Stacked iii-v semiconductor diode
Patent Information
- Application Number
- JP2024036282
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2021-02-08
- Filing Date
- 2024-03-08
- Publication Date
- 2025-06-03
- Estimated Expiration
- 2042-02-07
AI Technical Summary
Existing III-V semiconductor diodes face challenges in achieving high reverse voltage with low on-resistance and reverse recovery charge, particularly in GaAs-based devices, and there is a need for improved structural designs to enhance dielectric strength and switching speed.
A stacked III-V semiconductor diode design featuring a lightly n-doped and lightly p-doped drift region with specific layer thicknesses and dopant concentration ratios, along with a dopant concentration profile that gradually transitions to higher levels, is used to create a wide drift region with controlled p-n junctions and isoelectronic centers to enhance switching speed.
The design achieves diodes with reverse voltages exceeding 1100V and low on-resistance per area, while reducing power losses and improving switch-off behavior, with a reverse recovery charge as low as 80 nC per 100 nm.
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Abstract
Description
[Technical field]
[0001] The present invention relates to a stacked III-V semiconductor diode containing or consisting of GaAs, comprising a heavily n-doped cathode layer, a heavily p-doped anode layer, and a drift region disposed between the cathode and anode layers. [Background technology]
[0002] p + -nn + A high-voltage resistant semiconductor diode made of gallium arsenide having the structure is known from "GaAs Power Devices", ISBN 965-7094-19-4, pages 8 and 9, by German Ashkinazi.
[0003] Further stacked III-V semiconductor diodes are known from EP 3321971 and EP 3321970, in which the semiconductor diode has an additional intermediate layer between the drift region and the cathode or anode. Further semiconductor devices are known from EP 3321971, DE 102016111844 A1, JP 06-314801 A1 and DE 102018000395 A1. Summary of the Invention [Problem to be solved by the invention]
[0004] Against this background, the object of the present invention is to provide a device which is a further development of the prior art. [Means for solving the problem]
[0005] This problem is solved by a stacked III-V semiconductor diode having the features of claim 1. Advantageous configurations of the invention are the subject of the dependent claims.
[0006] In accordance with the subject matter of the present invention, a stacked III-V semiconductor diode is provided, which contains or consists of GaAs, has a heavily n-doped cathode layer, a heavily p-doped anode layer, and a drift region disposed between the cathode layer and the anode layer.
[0007] The drift region includes a lightly n-doped drift layer and a lightly p-doped drift layer, the n-doped drift layer being disposed between the p-doped drift layer and the cathode layer.
[0008] Both drift layers each have a thickness of at least 5 μm and a maximum of 8 × 10 15 cm -3 and a dopant concentration maximum value of
[0009] The mutual dopant concentration maxima of both drift layers have a ratio of 0.1 to 10.
[0010] The ratio of the thickness of the n-doped drift layer to the thickness of the p-doped drift layer is between 0.5 and 3.
[0011] Naturally, all the semiconductor layers of the semiconductor diode which consist of or contain GaAs, that is to say in particular the cathode layer, the anode layer and the drift region, respectively, consist of GaAs or at least contain GaAs.
[0012] In other words, each semiconductor layer of the III-V semiconductor diode comprises at least the elements Ga and As.
[0013] The semiconductor layer is preferably produced by epitaxy. In one refinement, the cathode layer or the anode layer may be constituted by a substrate layer on which another III-V semiconductor layer is preferably epitaxially grown, thereby constituting a III-V semiconductor diode.
[0014] Alternatively, the III-V semiconductor diode comprises at least one semiconductor bond, in which two GaAs semiconductor wafers or surfaces of a GaAs wafer are joined together.
[0015] Preferably, the doping of each GaAs semiconductor layer is provided during epitaxy, which is preferably performed by MOVPE and / or LPE.
[0016] In one refinement, the doping is carried out by ion implantation after the epitaxial growth additionally or alternatively instead of being provided during epitaxy.
[0017] However, the semiconductor diode preferably has a further layer made of a further material, in particular a metallic terminal contact layer, which for example consists completely or partly of a metal, for example gold or a metal alloy, and which is produced, for example, by electron beam evaporation or by sputtering.
[0018] At least the regions of the cathode and anode layers adjacent to the terminal contact layer preferably have a high dopant concentration, which allows for the formation of the lowest possible resistance contacts and keeps the series resistance or power losses of the semiconductor diode as low as possible.
[0019] The drift region is characterized by having a total width of at least 10 μm. Preferably, the total width is at least 20 μm, or at least 40 μm, or at least 60 μm. The total width is divided into a weakly p-doped region or layer and a weakly n-doped region or layer.
