Stacked III-V semiconductor diode

Abstract

To provide a III-V semiconductor diode.SOLUTION: A stacked III-V semiconductor diode 10 containing GaAs comprises: a high-concentration cathode layer 12, a high-concentration anode layer 16, and a drift region 14 arranged between the cathode layer and the anode layer and having a concentration of 8×1015 cm-3 at maximum. The drift region includes a low-concentration n-type drift layer 14.1 and a low-concentration p-type drift layer 14.2. Each of both drift layers has a layer thickness of at least 5 μm. The cathode layer includes a first section having a doping material concentration of at least 1×1017 cm-3 and a second section arranged between the first section and the drift region. The second section has a layer thickness of at least 1 μm and a doping material concentration transition which increases to the maximum value of the doping material concentration in a first section direction. The maximum value of the doping material concentration is less than or equal to the doping material concentration of the first section.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laminated III-V semiconductor diode containing or consisting of GaAs, the laminated III-V semiconductor diode having a cathode layer highly doped with n, an anode layer highly doped with p, and a drift region disposed between the cathode layer and the anode layer.

Background Art

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

[0003] From European Patent No. 3321971 and European Patent No. 3321970, further laminated III-V semiconductor diodes are known, which have an additional intermediate layer between the drift region and the cathode or anode.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Based on the above background, the problem of the present invention is to present an apparatus that develops the prior art.

Means for Solving the Problems

[0005] The above problems are solved by a laminated III-V semiconductor diode having the features described in claim 1. Advantageous embodiments of the present invention are the subject of the dependent claims.

[0006] The object of the present invention is a stacked III-V semiconductor diode comprising or consisting of GaAs, the stacked III-V semiconductor diode comprising a cathode layer highly doped with n-type dopants, an anode layer highly doped with p-type dopants, and a drift region arranged between the cathode layer and the anode layer and having a doping material concentration of up to 8·10 15 cm -3 . A stacked III-V semiconductor diode is provided.

[0007] The drift region has a drift layer lightly doped with n-type dopants and a drift layer lightly doped with p-type dopants arranged between the n-doped drift layer and the anode layer, both drift layers having a layer thickness of at least 5 μm each.

[0008] The cathode layer has a first section having a constant or at least substantially constant doping material concentration of at least 1·10 17 cm -3 or at least 1·10 18 cm -3 , and a second section arranged between the first section and the drift region.

[0009] The second section has a layer thickness of at least 1 μm and a doping material concentration profile increasing to a maximum doping material concentration in the direction of the first section.

[0010] The maximum doping material concentration is below the doping material concentration of the first section.

[0011] It goes without saying that all semiconductor layers of the semiconductor diode made of or comprising GaAs, namely, in particular, the cathode layer, the anode layer and the drift region, are each made of GaAs or at least comprise GaAs. In other words, each semiconductor layer of the III-V semiconductor diode has at least the elements Ga and As.

[0012] The semiconductor layer is preferably produced by epitaxy. In one development form, the cathode layer or the anode layer can be formed by the substrate layer. Preferably, in order to form a III-V semiconductor diode, further III-V semiconductor layers are epitaxially grown on the substrate layer.

[0013] Alternatively, the III-V semiconductor diode includes at least one semiconductor junction. In this case, the surfaces of two GaAs semiconductor disks or GaAs wafers are joined together.

[0014] Preferably, the doping of each GaAs semiconductor layer is introduced during epitaxy. Preferably, the epitaxy is carried out by MOVPE and / or LPE.

[0015] In one development form, doping by ion implantation is carried out additionally after epitaxial growth or, alternatively, instead of being introduced during epitaxy.

[0016] Furthermore, it is self-evident that the semiconductor diode preferably has a further layer made of other materials, in particular a terminal contact layer made of metal. The terminal contact layer is formed, for example, entirely or partially from a metal, such as gold or a metal alloy, and is produced, for example, by electron beam evaporation or sputtering.

[0017] At least the regions of the cathode layer and the anode layer adjacent to the terminal contact layer preferably have a high doping material concentration in order to form a contact with as low an ohmic resistance as possible and to keep the series resistance or the power loss of the semiconductor diode as low as possible.

[0018] The drift region is characterized by an overall width of at least 10 μm and being divided into two regions or layers with different dopings of low concentration.

