semiconductor layer disposed between the first sub-nitride semiconductor layers is thicker as it approaches the first nitride semiconductor layer. The closer to the anode, the thinner it can be.

The content ratio of the first component in the plurality of first sub-nitride semiconductor layers may be uniform.

The average value of the content ratio of the first component in the plurality of first and second sub-nitride semiconductor layers may increase from the first nitride semiconductor layer toward the anode.

At least one of the at least one first sub-nitride semiconductor layer or the at least one second sub-nitride semiconductor layer may be a superlattice layer.

Alternatively, the second nitride semiconductor layer includes a plurality of sub-nitride semiconductor layers each including the first component, and the content ratio of the first component of the plurality of sub-nitride semiconductor layers is the first The closer to the nitride semiconductor layer, the smaller and the closer to the anode, the larger may be. Each of the plurality of sub-nitride semiconductor layers may be a super lattice layer.

A power semiconductor circuit according to another embodiment may include the power semiconductor device; And a passive device electrically connected to the power semiconductor device.

The power semiconductor device according to the embodiment and the power semiconductor circuit including the same are disposed between the first nitride semiconductor layer and the anode, and include a second component having a content ratio increasing from the first nitride semiconductor layer to the anode. By having the nitride semiconductor layer, the reverse bias current can be reduced and the forward bias turn-on voltage can be lowered.

1A is a cross-sectional view of a conventional power semiconductor device, and FIG. 1B is a graph showing current-voltage characteristics of the power semiconductor device shown in FIG. 1A.
FIG. 2A is a cross-sectional view of another conventional power semiconductor device, and FIG. 2B is a graph showing current-voltage characteristics of the power semiconductor device shown in FIG. 2A.
3 is a cross-sectional view of a power semiconductor device according to an embodiment.
FIG. 4 is a cross-sectional view illustrating an embodiment of the 1-2 nitride semiconductor layer and the second nitride semiconductor layer illustrated in FIG. 3.
5 is a cross-sectional view showing another embodiment of the 1-2 nitride semiconductor layer and the second nitride semiconductor layer illustrated in FIG. 3.
6A to 6C are graphs showing changes in the content ratio of the first component included in the second nitride semiconductor layer.
7 is a cross-sectional view of another embodiment of the second nitride semiconductor layer illustrated in FIG. 3.
FIG. 8 is a diagram illustrating a change in thickness of first and second sub-nitride semiconductor layers in a second nitride semiconductor layer.
9 is a diagram of another embodiment showing thickness changes of first and second sub-nitride semiconductor layers in a second nitride semiconductor layer.
10A and 10B show energy band diagrams when the conventional power semiconductor device shown in FIG. 1A is reverse biased and forward biased, respectively.
11A and 11B show energy band diagrams when the conventional power semiconductor device shown in FIG. 2A is reverse biased and forward biased, respectively.
12A and 12B show energy band diagrams when the power semiconductor device of the embodiment shown in FIG. 3 is reverse biased and forward biased, respectively.
13 is a graph showing a comparison of the forward bias current-voltage characteristics of the conventional power semiconductor device and the power semiconductor device according to the present embodiment.
14A to 14C are graphs comparing energy bands in a situation in which the power semiconductor device is reverse biased.
15 is a graph showing a comparison of the reverse bias current-voltage characteristics of the conventional power semiconductor device and the power semiconductor device according to the present embodiment.
16 is a circuit diagram of a power semiconductor device according to an embodiment.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings in order to explain the present invention by way of example, and to aid understanding of the invention. However, the embodiments according to the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more completely describe the present invention to those with average knowledge in the art.

In the description of the present embodiment, in the case of being described as being formed in "on or under" of each element, upper (upper) or lower (lower) ( On or under includes both elements in which two elements are in direct contact with each other or one or more other elements are indirectly formed between the two elements.

In addition, when expressed as “up (up)” or “on or under”, it may include not only an upward direction but also a downward direction based on one element.

In addition, relational terms such as "first" and "second," "upper" and "lower" used below do not necessarily require or imply any physical or logical relationship or order between such entities or elements. Thus, it may be used only to distinguish one entity or element from another entity or element.

3 is a cross-sectional view of a power semiconductor device 100 according to an embodiment.

The power semiconductor device 100 illustrated in FIG. 3 is a kind of Schottky Barrier Diode (SBD) and includes a cathode 110, an anode 120, a first nitride semiconductor layer 130, and a second nitride semiconductor layer 140. .

