Stacked III-V semiconductor diode

Abstract

A stacked III-V semiconductor diode, comprising GaAs or consisting of GaAs, having a highly n-doped cathode layer, a highly p-doped anode layer, and a drift region disposed between the cathode layer and the anode layer, the drift region having a dopant concentration of at most 8·10<supgt;15< / supgt> cm<supgt;‑3< / supgt> and a layer thickness of at least 10 μm, wherein the cathode layer has a δ-layer section having a layer thickness ranging from 0.1 μm to 2 μm and a dopant concentration of at least 1·10<supgt;19< / supgt> cm<supgt;‑3< / supgt>.

Description

Field of Technology

[0001] The present invention relates to a stacked III-V semiconductor diode, which comprises GaAs or consists of GaAs, and has a highly n-doped cathode layer, a highly p-doped anode layer, and a drift region arranged between the cathode layer and the anode layer. Background Art

[0002] The p-n-n structure of a high-voltage semiconductor diode made of gallium arsenide is known from "GaAs Power Devices" by Ashkinazi of Germany, ISBN 965-7094-19-4, pages 8 and 9. + -n-n + Structured high-voltage semiconductor diode.

[0003] Other stacked III-V semiconductor diodes are known from EP 3 321 971 B1 and from EP 3 321 970 B1, wherein the semiconductor diode has an additional intermediate layer between the drift region and the cathode or the anode. Summary of the Invention

[0004] In this context, the object of the present invention is to describe a device that extends the prior art.

[0005] This object is solved by a stacked III-V semiconductor diode according to the present invention. Advantageous configurations of the present invention are preferred embodiments.

[0006] According to the subject matter of the present invention, there is provided a stacked III-V semiconductor diode comprising GaAs or consisting of GaAs, which has a highly n-doped cathode layer and a highly p-doped anode layer.

[0007] A drift region is arranged between the cathode layer and the anode layer, and the drift region has a dopant concentration of at most 8·10 15 cm -3 and a layer thickness of at least 10 μm. Preferably, the total layer thickness of the drift region is at most 50 μm or at most 100 μm.

[0008] The cathode layer has a first section and a second section.

[0009] The first section is configured as a δ-layer section having a layer thickness between 0.1 μm and 1 μm or between 0.1 μm and 2 μm.

[0010] The δ-layer section has a dopant concentration of at least 1·10 19 cm -3 or at least 2·10 19 cm -3 of the dopant concentration.

[0011] It is understood that all semiconductor layers of a semiconductor diode composed of or including GaAs - namely, in particular, the cathode layer, the anode layer, and the drift region - are each composed of GaAs or at least include GaAs. In other words, each semiconductor layer of a group III - V semiconductor diode has at least the elements Ga and As.

[0012] Furthermore, it is understood that a pn - junction is constructed within the drift region.

[0013] It should be noted that the semiconductor layers of the semiconductor diode are constructed stacked one above the other. Preferably, the semiconductor layers have equal areas. Preferably, one of the semiconductor layers is constructed as a substrate layer or includes a substrate layer. In an extended embodiment, the substrate layer has a larger area compared to the stack of semiconductor layers arranged on the substrate layer.

[0014] Preferably, the substrate layer has a thickness between 50 μm and 120 μm or between 50 μm and 250 μm. In an extended embodiment, in the case of p - doping, the substrate layer has a concentration in the range between 1·10 17 cm -3 and 2·10 18 cm -3 or between 1·10 17 cm -3 and 8·10 18 cm -3 respectively.

[0015] The semiconductor layers are preferably produced epitaxially one above the other. Particularly preferably, the cathode layer or the anode layer is constructed from the substrate layer on which all other semiconductor layers grow epitaxially in succession. Alternatively, the layers are connected by wafer bonding.

[0016] Furthermore, it is understood that the semiconductor diode preferably has other layers made of other materials, in particular metal contact layers.

[0017] Furthermore, it should be noted that the term anode and the term anode layer, as well as the term cathode and the term cathode layer, are used synonymously, respectively.

[0018] The contact layer is composed, for example, entirely or partially of a metal (such as gold) or of a metal alloy and is produced, for example, by electron beam evaporation or by sputtering.

[0019] The regions of the cathode layer and the anode layer adjacent to the connection layer preferably have a higher dopant concentration compared to the corresponding other parts of the cathode layer and the anode layer, in order to construct an electrically conductive connection with as low a resistance as possible and to keep the series resistance or power loss of the semiconductor diode as low as possible.

[0020] Very high doping can be achieved in GaAs layers or GaAs-based layers, at least at relatively low thicknesses, i.e., preferably less than 1 μm, especially with a doping of at least 1·10 19 cm -3 and good layer quality. Suitable dopants for the cathode layer in particular are, for example, tellurium or selenium.