[0020] The layer thickness ratio of both drift layers is selected such that the n-doped drift layer is at least half as thick as the p-doped drift layer or the n-doped drift layer is at most three times as thick as the p-doped drift layer.
[0021] The dopant concentration of each of the two drift layers is as low as possible in the region adjacent to the respective other drift layer and possibly increases somewhat in a direction away from the other drift layer. In one refinement, the increased portion is formed by one or more steps.
[0022] Thus, a pn junction is formed in the drift region in an area having a very low dopant concentration.
[0023] The wide, lightly doped drift region of two different layers allows diodes with extremely high reverse voltages of more than 1100 V, or even more than 1200 V, to be realized and can be fabricated with low on-resistance and particularly low capacitance per area.
[0024] In one refinement, isoelectronic or equivalent electronic centers are incorporated in the p-doped drift and / or anode layers to improve the switching speed, i.e., forward and reverse switching. In this case, the isoelectronic or equivalent electronic centers are impurity complexes. The impurity cell complexes are energetically deep and significantly reduce the charge carrier lifetime, i.e., these isoelectronic or equivalent electronic centers scavenge charge carriers, especially in reverse operation.
[0025] In one embodiment the isoelectronic centres contain N and / or ZnO and / or Mn and / or main group III elements and / or main group V elements.
[0026] In another refinement, the concentration of isoelectronic centers is 5×10 11 cm -3 From 8×10 14 cm -3 range, or 5×10 12 cm -3 From 1×10 14 cm -3 range, or 1×10 13 cm -3 From 8×10 13 cm -3Preferably, the concentration of isoelectronic centres is lower by a factor of 1000 to 10, or a factor of 100 to 20, than the dopant concentration in the respective regions of the drift layer or anode layer.
[0027] In particular, the diode area is 1 mm 2 GaAs power diodes can be fabricated with a maximum reverse recovery charge of 80 nC per diode.
[0028] In one embodiment, the thickness of the n-doped drift layer is greater than the thickness of the p-doped drift layer. In another embodiment, the n-doped drift layer and / or the p-doped drift layer has a thickness of at least 20 μm or at least 40 μm. The very high thickness of both drift layers makes it possible in particular to improve the dielectric strength of the diode.
[0029] In one refinement, the n-doped drift layer has a dopant concentration profile along its thickness that increases in a direction towards the cathode layer to a dopant concentration maximum.
[0030] The gradual reduction in the dopant concentration of the n-doped drift layer in the direction towards the p-doped drift layer makes it possible in particular to achieve very low dopant concentrations and to form a controlled and reproducible pn junction.
[0031] In another alternative refinement, the p-doped drift layer has a dopant concentration profile that rises along the layer thickness in the direction towards the anode layer to a dopant concentration maximum value. As already mentioned, the rise can also be formed by a stepped or step-like profile.
[0032] The increasing dopant concentration profile can be configured in alternative embodiments to be linear, concave or convex. A convex increase can for example follow a Gaussian curve, a concave increase can for example follow an exponential function. Of course, the concentration profile can always be greater than 8×1015 cm -3 lower than the maximum doping of
[0033] In another refinement, the dopant concentration profile of the n-doped drift layer and / or the p-doped drift layer has one or more steps along the layer thickness, one or more or all of the steps having convex or concave or straight edges in alternative refinements.
[0034] In another embodiment, the dopant concentration profile of each of the drift layers is greater than 3×10 15 cm -3 A value less than or equal to 6×10 14 cm -3 A value less than or equal to 3×10 14 cm -3 A value less than or equal to 2×10 14 cm -3 It decreases by a value less than
[0035] In one refinement, the dopant concentration is greater than 5×10 along at least 80% of the thickness of the n-doped drift layer and / or the p-doped drift layer. 13 cm -3 Greater than.
[0036] In another embodiment, the cathode layer has a thickness of at least 1×10 18 cm -3 or at least 5×10 18 cm -3 or at least 8×10 18 cm -3 The dopant concentration is
[0037] In yet another embodiment, the anode layer comprises at least 1×10 17 cm -3 or at least 5×10 17 cm -3 or at least 8×10 18 cm -3The light doping makes it possible to improve the switch-off behavior of the diode and to reduce the reverse recovery charge.
[0038] It should be noted that in order to keep the series resistance of the diode as low as possible or to form the lowest possible resistance contacts, a dopant concentration as high as possible is desired, especially in the regions of the cathode and anode layers adjacent to the metallic terminal contacts.