A first nitride semiconductor layer 130 is disposed on the cathode 110.

The cathode 110 may include a material that makes ohmic contact with the first nitride semiconductor layer 130, and may include aluminum (Al), titanium (Ti), chromium (Cr), nickel (Ni), and copper ( It may be formed in a single layer or multilayer structure including at least one of Cu) or gold (Au). For example, the cathode 110 may be implemented in a double layer structure of Ti/Au.

The first nitride semiconductor layer 130 may include at least one of the 1-1 nitride semiconductor layer 132 and the 1-2 nitride semiconductor layer 134. In the case of FIG. 3, the first nitride semiconductor layer 130 is illustrated as including all of the 1-1 and 1-2 nitride semiconductor layers 132 and 134, but embodiments are not limited thereto.

The first-first nitride semiconductor layer 132 is disposed on the cathode 110, and the first-second nitride semiconductor layer 134 is disposed on the first-first nitride semiconductor layer 132. Each of the 1-1 nitride semiconductor layer 132 and the 1-2 nitride semiconductor layer 134 is Al _a In _b Ga _(1-ab) N (0≤a≤1, 0≤b≤1, 0≤a) It may be formed of a semiconductor material having a composition formula of +b≤1).

Each of the first-first nitride semiconductor layer 132 and the first-second nitride semiconductor layer 134 may be of a first conductivity type. If each of the 1-1 and 1-2 nitride semiconductor layers 132 and 134 is an n-type semiconductor layer, the first conductivity-type dopant includes an n-type dopant such as P (phosphorus) or As (arsenic). can do. In addition, each of the 1-1 and 1-2 nitride semiconductor layers 132 and 134 may be formed as a single layer or a multilayer, but is not limited thereto.

The doping concentration of the first conductivity type dopant in the 1-1 nitride semiconductor layer 132 may be higher than the doping concentration of the first conductivity type dopant in the 1-2nd nitride semiconductor layer 134. For example, the doping concentration of the 1-2 nitride semiconductor layer 134 may be 3 x 10 ¹⁶ atoms/cm 3, and the thickness of the 1-2 nitride semiconductor layer 134 may be 5 μm. Is not limited to the doping concentration and thickness of each of these layers 132 and 134.

The anode 120 is disposed on the second nitride semiconductor layer 140.

The anode 120 may include a material capable of Schottky bonding with the second nitride semiconductor layer 140. The anode 120 may include at least one of a first layer or a second layer disposed on the first layer. Here, the first layer may include a refractory metal and a material having a high work function or a mixture of refractory metals. For example, the first layer is Ni (Nickel), TiN (Titanium Nitride), WN (Tungsten Nitride), WSi _X (Tungsten Silicide) (where X is a natural number), W (Tungsten), Pt (Platinum), Au (Aurum), Cr (Chromium), Mo (Molybdenum), or Ag (Argentum) may contain at least one material, the second layer may contain Au. For example, the anode 120 may have a Ni/Au double layer structure.

Meanwhile, the second nitride semiconductor layer 140 is disposed between the first nitride semiconductor layer 130 and the anode 120. The second nitride semiconductor layer 140 may have a plurality of constituent components. The content ratio (or mole fraction) of the first component among the plurality of components increases from the first nitride semiconductor layer 130 to the anode 120. In addition, the second nitride semiconductor layer 140 may have a very thin thickness, for example, may have a thickness of 3 nm.

The constituent components of the second nitride semiconductor layer 140 are as follows.

4 is a cross-sectional view illustrating an embodiment of the 1-2 nitride semiconductor layer 134 and the second nitride semiconductor layer 140 illustrated in FIG. 3.

5 is a cross-sectional view illustrating another embodiment of the 1-2 nitride semiconductor layer 134 and the second nitride semiconductor layer 140 illustrated in FIG. 3.

According to an embodiment, the components of the second nitride semiconductor layer 140 may be different from those of the first nitride semiconductor layer 130. For example, as illustrated in FIG. 4, the 1-2nd nitride semiconductor layer 134 includes GaN. However, the second nitride semiconductor layer 140A may contain In as a first constituent and GaN as a second constituent. That is, the second nitride semiconductor layer 140A may be implemented as In _X GaN _(1-X) N. Here, the content ratio X of In, which is the first component of the second nitride semiconductor layer 140A, may be greater than 0 and less than 0.2. For example, the content ratio (X) of In may be 0.02 to 0.1.