[0021] Accordingly, the layer thickness of the second section of the cathode layer essentially depends on the lifetime or penetration depth (Eindringtiefe) of the minority carriers, i.e., holes. Usually, a few hundred nanometers to a maximum of 2 μm is sufficient as the layer thickness of the second layer.

[0022] In other words, the thickness of the second section of the cathode layer is preferably as thick as the mean free path (freie ) of the minority carriers (i.e., holes in the cathode).

[0023] Furthermore, the δ-layer section forms a quasi-barrier for the minority carriers and reduces the contact resistance. The turn-off characteristics of the diode are particularly improved by the δ-layer section and thus the switching characteristics are improved.

[0024] Studies have shown that the combination of a thin but very highly doped δ-layer section of the cathode layer and a less doped second section can improve the emitter efficiency, i.e., the efficiency of the cathode.

[0025] Combined with a low-doped drift region, a diode can be manufactured that has a particularly high blocking voltage of more than 1100 V or even more than 1200 V, a small on-resistance, and a particularly low capacitance per unit area.

[0026] In one embodiment, the cathode layer has a second layer section that has a lower dopant concentration than the dopant concentration of the δ-layer section, such that the δ-layer section supplements the typical cathode layer to some extent with a δ-doping peak.

[0027] Preferably, the δ-layer section has a material-locked (stoffschlüssig) connection to the second metal connection. In other words, the metal connection is arranged on the upper side of the cathode layer.

[0028] On the lower side of the anode layer is a first metal connection. Preferably, two metal connections cover the anode layer and / or the cathode layer in the central region or almost completely or completely, in order to achieve a low connection resistance. It is understood that even in the case of complete coverage, the peripheral edge sections are not the most metallized, in order to improve process reliability.

[0029] In an extended embodiment, the second layer section of the cathode layer has a lower dopant concentration compared to the δ layer section. Preferably, the second layer section of the cathode layer has a greater layer thickness D compared to the δ layer section K2 。

[0030] Preferably, the second layer section of the cathode layer has a thickness ranging from at least 0.5 μm to a maximum of 1.5 μm or from at least 0.5 μm to a maximum of 2.5 μm or from at least 0.5 μm to a maximum of 5 μm.

[0031] It should be noted that the terms doping and dopant concentration are used synonymously. Furthermore, it should be noted that the change in doping between the δ layer section and the second section of the cathode layer preferably occurs stepwise. In other words, the doping preferably changes within a thickness range of less than 0.1 μm or less than 0.05 μm.

[0032] The dopant concentration of the second layer section of the cathode layer is lower than 1·10 19 cm -3 。Preferably, the dopant concentration of the second layer section of the cathode layer is higher than 1·10 18 cm -3 or higher than 2·10 18 cm -3 or higher than 5·10 18 cm -3 。

[0033] In an extended embodiment, the cathode layer has a transition layer section wherein the transition layer section is arranged between the second section of the cathode layer and the drift region, and has a layer thickness of at least 3 μm, a doping lower than that of the second section, a doping higher than that of the drift region, and a doping concentration change process that is convex or concave or linear or stepped descending in the direction of the drift region.

[0034] In another embodiment, the δ layer section has Te and / or Se as dopants. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be explained in more detail below with reference to the drawings. Herein, like components are labeled with the same names. The illustrated embodiments are highly schematic, i.e., the spacings as well as the lateral and vertical extensions are not to scale and do not have any derivable geometric relationships with each other unless otherwise stated. Shown herein are:

[0036] Figure 1 View showing a first embodiment of a stacked III-V semiconductor diode

[0037] Figure 2 View showing a first embodiment of the dopant concentration variation process of a III-V semiconductor diode

[0038] Figure 3 View showing another embodiment of a stacked III-V semiconductor diode

[0039] Figure 4 View showing another embodiment of a stacked III-V semiconductor diode

[0040] Figure 5 View showing another embodiment of a stacked III-V semiconductor diode

[0041] Figure 6 View showing another embodiment of the dopant concentration variation process Detailed implementation

[0042] Figure 1 The image of shows a view of a first embodiment of a stacked III-V semiconductor diode 10, which is made of or consists of GaAs. It has a total thickness D A The highly doped p-doped substrate layer with thickness D forms the anode layer 12, on which a drift region 14 with total thickness D is arranged D , followed by a highly n-doped cathode layer 16 with layer thickness D K .

[0043] It can be understood that a pn junction is formed in the drift region 14

[0044] The cathode layer 16 has a first section 16.1 and a second section 16.2

[0045] The first section 16.1 of the cathode layer 16 is formed as a δ-layer section, which has a very high dopant concentration of at least 1·10 19 cm -3 or at least 2·10 19 cm -3 and a low layer thickness D ranging from 0.1 μm to 1 μm or from 0.1 μm to a maximum of 2 μm K1 .