[0019] Preferably, the overall width is at least 20 μm or at least 40 μm or at least 60 μm. The overall width is divided into a region or layer doped with p at a low concentration and a region or layer doped with n at a low concentration.

[0020] Accordingly, the pn junction is formed inside the drift region and within a region having a very low doping material concentration.

[0021] A transition is formed between the drift region and the high doping material concentration level of the first section of the cathode by means of a second cathode section having a doping material concentration profile increasing in the direction of the first cathode section.

[0022] By the doping material concentration in the transition region increasing stepwise over one, two or more steps, it becomes possible to manufacture a diode having significantly improved turn-off behavior. The variation of the current-voltage characteristic curve when switching off the diode is minimized.

[0023] A further advantage is that a small switching-on resistance and a particularly low capacitance per area can be achieved by means of a diode having a particularly high reverse voltage exceeding 1100 V or rather 1200 V.

[0024] In one development, isocenters or equivalent centers are incorporated into the p-doped drift layer and / or anode layer in order to increase the switching speed, i.e. the switching between the reverse and forward directions.

[0025] In particular, it is possible to manufacture a diode having a reverse recovery charge of up to 800 nC.

[0026] In a first development, the anode layer is at least 1·10 17 cm -3It has a first section having a doping material concentration, and a second section disposed between the first section and the drift region.

[0027] The second section has a layer thickness of at least 1 μm and a doping material concentration profile that increases to a maximum doping material concentration in the direction of the first section.

[0028] The maximum doping material concentration of the second section is equal to or less than the doping material concentration of the first section.

[0029] The second layer section of the anode layer is configured such that the transition of the doping material concentration between the drift region and the further anode layer increases stepwise or continuously.

[0030] In one embodiment, the layer thickness of the second section of the cathode layer and / or the anode layer is at most 7 μm or at most 5 μm or at most 3 μm. For example, a small layer thickness is sufficient to improve the switching-off behavior of the diode without unnecessarily increasing the series resistance.

[0031] In other embodiments, the doping material concentration profile of the second section of the cathode layer and / or the anode layer is configured to be concave or convex or linear.

[0032] In a further embodiment, the doping material concentration profile of the second section of the cathode layer and / or the anode layer has one or more steps, and in an alternative development, one or more steps of the doping material concentration profile or each step has a convex edge or a concave edge or a linear edge.

[0033] In a further development, each step has a depth of at least 0.2 μm or at least 0.5 μm.

[0034] In other embodiments, the doping material concentration changes by at least a factor of 5 or at least a factor of 10 for each step.

[0035] In a further embodiment, the doping material concentration in the first section of the cathode layer is at least 8·10 18 cm -3 or at least 1·10 19 cm -3 .

[0036] In another development, the anode layer has a third section, the third section being arranged on the side of the first section facing away from the second section, and having a doping material concentration of at least 5·10 18 cm -3 or at least 1·10 19 cm -3 .

[0037] By dividing the anode layer into two sub-layers, it is possible to minimize the ohmic resistance with the terminal contact part by means of high-concentration doping, and at the same time, it is possible to realize the potential gradient between the cathode layer and the anode layer by doping at a slightly lower concentration in the vicinity adjacent to the drift region, and it is possible to further improve the turn-off behavior.

[0038] In a further development, the cathode layer and / or the anode layer has a layer thickness of at least 2 μm or at least 5 μm or at least 20 μm.

[0039] In another embodiment, the cathode layer or the anode layer is formed as a substrate.

[0040] In one development, the respective doping material concentration profile in the drift layer is configured in a concave or convex or linear or stepped manner.

[0041] Hereinafter, the present invention will be described in more detail with reference to the drawings. In the drawings, the same reference numerals are assigned to the same parts. The illustrated embodiments are very schematic, that is, the distances and the extensions in the lateral and vertical directions are not to scale and do not have geometric relationships that can be derived from each other without further description.

Brief Description of the Drawings

[0042]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0043] The drawing of FIG. 1 shows a first embodiment of a laminated III-V semiconductor diode 10 having or consisting of GaAs. The semiconductor diode 10 has a cathode layer 12, a drift region 14, and an anode layer 16 having a layer thickness D A in the described order.

[0044] The cathode layer 12 has a layer thickness D of 50 μm to 250 μm K1 and at least 1·10 18 cm -3 and preferably at least 8·10 18 cm -3It has a first section 12.1 formed from a highly doped substrate layer having a constant or at least substantially constant doping material concentration and being n-doped at a high concentration.