According to another embodiment, the components of the second nitride semiconductor layer 140 may be the same as those of the first nitride semiconductor layer 130. For example, as illustrated in FIG. 5, the first nitride semiconductor layer 130 includes AlGaN, the second nitride semiconductor layer 140B includes Al as a first constituent, and GaN is a second constituent. It can be included as. That is, the 1-2nd nitride semiconductor layer 134B may be implemented as AlGaN, and the second nitride semiconductor layer 140B may be implemented as Al _Y Ga _(1-Y) N. Here, the content ratio of Al in AlGaN of the 1-2nd nitride semiconductor layer 134B is, for example, 0.25, and the content ratio of Ga is, for example, 0.75, which may be a fixed value. However, the content ratio Y of Al, which is the first component of the second nitride semiconductor layer 140B, may increase from the first nitride semiconductor layer 130 to the anode 120. The content ratio (Y) of Al is greater than 0 and less than 0.2, and, for example, the content ratio (Y) of Al may be 0.05 to 0.1.

As described above, the content ratio (eg, X, Y) of the first constituents (eg, In, Al) illustrated in FIGS. 4 and 5 increases from the first boundary (I1) to the second boundary (I2). Can increase. Here, the first boundary I1 means a boundary between the first nitride semiconductor layer 130 and the second nitride semiconductor layer 140, and the second boundary I2 is the second nitride semiconductor layer 140 and the anode ( 120), but is not limited to this.

In addition, the constituent components of the second nitride semiconductor layer 140 are not limited to the materials illustrated with reference to FIGS. 4 and 5 described above. According to Poisson's equation, the negative polarization charge in the second nitride semiconductor layer 140 becomes more negative as the electric field goes from the second boundary I2 toward the first boundary I1. Make it possible. The polarization charge is caused because spontaneous polarization and piezoelectric polarization depend on the content ratio of the first component included in the second nitride semiconductor layer 140. In consideration of this, the constituent component of the second nitride semiconductor layer 140 may include any material as long as it may cause negative polarization charges in the second nitride semiconductor layer 140. That is, any material that can cause negative polarization charge in the second nitride semiconductor layer 140 so that the electric field becomes more negative as it goes from the second boundary I2 toward the first boundary I1. 2 It may be a component of the nitride semiconductor layer 140.

6A to 6C are graphs showing a change in the content ratio of the first component included in the second nitride semiconductor layer 140. Here, Z represents the distance from the first boundary I1 to the second boundary I2. That is, Z=0 at the first boundary I1.

According to an embodiment, the content ratio (eg, X, Y) of the first component (eg, In, Al) included in the second nitride semiconductor layer 140 is monotonic as illustrated in FIG. 6A. ) Can increase linearly.

According to another embodiment, the content ratio (eg, X, Y) of the first component (eg, In, Al) included in the second nitride semiconductor layer 140 is piecewise as illustrated in FIG. 6B. ) Can be increased in steps.

According to another embodiment, the content ratio (eg, X, Y) of the first component (eg, In, Al) included in the second nitride semiconductor layer 140 is parabolic as illustrated in FIG. 6C. ) Can also be increased.

7 is a cross-sectional view of another embodiment 140C of the second nitride semiconductor layer 140 illustrated in FIG. 3.

As illustrated in FIG. 7, the second nitride semiconductor layer 140C includes a plurality of sub nitride semiconductor layers 140C-1, 140C-2, 140C-3, ..., 140C-(N-2), 140C- (N-1), 140C-N) may be included. Here, N is a positive integer of 2 or more. Here, each of the plurality of sub-nitride semiconductor layers may be a super lattice layer (SL), but embodiments are not limited thereto.

According to an embodiment, each of the plurality of sub-nitride semiconductor layers may include a first component (eg, In, Al). That is, the content ratio (eg, X, Y) of the first component (eg, In, Al) included in each of the plurality of sub-nitride semiconductor layers may not be zero. In this case, the content ratio of the first constituent components of the plurality of sub-nitride semiconductor layers is smaller as it is closer to the first nitride semiconductor layer 130 (ie, the first boundary I1), and the anode 120 (ie, the second boundary The closer to (I2)), the larger it can be. That is, the content ratio of the first component of the plurality of sub-nitride semiconductor layers may increase from the first boundary I1 to the second boundary I2.