[0046] Compared with the δ-layer section 16.1, the second section 16.2 has a lower dopant concentration and a larger layer thickness D K2 .

[0047] The layer thickness of the second layer section 16.2 of the cathode layer 16 has a thickness in the range between 0.5 μm and 1.5 μm or in the range between 0.5 μm and 2.5 μm or in the range between 0.5 μm and 5 μm.

[0048] The dopant concentration of the second layer section 16.2 is lower than 1·10 19 cm -3 . Preferably, the dopant concentration of the second layer section 16.2 is higher than 1·10 18 cm -3 or higher than 2·10 18 cm -3 or higher than 5·10 18 cm -3 .

[0049] A metal connection M1 is arranged on the lower side of the anode layer 12, and a metal connection M2 is arranged on the upper side of the cathode layer 16.

[0050] Preferably, the two metal connections M1, M2 almost completely cover the anode layer 12 and / or the cathode layer 16 in order to achieve a low connection resistance. The δ layer section 16.1 also has a material-locked connection to the material of the metal connection M2.

[0051] In Figure 2 the image shows the dopant concentration profile along the thickness of the stacked III-V semiconductor diode 10 shown in Figure 1 .

[0052] The dopant concentration D is plotted on the position x along the stack of the III-V semiconductor diode 10.

[0053] The dopant concentration profile is constructed to be constant on the respective layer thicknesses D K2 and D K1 of the two sections 16.2 and 16.1 of the cathode layer 16, thereby creating a dopant concentration jump between the second layer section 16.2 and the δ layer section.

[0054] Then the dopant concentration drops abruptly to a very low level in the region of the drift region 14, which is at most 8·10 15 cm -3 . At the transition from the drift region 14 to the anode layer, the dopant concentration jumps abruptly to a uniformly high level of the p-dopant concentration.

[0055] The dopant concentration along the anode 12 is constant, where the magnitude of the dopant concentration is less than the dopant concentration of the second region 16.2 of the cathode 16.

[0056] In the illustrated embodiment, the drift region has a low and substantially constant dopant concentration. Here, the doping changes between n-dopant and p-dopant along the entire layer thickness, thereby creating a pn junction in the drift region 14.

[0057] In Figure 3 the embodiment shown, the metal connection accesses M1 and M2 are configured in a planar manner.

[0058] In addition to the first section 16.1 and the second section 16.2, the cathode layer 16 also has a transition layer section 16.3. The transition layer section 16.3 has a layer thickness D of at least 3 μm and, for example, at most 10 μm or at most 5 μm. K3 .

[0059] The transition layer section 16.3 of the cathode layer 16 has a lower doping than the second section 16.2 of the cathode layer 16 and a higher doping than the drift region 14.

[0060] The dopant concentration profile decreasing in the direction of the drift region 14 within the transition layer section 16.3 is configured convexly or concavely or linearly or stepwise.

[0061] In Figure 4 the embodiment, the two metal access layers M1, M2 each cover only the central part of the anode or the cathode. The transition layer section 16.3 is not configured, so that the second section 16.2 of the cathode directly adjoins the drift region 14.

[0062] In Figure 5 the embodiment shown, in addition to the second layer section 16.2, the cathode layer 16 also has a transition layer section 16.3.

[0063] A p-doped transition layer section 12.3 is configured between the drift region 14 and the second section 12.2 of the anode layer 12 as part of the anode layer 12.

[0064] The dopant concentration of the transition layer section 12.3 of the anode increases in the direction of the second section 12.2 of the anode layer 12 along the layer thickness of the transition layer section 12.3. The increase in doping is configured concavely or convexly or linearly or stepwise.

[0065] In Figure 6 the image shows the dopant concentration profile for the embodiment in combination with Figure 5 the embodiment shown. Only the differences from Figure 2 the embodiment are explained below.

[0066] The δ-layer section 16.1 of the cathode layer 16 is arranged on the side of the second section 16.2 facing away from the drift region 14, so that the dopant concentration drops stepwise in the direction of the drift region 14 along the cathode layer.

[0067] Between the second section 16.2 of the cathode layer 16 and the drift region 14, a transition layer section 16.3 is further constructed as part of the cathode layer 16.

[0068] The dopant concentration of the transition layer section 16.3 of the cathode layer 16 decreases during a further course in the direction of the drift region 14.

[0069] Between the drift region 14 and the second section 12.2 of the anode layer 12, a p-doped transition layer section 12.3 is constructed as part of the anode layer 12. The dopant concentration of the transition layer section 12.3 of the anode layer 12 increases during a further course in the direction of the second section 12.2 of the anode layer 12.