[0045] Furthermore, the cathode layer 12 has a second section 12.2, which is arranged between the first section 12.1 and the drift region 14 and has a significantly thinner layer thickness D of at least 1 μm. K2 The doping material concentration of the n-doping material in the second section 12.2 increases to a maximum doping material concentration in the direction of the first section 12.2. This maximum doping material concentration is lower than the doping material concentration of the first section 12.1.

[0046] The drift region 14 is adjacent to the cathode layer 12 and has a low-concentration n-doped drift layer 14.1 with a layer thickness D. n It is divided into a low-concentration p-doped drift layer 14.2 with a thickness D, which is arranged between the n-doped drift layer 14.1 and the anode layer 16. p

[0047] The layer thickness D of the n-doped drift layer 14.1 n is at least 5 μm, preferably at least 40 μm. The doping material concentration decreases in the direction of the p-doped drift layer 14.2 from a maximum doping material concentration of up to 8·10 15 cm -3 , preferably up to 2·10 15 cm -3 .

[0048] The layer thickness D of the p-doped drift layer 14.2 p is at least 5 μm, preferably at least 20 μm. Preferably, the layer thickness D of the p-doped drift layer 14.2 p is half or one-third of the layer thickness D of the n-doped drift layer 14.1. The doping material concentration of the p-doped drift layer 14.2 is at least 1·10 n cm 17 in the direction of the anode layer 16.-3 or at least 1·10 18 cm -3 and increases up to a maximum doping material concentration of

[0049] Starting from the substrate forming the first section 12.1 of the cathode layer 12, further layers are preferably generated epitaxially.

[0050] The drawing of FIG. 2 shows a first embodiment of the doping material concentration profile along the stacked III-V semiconductor diode 10 of FIG. 1.

[0051] The doping material concentration profile D is shown over the position x along the stack of the semiconductor diode 10.

[0052] Starting from a high-concentration constant n-doping along the first section 12.1 of the cathode layer 12, the doping material concentration of the n-doping material decreases along the second section 12.2 and along the n-drift layer 12. This decrease is configured convexly in each case, and in the region of the n-drift layer 14.1, it occurs much more slowly than in the region of the second section 12.2 of the cathode layer 12.

[0053] The pn junction is formed between the n-doped drift layer 14.1 and the p-doped drift layer 14.2. The p-doped drift layer 14.2 has a p-doping material with a constant or stepped very low doping material concentration in the illustrated embodiment. The adjacent anode layer has a constant very high concentration of p-type doping material.

[0054] The drawing of FIG. 3 shows a further embodiment of the III-V semiconductor diode 10 based on the doping material concentration profile. Only the differences from FIG. 2 are shown below.

[0055] The decrease in the doping material concentration in the second section 12.2 of the cathode layer 12 has two steps each with a convex edge.

[0056] The doping material concentration profile of the n-doped drift layer 14.1 increases convexly or linearly or concavely in the direction of the cathode layer 12. The doping material concentration profile of the p-doped drift layer 14.2 also increases convexly or linearly or concavely in the direction of the anode layer 16.

[0057] Furthermore, the anode layer has a first section 16.1 having a first constant doping material concentration, a second section 16.2 disposed between the first section 16.1 and the drift region 14 and having a doping material concentration profile that increases over two steps in the direction of the first section, and a third section 16.3. The third section 16.3 is disposed on the side of the first section 16.1 opposite to the second section 16.2 and has a constant doping material concentration, and the doping material concentration of the third section 16.3 is higher than the doping material concentration of the first section 16.1.

[0058] The drawing of FIG. 4 shows a further embodiment of the III-V semiconductor diode 10 based on the doping material concentration profile. Only the differences from FIG. 3 are shown below.

[0059] In the illustrated embodiment, only the second section 16.2 of the anode layer 16 has a stepped profile, while the increase in the doping material concentration of the second section 12.2 of the cathode layer 12 is convex.

[0060] The drawing of FIG. 5 shows a further embodiment of the III-V semiconductor diode 10 based on the doping material concentration profile. Only the differences from FIG. 4 are shown below.

[0061] The doping material concentration profile of the second section 12.2 of the cathode layer 12 increases to the maximum doping material concentration, and this maximum doping material concentration is significantly lower than the doping material concentration of the first section 12.1. Thus, a sharp change in the doping material concentration is formed between the first section 12.1 and the second section 12.2.

