Stacked III-V semiconductor diode

Abstract

A stacked III-V semiconductor diode comprising or consisting of GaAs with 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, wherein the drift region has a low n-doped drift layer and a low p-doped drift layer, the n-doped drift layer is arranged between the p-doped drift layer and the cathode layer, both drift layers each have a layer thickness of at least 5 μm and, along the respective layer thickness, have a dopant concentration maximum of not more than 8.Math.10.sup.15 cm.sup.−3, the dopant concentration maxima of the two drift layers have a ratio of 0.1 to 10 to each other and a ratio of the layer thickness of the n-doped drift layer to the layer thickness of the p-doped drift layer is between 0.5 and 3.

Claims

1. A stacked III-V semiconductor diode comprising or consisting of GaAs, and comprising: 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, the drift region having a low n-doped drift layer and a low p-doped drift layer, wherein the n-doped drift layer is arranged between the p-doped drift layer and the cathode layer, wherein both drift layers each have a layer thickness of at least 5 μm and, along the respective layer thickness, a dopant concentration maximum of not more than 8.Math.10.sup.15 cm.sup.−3, wherein the dopant concentration maxima of the two drift layers to each other have a ratio of 0.1 to 10, wherein a ratio of the layer thickness of the n-doped drift layer to the layer thickness of the p-doped drift layer is between 0.5 to 3, and wherein the anode layer and/or the cathode layer has a first section with a constant dopant concentration curve and a second section arranged between the first section and the drift region with a dopant concentration curve ascending in a step-like manner in the direction of the first section.

2. The stacked Ill-V semiconductor diode according to claim 1, wherein the layer thickness of the n-doped drift layer is greater than the layer thickness of the p-doped drift layer.

3. The stacked III-V semiconductor diode according to claim 1, wherein the n-doped drift layer and/or the p-doped drift layer has a layer thickness of at least 20 μm or at least 40 μm.

4. The stacked III-V semiconductor diode according to claim 1, wherein the n-doped drift layer has an ascending dopant concentration curve along the layer thickness in the direction of the cathode layer up to the dopant concentration maximum.

5. The stacked III-V semiconductor diode according to claim 1, wherein the p-doped drift layer has an ascending dopant concentration curve along the layer thickness in the direction of the anode layer up to the dopant concentration maximum.

6. The stacked III-V semiconductor diode according to claim 4, wherein the ascending dopant concentration curve is linear or concave or convex or comprises a plurality of steps.

7. The stacked III-V semiconductor diode according to claim 4, wherein the dopant concentration curve of the n-doped drift layer and/or the p-doped drift layer has one or more steps along the layer thickness.

8. The stacked III-V semiconductor diode according to claim 7, wherein one step or several steps or each step has a convex flank or a concave flank or a linear flank.

9. The stacked Ill-V semiconductor diode according to claim 4, wherein the dopant concentration curve of the two drift layers in the direction of the other drift layer drop to a value less than 9.Math.10.sup.14 cm.sup.−3 or less than 6.Math.10.sup.14 cm.sup.−3 or less than 3.Math.10.sup.14 cm.sup.−3 or less than 2.Math.10.sup.14 cm.sup.−3.

10. The stacked III-V semiconductor diode according to claim 1, wherein the cathode layer and/or the anode layer has a dopant concentration of at least 1.Math.10.sup.17 cm.sup.−3 or at least 5.Math.10.sup.18 cm.sup.−3 or at least 8.Math.10.sup.18 cm.sup.−3.

11. The stacked III-V semiconductor diode according to claim 1, wherein 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.

12. The stacked III-V semiconductor diode according to claim 1, wherein the cathode layer has a first section with a constant dopant concentration curve and a second section arranged between the first section and the drift region with a dopant concentration curve ascending in a linear and/or concave and/or step-like manner in the direction of the first section.

13. The stacked III-V semiconductor diode according to claim 12 wherein the second section has a layer thickness of at least 0.5 μm and of a maximum of 10 μm of at least 2 μm and at most 4 μm.

14. The stacked III-V semiconductor diode according to claim 1, wherein the cathode layer or the anode layer is formed as a substrate.

15. The stacked Ill-V semiconductor diode according to claim 1, wherein the p-doped drift layer and/or the anode layer have isoelectric or isovalent centers to increase the switching speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 is a view of an example of a stacked III-V semiconductor diode,

(3) FIG. 2 is a view of an example of the stacked III-V semiconductor diode,

(4) FIG. 3 is a view of an example of the stacked III-V semiconductor diode,

(5) FIG. 4 is a dopant concentration curve along the stacked III-V semiconductor diode in a further embodiment, and

(6) FIG. 5 is an example of the dopant concentration curve along the stacked II-V semiconductor diode.

DETAILED DESCRIPTION

(7) The illustration of FIG. 1 shows a view of a first embodiment of a stacked III-V semiconductor diode 10 comprising GaAs or consisting of GaAs. A highly n-doped substrate layer forms a cathode layer 12, on which the drift region 14 is arranged with a total thickness D.sub.D, followed by a highly p-doped anode layer 16 with a layer thickness D.sub.A.

(8) The drift region 14 is divided into a weakly n-doped drift layer 14.1 with a layer thickness D.sub.n adjacent to the cathode layer 12 and a weakly p-doped drift layer 14.2 with a layer thickness D.sub.p arranged between the n-doped drift layer 14.1 and the anode layer 16.

(9) The cathode layer 12 formed by a substrate accordingly has a slightly greater layer thickness DK of 50 μm to 250 μm. A dopant concentration of the cathode layer is preferably at least 8.Math.10.sup.18 cm.sup.−3 and is constant or at least substantially constant along the layer thickness.