[0039] In another refinement, the cathode and / or anode layer has a thickness of at least 2 μm, or at least 5 μm, or at least 20 μm. A small thickness makes it easier to keep the series resistance of the diode low.
[0040] In yet another refinement, the cathode layer and / or the anode layer has a first section with a constant dopant concentration profile and a second section arranged between the first section and the drift region with a linear and / or concave and / or stepped dopant concentration profile in a direction towards the first section. Preferably, the stepped dopant concentration region has one or two or three steps or consists of one or two or three steps.
[0041] The second layer section makes it possible in particular to create a transition in the dopant concentration from a low level in the area of the drift region to a significantly higher level in the second section of the anode layer and / or cathode layer.
[0042] In an embodiment, the second layer section has at least one step or exactly one step, or at least two steps or exactly two steps in the doping profile characteristic.
[0043] In another embodiment, in the case of only one step, the dopant concentration at the top surface of the step is a factor of 2 greater, or a factor of 5 greater, or a factor of 8 greater than the dopant concentration in the drift layer adjacent the second region.
[0044] A jump transition in the dopant concentration of the first section, i.e., 8×10 15 cm -3 By avoiding a rise in the dopant concentration of 1000 .mu.m by a gradual or stepwise rise through the transition region, ie the second section, the switch-off behavior of the diode in particular is significantly improved.
[0045] The second section has in the first embodiment a layer thickness of at least 0.5 μm and at most 10 μm. Preferably, the second section of the cathode layer has a layer thickness of 3 μm to 5 μm, while the second section of the anode layer has a layer thickness of preferably 2 μm to 4 μm.
[0046] In another refinement, the cathode or anode layer is configured as a substrate. A typical layer thickness of an anode or cathode layer configured as a substrate is between 100 μm and 250 μm.
[0047] The invention will now be described in more detail with reference to the drawings, in which like elements are given the same reference numerals, and in which the illustrated embodiments are very schematic, i.e. the spacings and the lateral and longitudinal extensions are not to scale and have no derivable geometrical relationship to one another, unless otherwise indicated. [Brief description of the drawings]
[0048] [Figure 1] 1 is a diagram showing a first embodiment of a stacked III-V semiconductor diode. [Diagram 2] FIG. 2 is a diagram showing a second embodiment of a stacked III-V semiconductor diode. [Diagram 3] FIG. 13 is a diagram showing a third embodiment of a stacked III-V semiconductor diode. [Figure 4]FIG. 13 illustrates a dopant concentration profile along a stacked III-V semiconductor diode in accordance with another embodiment. [Diagram 5] FIG. 2 illustrates another embodiment of a dopant concentration profile along a stacked III-V semiconductor diode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] In Figure 1, a diagram of a first embodiment of a stacked III-V semiconductor diode 10 is shown, comprising or consisting of GaAs. A heavily n-doped substrate layer constitutes the cathode layer 12, on which a total thickness D O A drift region 14 having a layer thickness D A A highly p-doped anode layer 16 having a
[0050] The drift region 14 has a layer thickness D n a weakly n-doped drift layer 14.1 adjacent to the cathode layer 12, having a thickness D p and a weakly p-doped drift layer 14.2 disposed between the n-doped drift layer 14.1 having a n-doped conductivity type and the anode layer 16.
[0051] Accordingly, the cathode layer 12 constituted by the substrate has a somewhat larger layer thickness D of 50 μm to 250 μm. K The dopant concentration of the cathode layer is preferably at least 8×10 18 cm -3 and is constant or at least substantially constant along the layer thickness.
[0052] The further layer is preferably epitaxially grown on the cathode layer 12. The doping can be produced during epitaxy or by subsequent ion implantation. The layer thickness D of the n-doped drift layer 14.1 nThe dopant concentration is at most 8×10 10 20 μm from the dopant concentration maximum in the direction towards the p-doped drift layer 14.2. 15 cm -3 , preferably at most 2×10 15 cm -3 is reduced by
[0053] The thickness D of the p-doped drift layer 14.2 p is at least 5 μm, preferably at least 20 μm. p is the thickness D of the n-doped drift layer 14.1 n The dopant concentration of the p-doped drift layer 14.2 is at least 1×10 3 , except for the dopant concentration maximum, in the direction toward the anode layer 16. 17 cm -3 , or at least 1 × 10 18 cm -3 is increased by
[0054] Another embodiment is shown in Figure 2. In the following, only the differences from Figure 1 will be described.