According to another embodiment, the plurality of sub-nitride semiconductor layers 140C-1, 140C-2, 140C-3, ..., 140C-(N-2), 140C-(N-1), 140C-N) are It may include at least one first sub-nitride semiconductor layer and at least one second sub-nitride semiconductor layer. Here, the first sub-nitride semiconductor layer refers to a layer containing a first component (eg, In, Al) (eg, a layer in which X or Y is not 0), and the second sub-nitride semiconductor layer is 1 It refers to a layer (eg, a layer in which X or Y is 0) that does not contain a component (eg, In, Al).

At least one of the first sub-nitride semiconductor layer and the second sub-nitride semiconductor layer may be plural. In this case, the plurality of first and second sub-nitride semiconductor layers may be alternately and repeatedly disposed. For example, the first sub-nitride semiconductor layer may correspond to the odd-numbered layers 140C-1, 140C-3, ... from the first boundary I1 (Z=0), and the second sub-nitride semiconductor layer The semiconductor layer may correspond to layers 140C-2, 140C-4, ... located even-numbered from the first boundary I1 (Z=0). Alternatively, on the contrary, the second sub-nitride semiconductor layer may correspond to the odd-numbered layers 140C-1, 140C-3, ... from the first boundary I1 (Z=0), and the first sub The nitride semiconductor layer may correspond to layers 140C-2, 140C-4, ... located even-numbered from the first boundary I1 (Z=0).

Regardless of the arrangement of the first and second sub-nitride semiconductor layers, the content ratio of the first constituent (eg, In, Al) of the first sub-nitride semiconductor layer including the first constituent (eg, X, Y) ) May be smaller as it is disposed closer to the first nitride semiconductor layer 130 and may be larger as it is disposed closer to the anode 120. For example, when the first sub-nitride semiconductor layer is the layers 140C-1, 140C-3, ..., 140C-(N-2), 140C-N, the first sub-nitride semiconductor layer 1 The content ratio (eg: X, Y) of constituents (eg: In, Al) is the largest in 140C-N, the smallest in 140C-1, and from the first boundary (I1) to the second boundary (I2). It can increase as you go. Accordingly, the average value of the content ratio of the first constituent components of the first and second sub-nitride semiconductor layers may increase from the first nitride semiconductor layer 130 to the anode 120. That is, the average value may converge to the increasing changes 152, 154, and 156 shown in FIGS. 6A to 6C. In this case, the thicknesses of the first and second sub-nitride semiconductor layers may be uniform.

FIG. 8 is a diagram illustrating a change in thickness of the first and second sub-nitride semiconductor layers in the second nitride semiconductor layer 140C.

Alternatively, the thickness of the plurality of first sub-nitride semiconductor layers may be thinner as they are disposed closer to the first nitride semiconductor layer 130 and thicker as they are disposed closer to the anode 120. In this case, the thickness of the second sub-nitride semiconductor layer disposed between the first sub-nitride semiconductor layers may be constant.

Referring to FIG. 8, the first sub-nitride semiconductor layer including the first component may include the 1-1 to 1-5 sub-nitride semiconductor layers. A 1-1 sub-nitride semiconductor layer having a first thickness t1 is disposed at a position where Z is 0 to Z1, and a 1-2 sub-nitride semiconductor layer having a second thickness t2 is disposed at a position Z2 to Z3. And the 1-3 sub-nitride semiconductor layers of the third thickness t3 are disposed at positions Z4 to Z5, and the 1-4 sub-nitride semiconductor layers of the fourth thickness t4 are disposed at positions Z6 to Z7. In addition, sub-nitride semiconductor layers 1-5 having a fifth thickness t5 may be disposed at positions Z8 to Z9. In this case, the first to fifth thicknesses t1 to t5 are thick in the order of t5> t4> t3> t2> t1.

Also, the second sub-nitride semiconductor layer not including the first component may include the 2-1 to 2-4 sub-nitride semiconductor layers. The 2-1 sub-nitride semiconductor layer is disposed at the positions Z1 to Z2, the 2-2 sub-nitride semiconductor layer is disposed at the positions Z3 to Z4, and the 2-3 sub-nitride semiconductor layer is disposed at the positions Z5 to Z6. The semiconductor layer is disposed, and the 2-4 sub-nitride semiconductor layers are disposed at positions Z7 to Z8. The thicknesses of the 2-1 to 2-4 sub-nitride semiconductor layers may all be the same, but embodiments are not limited thereto.