Claims

1. A stacked III-V semiconductor diode (10), the stacked III-V semiconductor diode comprising GaAs or consisting of GaAs, the stacked III-V semiconductor diode having a highly n-doped cathode layer (16), a highly p-doped anode layer (12), and A drift region (14), the drift region being arranged between the cathode layer (16) and the anode layer (12), and the drift region having a dopant concentration of at most 8·10 15 cm -3 , and a layer thickness (D D ) of at least 10 μm and at most 80 μm, or a layer thickness (D D ) of at least 10 μm and at most 100 μm, characterized in that The cathode layer (16) has a first section (16.1) and a second section (16.2), and the first section is configured as a δ-layer section having a layer thickness (D K1 ) between 0.1 μm and 1 μm or between 0.1 μm and 2 μm, and the first section has a dopant concentration of at least 1·10 19 cm -3 or at least 2·10 19 cm -3 , wherein the second section (16.2) is arranged between the first section (16.1) and the drift region (14). Compared with the δ-layer section, the second section (16.2) of the cathode layer (16) has a lower dopant concentration, and the second section (16.2) of the cathode layer (16) has a dopant concentration higher than 1·10 18 cm -3 .

2. The stacked III-V semiconductor diode (10) according to claim 1, characterized in that, the δ-layer section (16.1) is adjacent to the metal cathode contact layer (M1) with material locking.

3. The stacked III-V semiconductor diode (10) according to claim 1 or 2, characterized in that, The change in doping between the δ-layer section and the second section (16.2) of the cathode layer (16) occurs in a stepwise manner.

4. The stacked III-V semiconductor diode (10) according to any one of the preceding claims, characterized in that, The second section (16.2) of the cathode layer (16) has a dopant concentration of less than 1·10 19 cm -3 and higher than 2·10 18 cm -3 or has a dopant concentration of less than 1·10 19 cm -3 and higher than 5·10 18 cm -3 of the dopant concentration.

5. The stacked III-V semiconductor diode (10) according to any one of the preceding claims, characterized in that, The second section (16.2) of the cathode layer (16) has a layer thickness (D K2 ) between 0.5 μm and 1.5 μm, or between 0.5 μm and 2.5 μm, or between 0.5 μm and 5 μm.

6. The stacked III-V semiconductor diode (10) according to any one of the preceding claims, characterized in that, The cathode layer (16) has a transition layer section (16.3), wherein the transition layer section (16.3) is arranged between the second section (16.2) and the drift region (14) and has a layer thickness (D K3 ) of at least 3 μm, and the transition layer section (16.3) has a lower dopant concentration than the second section (16.2), and the transition layer section (16.3) has a higher dopant concentration than the drift region (14), and the dopant concentration profile has a dopant concentration profile that decreases convexly or concavely or linearly or stepwise in the direction of the drift region (14).

7. The stacked III-V semiconductor diode (10) according to any one of the preceding claims, characterized in that, The anode layer (12) has a first section (12.1) and a second section (12.2), the second section being arranged between the first section (12.1) and the drift region (14), and the dopant concentration of the second section (12.2) being less than the dopant concentration of the first section (12.1), or the dopant concentration of the second section (12.2) being equal to the dopant concentration of the first section (12.1).

8. The stacked III-V semiconductor diode (10) according to any one of the preceding claims, characterized in that, The dopant concentration of the first section (12.1) of the anode layer (12) is at least 8·10 17 cm -3 and at most 4·10 18 cm -3 or at least 8·10 17 cm -3 and at most 8·10 18 cm -3 and the dopant concentration of the second section of the anode layer (12) is at least 1·10 17 cm -3 and at most 8·10 17 cm -3 .

9. The stacked III-V semiconductor diode (10) according to any one of the preceding claims, characterized in that, The anode layer (12) has a transition section (12.3) adjacent to the drift region (14), wherein the transition section (12.3) has a dopant concentration change that is convex or concave or linear or stepped downward in the direction of the drift region (14) and has a dopant concentration: the dopant concentration is greater than the dopant concentration of the p-doped drift region and less than the dopant concentration of the second section (12.2) of the anode layer (12).

10. The stacked group-III-V semiconductor diode (10) according to any one of the preceding claims, characterized in that, The second section (12.2) of the anode layer (12) has a smaller doping compared to the second section (16.2) of the cathode layer (16).

11. The stacked III-V semiconductor diode (10) according to any one of the preceding claims, characterized in that, The δ-layer section (16.1) has Te or Se as a dopant.

12. The stacked III-V semiconductor diode (10) according to claim 3, characterized in that, The doping between the δ-layer section and the second section (16.2) of the cathode layer (16) changes within a thickness range of less than 0.1 μm.

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