[0062] In the illustrated embodiment, along the n-doped drift layer, the doping material concentration profile has two steps each having a convex edge.

[0063] Along the second section 16.2 of the anode layer 16, the doping material concentration increases over a plurality of steps each having a linear edge, in particular over steps configured in a rectangular shape. In the illustrated example, the anode layer 16 does not have a third section 16.3.

Claims

1. A laminated semiconductor diode (10) containing GaAs or consisting of GaAs, wherein the laminated semiconductor diode (10) is · a cathode layer (12) doped with n-type at a high concentration, and · an anode layer (16) doped with p-type at a high concentration,[[]] ・A drift region (14) having a doping material concentration of up to 8·10 １５ cm －３ is disposed between the cathode layer (12) and the anode layer (16), and and has · the drift region (14) has a drift layer (14.1) doped with n-type at a low concentration and a drift layer (14.2) doped with p-type at a low concentration disposed between the n-doped drift layer (14.1) and the anode layer (16); · both of the drift layers each have a layer thickness of at least 5 μm; - The cathode layer (12) has a first section (12.1) having a constant doping material concentration of at least 1·10 １７ cm －３ and a second section (12.2) disposed between the first section (12.1) and the drift region (14). ・The second section (12.2) has a layer thickness (D) of at least 1 μm Ｋ２ and a doping material concentration profile that increases to a maximum doping material concentration in the direction of the first section (12.1). · the maximum value of the doping material concentration is equal to or less than the doping material concentration of the first section (12.1); the layer thickness (DK2) of the second section (12.2) is at most 7 μm; in the region of the n-doped drift layer (14.1), the doping material concentration decreases more slowly than in the region of the second section (12.2) of the cathode layer (12); A laminated semiconductor diode (10).

2. The n-doped drift layer and the p-doped drift layer have an overall width of at least 40 μm.[[]] The laminated semiconductor diode (10) according to Claim 1.[[]]

3. The layer thickness (DK2) of the second section (12.2) is at most 5 μm.[[]] The laminated semiconductor diode (10) according to Claim 1 or 2.[[]]

4. The doping material concentration profile of the second section (12.2) is configured to be concave, convex, or linear.[[]] The laminated semiconductor diode (10) according to any one of Claims 1 to 3.[[]]

5. The doping material concentration profile in each of the drift layers (14.1, 14.2) is configured to be concave, convex, linear, or stepped.[[]] The laminated semiconductor diode (10) according to any one of Claims 1 to 4.[[]]

6. The doping material concentration profile of the second section (12.2) has one or more steps.[[]] The laminated semiconductor diode (10) according to any one of Claims 1 to 5.[[]]

7. Each step has a depth of at least 0. ​ ​ ​ The laminated semiconductor diode (10) according to claim 6 or 7.

9. The doping material concentration of the first section (12.1) of the cathode layer (12) is at least 8·10 １８ cm －３ is The laminated semiconductor diode (10) according to any one of claims 1 to 8.

10. The cathode layer (12) and / or the anode layer (16) has a layer thickness of at least 2 μm. The laminated semiconductor diode (10) according to any one of claims 1 to 9.

11. The cathode layer (12) or the anode layer (16) is formed as a substrate. The laminated semiconductor diode (10) according to any one of claims 1 to 10.

12. The p-doped drift layer and / or the anode layer has an isoelectric center or an equivalent center. The laminated semiconductor diode (10) according to any one of claims 1 to 11.

13. The anode layer (16) has a first section (16.1) having a doping material concentration of at least 1·10 １７ cm －３ and a second section (16.2) disposed between the first section (16.1) and the drift region (14). The second section (16.2) has a layer thickness (D) of at least 1 μm Ａ２ and a doping material concentration profile that increases to a maximum doping material concentration in the direction of the first section (16.1). The maximum value of the doping material concentration is equal to or less than the doping material concentration in the first section (16.1). The laminated semiconductor diode (10) according to any one of claims 1 to 12.

14. The anode layer (16) has a third section (16.3). The third section (16.3) is arranged on the side of the first section (16.1) facing away from the second section (16.2), and has a doping material concentration of at least 5·10 １８ cm －３ . The laminated semiconductor diode (10) according to claim 13.

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