When the first and second sub-nitride semiconductor layers have the thickness as illustrated in FIG. 8, the average value of the content ratios of the first constituents of all the first and second sub-nitride semiconductor layers is the first nitride semiconductor layer 130 ) To the anode 120 may increase. That is, the thicknesses of the first and second sub-nitride semiconductor layers may be determined so that the average value converges to the increase changes 152, 154, and 156 shown in FIGS. 6A to 6C.

In this case, as shown in FIG. 8, the content ratios (X, Y) of the first components included in the plurality of first sub-nitride semiconductor layers may have a constant value (k) and may be uniform.

9 is a diagram of another embodiment showing changes in thicknesses of first and second sub-nitride semiconductor layers in the second nitride semiconductor layer 140C.

Meanwhile, the thickness of the plurality of first sub-nitride semiconductor layers is constant, and the thickness of the second sub-nitride semiconductor layer disposed between the first sub-nitride semiconductor layers is the first nitride semiconductor layer 130 (that is, the first boundary ( The closer to I1)), the thicker it may be, and the closer to the anode 120 (that is, the second boundary I2), the thinner may be.

Referring to FIG. 9, the second sub-nitride semiconductor layer not including the first component (ie, X or Y is 0) may include the 2-1 to 2-6 sub-nitride semiconductor layers. A 2-1 sub-nitride semiconductor layer having a first thickness t1' is disposed at a position where Z is 0 to Z1', and a 2-2 sub-second thickness t2' at a position Z2' to Z3' A nitride semiconductor layer is disposed, a 2-3 sub-nitride semiconductor layer is disposed at a position Z4' to Z5' and a third thickness t3', and a fourth thickness t4' at a position Z6' to Z7' The 2-4th sub-nitride semiconductor layer of is disposed, and the 2-5th sub-nitride semiconductor layer of the fifth thickness (t5') is disposed at positions Z8' to Z9', A 2-6th sub-nitride semiconductor layer having a thickness of 6 ′ may be disposed. In this case, the first to sixth thicknesses t1' to t6' may be thicker in the order of t6'> t5'> t4'> t3'> t2'> t1'.

In addition, the first sub-nitride semiconductor layer including the first component (ie, X or Y is not 0) may include the 1-1 to 1-6 sub-nitride semiconductor layers. The 1-1 sub-nitride semiconductor layer is disposed at the position where Z is Z1' to Z2', the 1-2 sub-nitride semiconductor layer is disposed at the position Z3' to Z4', and the position Z5' to Z6' is The 1-3 sub-nitride semiconductor layers are arranged, the 1-4 sub-nitride semiconductor layers are arranged at positions Z7' to Z8', and the 1-5 sub-nitride semiconductor layers are arranged at positions Z9' to Z10' And the 1-6th sub-nitride semiconductor layers are disposed at positions Z11' to Z12'. The thicknesses of the 1-1 to 1-6 sub-nitride semiconductor layers may all be the same, but embodiments are not limited thereto.

When the first and second sub-nitride semiconductor layers have the thickness as illustrated in FIG. 9, the average value of the content ratio of the first component of all the first and second sub-nitride semiconductor layers is the first nitride semiconductor layer 130 ) To the anode 120 may increase. That is, the thicknesses of the first and second sub-nitride semiconductor layers may be determined so that the average value converges to the increase changes 152, 154, and 156 shown in FIGS. 6A to 6C.

In this case, as shown in FIG. 9, the content ratios (X, Y) of the first constituent components included in the plurality of first sub-nitride semiconductor layers may have a constant value (k') and may be uniform.

Hereinafter, a second nitride semiconductor layer is disposed between the first nitride semiconductor layer 130 and the anode 120, and the content ratio of the first component of the second nitride semiconductor layer 140 is determined from the first boundary I1. 2 The accompanying diagram for the power semiconductor device 100 according to the above-described embodiment increasing toward the boundary I2 has superior characteristics than the conventional power semiconductor devices 10A and 10B shown in FIGS. 1A and 2A It will be described as follows with reference to.

10A and 10B show energy band diagrams when the conventional power semiconductor device 10A shown in FIG. 1A is reverse biased and forward biased, respectively. Here, Ec represents the energy level of the conduction band. Here, q represents the amount of charge and φ _b represents the Schottky barrier.