[0055] The stacked III-V semiconductor diode 10 has a capacitance of at least 1×10 18 cm -3 A constant dopant concentration of at least 8×10 18 cm -3 The cathode layer 12 comprises a first section 12.1 having a constant dopant concentration of 0.5 μm and a second section 12.2. The second section 12.2 is arranged between the first section 12.1 and the drift region 14 and has a relatively small layer thickness D of 0.5 μm to 10 μm. K2 , preferably a relatively small layer thickness D of 3 μm to 5 μm K2 has.
[0056] The second layer section is used to form a dopant concentration transition from the highly doped first section 12.1 of the cathode layer to the lightly n-doped drift layer 14.1. For this purpose, the second section 12.2 has a dopant concentration profile that rises in the direction towards the first section 12.1 from a dopant concentration minimum to a dopant concentration maximum. The dopant concentration profile is configured linearly, concavely, convexly or stepped with one or more steps. In a stepped profile, preferably one or more or all step edges are configured convexly, concavely or linearly.
[0057] In the first embodiment, the dopant concentration maximum of the second section 12.2 corresponds to the dopant concentration of the first section 12.1, while the dopant concentration minimum of the second section 12.2 corresponds to the dopant concentration maximum of the n-doped drift region. In another embodiment, a dopant concentration jump is configured at the interface between the first section 12.1 and the second section 12.2 and / or between the second section 12.2 and the drift region 14, and the dopant concentration jump is smaller based on the dopant concentration profile of the second section 12.2 than in an embodiment of the semiconductor diode 10 without the second cathode section 12.2.
[0058] Yet another embodiment is shown in Figure 3. In the following, only the differences from Figure 2 will be described.
[0059] The stacked III-V semiconductor diode 10 has a capacitance of at least 1×10 17 cm -3 A first section 16.1 having a constant dopant concentration of 0.5 μm to 10 μm, a dopant concentration profile increasing in the direction towards the first section 16.1 and a layer thickness D of 0.5 μm to 10 μm. A2 , preferably a layer thickness D of 2 μm to 4 μm A2 and a second section 16.2 having a first anode layer 16.3.
[0060] Similar to the second section 12.2 of the cathode layer 12, the second section 16.2 of the anode layer 16 is used to form a dopant concentration transition. The dopant concentration profile of the second section 16.2 is configured to be linear, concave, convex, or stepped with one or more steps. In a stepped profile, preferably one or more or all step edges are configured to be convex, concave or linear.
[0061] In yet another embodiment not shown in this specification, the stacked III-V semiconductor diode 10 has the aforementioned anode layer 16 with two sections 16.1, 16.2 and the drift region 14 shown in the first example of FIG. 1, but does not have the second section 12.2.
[0062] (FIG. 4 shows yet another embodiment. In the following, only the differences from FIG. 1 will be described.)
[0063] Figure 4 shows different dopant concentration profiles along a stacked III-V semiconductor diode 10 with a layer sequence corresponding to the embodiment of Figure 1. The dopant concentration profile of the n-doped drift layer 14.1 extends in alternative embodiments in a convex, concave or linearly increasing manner in the direction towards the cathode layer 12.
[0064] The dopant concentration profile of the p-doped drift layer 14.2 may, in alternative embodiments, extend constant or increasing in the direction towards the anode layer 16, with the increasing portion being configured as a step, convex, linear or concave.
[0065] The convex rise of the n-doped drift layer 14.1 and / or the p-doped drift layer 14.2 is configured in a Gaussian manner in the first embodiment.
[0066] Alternatively, the concave rising portion of the n-doped drift layer 14.1 and / or the p-doped drift layer 14.2 extends according to an exponential curve in one embodiment.
[0067] Yet another embodiment is shown in Figure 5. In the following, only the differences from Figure 4 will be described.
[0068] FIG. 5 illustrates an exemplary profile of different dopant concentrations along a stacked III-V semiconductor diode 10. As shown in FIG.
[0069] The dopant concentration profile starts with a constant high dopant concentration of n-type dopant for the first section 12.1 of the cathode layer 12, followed by a dopant concentration decrease for the second section 12.2 of the cathode layer, which is configured convexly and starts at or substantially lower than the dopant concentration level of the first section 12.1.
[0070] Following this, the dopant concentration for the n-doped drift layer 14.1 drops further, this drop being more gradual and occurring with or without a step.
[0071] An alternation of dopants occurs between the n-doped drift layer 14.1 and the p-doped drift layer 14.2, which in the illustrated embodiment has a constant or linearly increasing or stepped p-type dopant concentration.