(10) The other layers are preferably epitaxially produced on the cathode layer 12. The doping can be generated during epitaxy or subsequently by ion implantation. The layer thickness D.sub.n of the n-doped drift layer 14.1 is at least 5 μm, preferably at least 40 μm. A dopant concentration drops from a dopant concentration maximum of not more than 8.Math.10.sup.15 cm.sup.−3, preferably from a maximum of 2.Math.10.sup.15 cm.sup.−3, in the direction of the p-doped drift layer 14.2.

(11) The layer thickness D.sub.p of the p-doped drift layer 14.2 is at least 5 μm, preferably at least 20 μm. Preferably, the layer thickness D.sub.p of the p-doped drift layer 14.2 is half or one third of the layer thickness D.sub.n of the n-doped drift layer 14.1. A dopant concentration of the p-doped drift layer 14.2 increases in the direction of the anode layer 16 up to a dopant concentration maximum of at least 1.Math.10.sup.17 cm.sup.−3 or at least 1.Math.10.sup.18 cm.sup.−3.

(12) In the illustration of FIG. 2, another embodiment is shown. In the following, only the differences to the illustration in FIG. 1 are explained.

(13) The stacked III-V semiconductor diode 10 has a cathode layer 12 with a first section 12.1 having a constant dopant concentration of at least 1.Math.10.sup.18 cm.sup.−3, preferably of at least 8.Math.10.sup.18 cm.sup.−3 and with 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 low layer thickness D.sub.K2 of 0.5 μm to 10 μm, preferably from 3 μm to 5 μm.

(14) The second layer section serves to shape the transition of the dopant concentration from the highly doped first section 12.1 of the cathode layer to the low n-doped drift layer 14.1. The second section 12.2 has for this purpose a dopant concentration curve ascending in the direction of the first section 12.1 from a dopant concentration minimum to a dopant concentration maximum. The dopant concentration curve is linear or concave or convex or stepped with one step or with several steps. In a step-like curve, the flank of one or more steps or of all steps is preferably convex or concave or linearly formed.

(15) In an example, 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 other embodiments, a jump in the dopant concentration is formed at the interface between the first and second sections 12.1, 12.2 and/or between the second section 12.2 and the drift region 14, wherein the jump in the dopant concentration, due to the dopant concentration curve of the second section 12.2, is lower than in an embodiment of the semiconductor diode 10 without the second cathode section 12.2.

(16) In the illustration of FIG. 3, another example is shown. In the following, only the differences to FIG. 2 are explained.

(17) The stacked III-V semiconductor diode 10 has an anode layer 16 with a first section 16.1 with a constant dopant concentration of at least 1.Math.10.sup.17 cm.sup.−3 and a second section 16.2 with a dopant concentration profile ascending in the direction of the first section 16.1 and a layer thickness D.sub.A2 from 0.5 μm to 10 μm, preferably from 2 μm to 4 μm.

(18) Like the second section 12.2 of the cathode layer 12, the second section 16.2 of the anode layer 16 serves to shape the transition of the dopant concentration. The dopant concentration curve of the second section 16.2 is linear or concave or convex or stepped with one or more steps. In a step-like curve, the flank of one or more steps or of all steps is preferably convex or concave or linearly formed.

(19) The stacked III-V semiconductor diode 10 can have the anode layer 16 with the two sections 16.1 and 16.2 and a drift layer 14 described above in the first embodiment of FIG. 1, i.e., without the second section 12.2.

(20) In the illustration of FIG. 4, another example is shown. In the following, only the differences to FIG. 1 are explained.

(21) FIG. 4 shows various dopant concentration curves along the stacked III-V semiconductor diode 10 with a layer sequence corresponding to the embodiment of FIG. 1. In alternative embodiments, the dopant concentration curve of the n-doped drift layer 14.1 proceeds convex or concave or linearly ascending in the direction of the cathode layer 12.

(22) The dopant concentration curve of the p-doped drift layer 14.2 proceeds in the direction of the anode layer 16 in a constant or ascending manner, wherein the ascension is stepped or convex or linear or concave.

(23) The convex rise of the n-doped and/or the p-doped drift layer 14.1 or 14.2 is gauss-shaped.

(24) Alternatively, in an embodiment the concave ascension of the n-doped and/or the p-doped drift layer 14.1 or 14.2 follows an exponential curve.

(25) In the illustration of FIG. 5, another example is shown. In the following, only the differences to the illustration of FIG. 3 are explained.

(26) In FIG. 5, various dopant concentration curves along the stacked III-V semiconductor diode 10 are shown as examples.

(27) The dopant concentration curve begins with a constant, high dopant concentration of n-dopants over the first section 12.1 of the cathode layer 12, followed by a dopant concentration drop over the second section 12.2 of the cathode layer, wherein the drop is convex and begins at the dopant concentration level of the first section 12.2 or at a significantly lower level.

(28) Subsequently, the dopant concentration drops further over the n-doped drift layer 14.1. The drop takes place more slowly and with or without steps.

(29) Between the n-doped drift layer 14.1 and the p-doped drift layer 14.2, a change of the dopant takes place, wherein the p-doped drift layer 14.2 in the embodiment shown has a constant or linearly ascending or stepped concentration of p-dopants.

(30) In the second section 16.2 of the anode layer 16 adjacent to the drift region, the dopant concentration of p-dopants ascends in a step-like manner over several rectangular steps. The subsequent first section 16.1 of the anode layer 16 has a constant dopant concentration level of at least 1.Math.10.sup.17 cm.sup.−3.

(31) In addition, the anode layer 16 has a third section 16.3 following the first section 16.1, so that the first section 16.1 is arranged 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 a constant dopant concentration of at least 5.Math.10.sup.18 cm.sup.−3 or of at least 1.Math.10.sup.19 cm.sup.−3.

(32) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.