Referring to FIG. 10A, in the conventional power semiconductor device 10A, a strong electric field 164 is generated at the boundary between the n-GaN layer 9 and the Schottky electrode 11 under reverse bias conditions. The n-GaN layer 9 may have many screw dislocations 162, and electrons enter the potential 162 from the Schottky electrode 11 as indicated by the arrow 166, A large leakage current may be caused as indicated by the arrow 22 in 1b.

Referring to FIG. 10B, in the conventional power semiconductor device 10A, under a forward bias condition, the flow of the electrons 168 in the arrow direction 170 is limited only by the Schottky barrier φ _b , and thus, as shown in FIG. 1B. As shown, the forward bias turn-on voltage is not relatively large when compared to FIG. 2B. Here, qφ _b may be, for example, 1.0 eV.

11A and 11B show energy band diagrams when the conventional power semiconductor device 10B shown in FIG. 2A is reverse biased and forward biased, respectively. Here, Ec, q, and φ _b are as described above in FIGS. 10A and 10B.

Referring to FIG. 11A, in the conventional power semiconductor device 10B, under a reverse bias condition, the electric field 172 at the boundary between the InGaN layer 13 and the Schottky electrode 11 is substantially reduced, compared with FIG. 10A. When it is relatively small. Thus, the current flowing through the screw defect 174 depending on the electric field at the boundary between the InGaN layer 13 and the Schottky electrode 11 is substantially reduced as compared to Fig. 10A.

However, referring to FIG. 11B, in the conventional power semiconductor device 10B, under a forward bias condition, a conduction band energy barrier 176 is added to the Schottky barrier φ _b , so that the InGaN layer 13 and n-GaN At the boundary 178 between the layers 9 the energy barrier of the conduction band becomes very large. For this reason, since electrons 180 must cross a high energy barrier in order to move to the Schottky electrode 11, there is a problem in that the forward bias turn-on voltage increases as indicated by arrows 26 in FIG. 2B. Here, qφ _b is, for example, 0.8 eV, the added energy barrier 176 is 0.62 eV, and the total energy barrier that the electron 180 must cross may be 1.42 eV.

12A and 12B show energy band diagrams when the power semiconductor device 100 of the embodiment shown in FIG. 3 is reverse biased and forward biased, respectively. Here, Ec, q, and φ _b are as described above in FIGS. 10A and 10B.

In the power semiconductor device 100 of the embodiment, the second nitride semiconductor layer 140 having a first component whose content ratio increases from the first boundary I1 to the second boundary I2 is formed of the anode 120 and the first boundary. It is disposed between the nitride semiconductor layers 130. Accordingly, referring to FIG. 12A, under the reverse bias condition, the electric field 182 at the boundary between the second nitride semiconductor layer 140 and the anode 120 is substantially reduced, and is relatively small compared to FIG. 10A. Thus, the leakage current dependent on this electric field 182 and flowing through the screw defect 184 is relatively small compared to Fig. 1A (or Fig. 10A).

Further, referring to FIG. 12B, in the power semiconductor device 100 of the embodiment, under the forward bias condition, the conduction band energy barrier 186 added to the Schottky barrier φ _b is the energy barrier 176 shown in FIG. 11B. Is relatively smaller than Therefore, compared with FIG. 11B, the electrons 188 are relatively easy to move toward the anode 120 so that the forward bias turn-on voltage Vf3 is lower than the forward bias turn-on voltage Vf2 in FIG. 2B. Here, qφ _b is, for example, 0.8 eV, and the added energy barrier 186 is 0.38 eV, and the total energy barrier that the electron 188 must cross is 1.18 eV, which is greater than the case of FIG. 10B, but than the case of FIG. 11B. It can be seen that it is small.

Meanwhile, the reason why the energy barrier 186 added in FIG. 12B is smaller than the energy barrier 176 shown in FIG. 11B is as follows.

As a first reason, since the content ratio of In in the InGaN layer 13 shown in FIG. 2A is fixed, all polarization charges are located at the boundary between the InGaN layer 13 and the n-GaN layer 9, and the electric field is at this boundary. It changes discontinuously at the point. Further, the electric field in the InGaN layer 13 is not changed and is constant. On the other hand, as in the present embodiment, the content ratio (eg, X, Y) of the first component (eg, In, Al) included in the second nitride semiconductor layer 140 is determined from the first boundary I1. Since it increases to the second boundary I2, the polarization charge is uniformly located over the entire second nitride semiconductor layer 140, and the electric field in the second nitride semiconductor layer 140 may continuously change.