[0072] In the second section 16.2 of the anode layer 16 adjacent to the drift region, the dopant concentration of the p-type dopant increases stepwise through a number of rectangularly arranged steps. The adjacent first section 16.1 of the anode layer 16 has a dopant concentration of at least 1×10 17 cm -3 3. The dopant concentration level is 0.01 to 0.1.
[0073] In addition, the anode layer 16 has a third section 16.3 following the first section 16.1, such that the first section 16.1 is disposed between the second section 16.2 and the third section 16.3. The third section 16.3 has a higher dopant concentration than the first section 16.1, preferably at least 5×10 18 cm -3 or at least 1×10 19 cm -3 3. The dopant concentration is constant.
Claims
1. A stacked III-V semiconductor diode (10) containing or made of GaAs, the stacked III-V semiconductor diode (10) comprising: a highly n-doped cathode layer (12); a highly p-doped anode layer (16); a drift region (14) disposed between the cathode layer (12) and the anode layer (16); having The drift region (14) comprises a lightly n-doped drift layer (14.1) and a lightly p-doped drift layer (14.2), In a stacked III-V semiconductor diode (10), the n-doped drift layer (14.1) is disposed between the p-doped drift layer (14.2) and the cathode layer (12), Both drift layers (14.1, 14.2) each have a layer thickness (D ｎ , D ｐ ) and the respective layer thicknesses (D ｎ , D ｐ ) along the maximum of 8 x 10 １５ cm －３ and a dopant concentration maximum of the dopant concentration maxima of both drift layers (14.1, 14.2) relative to each other have a ratio of 0.1 to 10; The thickness (D ｐ ) versus the thickness (D ｎ ) is from 0.5 to 3; the anode layer (16) has a first section (16.1) with a constant dopant concentration profile and a second section (16.2) arranged between the first section (16.1) and the drift region (14) with a dopant concentration profile that increases in the direction towards the first section (16.1), The second section (16.2) has a layer thickness (D Ｋ２ , D Ａ２ ) - isoelectronic or equivalent electron centres are provided in the p-doped drift layer (14.2) and / or the anode layer (16) to improve switching speed; the anode layer (16) has a dopant concentration of at least 1×10 17 cm −3 ; A stacked III-V semiconductor diode (10).
2. The thickness (D ｎ ) is the thickness (D ｐ ) is greater than The stacked III-V semiconductor diode (10) of claim 1.
3. The n-doped drift layer (14.1) and / or the p-doped drift layer (14.2) have a layer thickness (D ｎ , D ｐ ) A stacked III-V semiconductor diode (10) according to claim 1 or 2.
4. The n-doped drift layer (14.1) has a thickness (D ｎ ) in the direction towards the cathode layer (12) up to the dopant concentration maximum value, and the p-doped drift layer (14.2) has a dopant concentration profile along the layer thickness (D ｐ ) along the anode layer (16) to the dopant concentration maximum in a direction toward the anode layer (16). A stacked III-V semiconductor diode (10) according to any one of claims 1 to 3.
5. the increasing dopant concentration profile is linear and / or concave and / or convex and / or has one or more steps; The stacked III-V semiconductor diode (10) of claim 4.
6. The dopant concentration profile of each of the drift layers (14.1, 14.2) is 9×10 １４ cm －３ falls to a value less than A stacked III-V semiconductor diode (10) according to any one of claims 1 to 5.
7. The cathode layer (12) and / or the anode layer (16) have a layer thickness (D Ｋ , D Ａ ) A stacked III-V semiconductor diode (10) according to any one of claims 1 to 6.
8. The second section (16.2) of the anode layer (16) is disposed between the first section (16.1) and the drift region (14) and has a linear and / or concave and / or step-like increasing dopant concentration profile in a direction toward the first section (16.1). A stacked III-V semiconductor diode (10) according to any one of claims 1 to 7.
9. The second section (16.2) has a layer thickness (D Ｋ２ , D Ａ２ ) The stacked III-V semiconductor diode (10) of claim 8.
10. the concentration of the isoelectronic centers is a factor of 1000 to 10 lower than the dopant concentration of the drift layer or the anode layer, respectively; The stacked III-V semiconductor diode (10) of claim 1.
11. the concentration of the isoelectronic centers is a factor of 100 to 20 lower than the dopant concentration in the respective regions of the drift layer or the anode layer; The stacked III-V semiconductor diode (10) of claim 1.
12. the dopant concentration of the p-doped drift layer (14.2) decreases more slowly than the dopant concentration of the second section (16.2) of the anode layer (16); A stacked III-V semiconductor diode (10) according to any one of claims 1 to 11.