As a second reason, the energy discontinuity in the conduction band is unfolded due to the interposition of the second nitride semiconductor layer 140 in the case of the embodiment.

Hereinafter, when the first nitride semiconductor layer 130 is implemented with GaN and the second nitride semiconductor layer 140 is implemented with In _X Ga _(1-X) N, the existing power semiconductor devices 10A and 10B The current-voltage characteristics of the power semiconductor device 100 of the embodiment are compared and looked at as follows.

13 is a graph showing a comparison between the conventional power semiconductor devices 10A and 10B and the forward bias current-voltage characteristics 202, 206, and 204 of the power semiconductor device 100 according to the present embodiment, respectively.

The horizontal axis of FIG. 13 represents the voltage applied to the semiconductor devices 10A, 10B, 100, that is, the forward bias voltage V _ac applied between the anode 120 and the cathode 110, and the vertical axis represents the current density. ). Here, reference numeral '202' denotes a current-voltage characteristic of the power semiconductor element 10A shown in FIG. 1A, and reference numeral '206' denotes a current-voltage characteristic of the power semiconductor element 10B illustrated in FIG. 2A. And reference numeral '204' denotes a current-voltage characteristic of the power semiconductor device 100 shown in FIG. 3.

Referring to FIG. 13, the forward bias turn-on voltage Vf3 of the power semiconductor device 100 according to the embodiment is greater than the forward bias turn-on voltage Vf1 of the conventional power semiconductor device 10A. It can be seen that it is less than the forward bias turn-on voltage Vf2 of the power semiconductor device 10B.

14A to 14C are graphs showing energy bands compared in a situation in which the power semiconductor devices 10A, 10B, and 100 are reverse biased, where Ec represents the energy level of the conduction band, and Ev represents the valence band. Represents the energy level of, and m represents the distance from the Schottky electrode 11 (or the anode 120) to the ohmic electrode 5 (or the cathode 110). That is, m=0 at the point where the Schottky electrode 11 (or the anode 120) is disposed.

It can be seen that when a reverse bias voltage of -300 volts is applied to the ohmic electrode 5 and the Schottky electrode 11 shown in FIG. 1A, the electric field is formed very large around m=0 as shown in FIG. 14A. have. In this case, the electric field E (m=0) may be expressed as in Equation 1 below.

Here, V represents the voltage applied to the power semiconductor device 10A, N _D represents the density of donor ions contained in the n-GaN layer 9, and ε _r represents the n- GaN layer 9 Represents the relative permittivity of and ε ₀ represents the permittivity in free space.

When a reverse bias voltage of -300 volts is applied to the ohmic electrode 5 and the Schottky electrode 11 shown in FIG. 2A, the electric field near m=0 as shown in FIG. 14B is compared with FIG. 14A. It can be seen that it is relatively low. In this case, the electric field may be expressed as in Equation 2 below.

Here, V represents the voltage applied to the power semiconductor device 10B, and P _S represents the surface polarization charge at the boundary between the InGaN layer 13 and the n-GaN layer 9 shown in FIG. 2A.

When a reverse bias voltage of -300 volts is applied to the anode 120 and cathode 110 shown in FIG. 3, it can be seen that the electric field near m=0 is low as shown in FIG. 14C. In this case, the electric field may be expressed as in Equation 3 below.

Here, V represents the voltage applied to the power semiconductor device 100, P represents the volume polarization charge in the In _X Ga _(1-X) N layer 140, and m ₁ represents In _X Ga _{(1-X ) It} represents the thickness of the N layer 140.

15 is a graph showing a comparison of the conventional power semiconductor devices 10A and 10B and reverse bias current-voltage characteristics 212 and 214 of the power semiconductor device 100 according to the present embodiment, respectively, and the horizontal axis is a power semiconductor device It represents the reverse bias voltage (V _ac ) applied between the anode and the cathode of (10A, 10B, 100), and the vertical axis represents the current density. Here, reference numeral '212' denotes a current-voltage characteristic of the power semiconductor element 10A shown in FIG. 1A, and reference numeral '214' denotes the power semiconductor element 10B and 100 shown in FIGS. 2A and 3. It shows the current-voltage characteristics.

Referring to FIG. 15, the reverse bias leakage current 214 of the power semiconductor device 100 according to the embodiment is smaller than the leakage current 212 of the conventional power semiconductor device 10A, and the other power semiconductor device 10B It can be seen that it is the same as the leakage current of ).

In addition, the power semiconductor device described above is a multi-function sensor such as a photodetector, a gas sensor, a liquid sensor, a pressure sensor, and pressure and temperature in various fields, for example. sensor), a power switching transistor, a microwave transistor, and a power converter.

Hereinafter, the configuration and operation of the power converter including the power semiconductor device according to the above-described embodiment will be described with reference to the accompanying drawings.

16 is a circuit diagram of a power semiconductor device according to an embodiment. Here, Vdc represents the DC supply voltage.

The power semiconductor device shown in FIG. 16 includes a freewheel diode 300 and an IGBT (Isulated Gate Bipolar Transistors) 400 and an inductor L as a passive device.

The free wheel diode 300 shown in FIG. 16 is functionally separated to operate as a pn diode D or SBD, and has a gate to select the separated function. This diode 300 is also referred to as a gate controlled diode. Here, the SBD may correspond to the power semiconductor device shown in FIG. 3 described above.

The gate control diode 300 operates as a pn diode (D) in a conduction state and operates as if it is an SBD in a reverse state, thereby making full use of the two types.

The gate of the IGBT 400 connected in series with the gate control diode 300 remains turned off until just before the IGBT 400 is turned on, and the gate of the gate control diode 300 is from the pn diode D. In order to switch to SBD, it is turned on to be in a conduction state to prepare the reverse state.

When the gate of the IGBT 400 is turned on, since the Schottky diode is already in a conductive state, the accumulated charge amount is much less than that of the pn diode D. Therefore, the reverse current can be reduced. Also, just before the IGBT 400 is turned off, the gate of the gate control diode 300 switches from SBD to the pn diode D to reduce the forward voltage in the conduction state. After being turned on and just before the IGBT 400 is turned on again, the pn diode D enters a conductive state, and the conduction state is switched from the pn diode D to the SBD. The above-described operation is repeatedly performed.

In order to drive the gate control diode 300 and the IGBT 400, a gate driving circuit (not shown) may be further disposed. The gate driving circuit generates a gate control signal V _GA to be supplied to the gate control diode 300 and switches the gate from the pn diode D to the SBD. In addition, the gate driving circuit generates a gate control signal V _GE and outputs it to the IGBT 400.

That is, when current flows through the gate control diode 300 in the forward direction, at least the pn diode D operates, and when the gate control diode 300 recovers in the reverse direction, the SBD mainly operates. 300, 400).

The embodiments have been described above, but these are only examples and do not limit the present invention, and those of ordinary skill in the field to which the present invention belongs are not illustrated above within the scope not departing from the essential characteristics of the present embodiment. It will be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be modified and implemented. And differences related to these modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

100: power semiconductor element 110: cathode
120: anode 130: first nitride semiconductor layer
132: 1-1 nitride semiconductor layer 134, 134A, 134B: 1-2 nitride semiconductor layer
140, 140A, 140B, 140C: second nitride semiconductor layer

Claims (22)

cathode;
A first nitride semiconductor layer disposed on the cathode;
An anode disposed on the first nitride semiconductor layer; And
And a second nitride semiconductor layer disposed between the first nitride semiconductor layer and the anode in contact with the first nitride semiconductor layer and the anode, respectively,
The second nitride semiconductor layer,
A plurality of first sub-nitride semiconductor layers containing a first constituent made of indium (In) or aluminum (Al) and a plurality of second sub-nitride semiconductor layers not containing the first constituent are alternately arranged and repeated Become,
The thickness of the plurality of first sub-nitride semiconductor layers is thinner when disposed closer to the first nitride semiconductor layer and thicker when disposed closer to an anode, and the thickness of the plurality of second sub-nitride semiconductor layers is constant. The method of claim 1, wherein the first nitride semiconductor layer and the second nitride semiconductor layer have different components, the first nitride semiconductor layer contains GaN, and the second nitride semiconductor layer contains In. Contains as a constituent and GaN as a second constituent, or
Constituent components of the first nitride semiconductor layer and the second nitride semiconductor layer are the same, the first nitride semiconductor layer contains AlGaN, the second nitride semiconductor layer contains Al as the first component, A power semiconductor device containing GaN as a second component. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete The power semiconductor element according to any one of claims 1 and 2; And
A power semiconductor circuit comprising a passive device electrically connected to the power semiconductor device.

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