Stacked III-V semiconductor diode

Abstract

A semiconductor having a n-doped cathode layer, a p-doped anode layer, and a drift region, arranged between the cathode layer and the anode layer, with a dopant concentration of at most 8.Math.10.sup.15 cm.sup.−3. The drift region has a lightly n-doped drift layer and a lightly p-doped drift layer, arranged between the n-doped drift layer and the anode layer, both drift layers each have a layer thickness of at least 5 μm. The cathode layer has a first section with a dopant concentration of at least 1.Math.10.sup.17 cm.sup.−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 dopant concentration gradient that increases in the direction of the first section up to a dopant concentration maximum. The dopant concentration maximum is smaller or equal to the dopant concentration of the first section.

Claims

1. A stacked semiconductor diode comprising or consisting of GaAs, and comprising: a heavily n-doped cathode layer; a heavily p-doped anode layer; and a drift region arranged between the cathode layer and the anode layer with a dopant concentration of at most 8.Math.10.sup.15 cm.sup.−3, wherein the drift region has a lightly n-doped drift layer and a lightly p-doped drift layer arranged between the n-doped drift layer and the anode layer, wherein both drift layers each have a layer thickness of at least 5 μm, wherein the cathode layer has a first section with a constant or at least substantially constant dopant concentration of at least 1.Math.10.sup.17 cm.sup.−3 or at least 1.Math.10.sup.18 cm.sup.−3 and a second section arranged between the first section and the drift region, wherein the second section has a layer thickness of at least 1 μm and a dopant concentration gradient that increases in the direction of the first section up to a dopant concentration maximum, and wherein the dopant concentration maximum is less than or equal to the dopant concentration of the first section.

2. The stacked semiconductor diode according to claim 1, wherein the anode layer has a first section with a dopant concentration of at least 1.Math.10.sup.17 cm.sup.−3 and a second section arranged between the first section and the drift region, wherein the second section has a layer thickness of at least 1 μm and a dopant concentration gradient that increases in the direction of the first section up to a dopant concentration maximum and the dopant concentration maximum is less than or equal to the dopant concentration of the first section.

3. The stacked semiconductor diode according to claim 1, wherein the layer thickness of the second section is at most 7 μm or at most 5 μm or at most 3 μm.

4. The stacked semiconductor diode according to claim 1, wherein the dopant concentration gradient of the second section is formed concave or convex or linear.

5. The stacked semiconductor diode according to claim 1, wherein the respective dopant concentration gradient in the drift layers is formed concave or convex or linear or step-shaped.

6. The stacked semiconductor diode according to claim 1, wherein the dopant concentration gradient of the second section has one step or a plurality of steps.

7. The stacked semiconductor diode according to claim 6, wherein one step or a plurality of steps or each step of the dopant concentration gradient has a convex flank or a concave flank or a linear flank.

8. The stacked semiconductor diode according to claim 6, wherein each step has a depth of at least 0.2 μm or of at least 0.5 μm.

9. The stacked semiconductor diode according to claim 6, wherein the dopant concentration changes from step to step by at least a factor of 5 or at least a factor of 10.

10. The stacked semiconductor diode according to claim 1, wherein the dopant concentration of the first section of the cathode layer is at least 8.Math.10.sup.18 cm.sup.−3 or at least 1.Math.10.sup.19 cm.sup.−3.

11. The stacked semiconductor diode according to claim 1, wherein the anode layer has a third section, wherein the third section is arranged on a side of the first section that faces away from the second section, and has a dopant concentration of at least 5.Math.10.sup.18 cm.sup.−3 or at least 1.Math.10.sup.19 cm.sup.−3.

12. The stacked semiconductor diode according to claim 1, wherein the cathode layer and/or the anode layer have a layer thickness of at least 2 μm or at least 5 μm or at least 20 μm.

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

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 a dopant concentration gradient along the III-V layer stack of the semiconductor diode;

(4) FIG. 3 is a view of an example of a dopant concentration gradient along the III-V layer stack of the semiconductor diode;

(5) FIG. 4 is a view of an example of a dopant concentration gradient along the III-V layer stack of the semiconductor diode; and

(6) FIG. 5 is a view of an example of a dopant concentration gradient along the III-V layer stack of the semiconductor diode.

DETAILED DESCRIPTION

(7) The illustration in FIG. 1 shows an example of a stacked III-V semiconductor diode 10 comprising GaAs or consisting of GaAs. Semiconductor diode 10 has a cathode layer 12, a drift region 14, and an anode layer 16 with a layer thickness DA in the order mentioned.

(8) Cathode layer 12 has a first section 12.1 formed from a heavily n-doped substrate layer with a layer thickness D.sub.K1 from 50 μm to 250 μm and a constant or at least substantially 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.

(9) In addition, cathode layer 12 has a second section 12.2, which is arranged between first section 12.1 and drift region 14, with a significantly lower layer thickness D.sub.K2 of at least 1 μm. The dopant concentration of an n-dopant of second section 12.2 increases in the direction of first section 12.1 up to a dopant concentration maximum, wherein the dopant concentration maximum is less than the dopant concentration of first section 12.1.

(10) Drift region 14 divides into a weakly n-doped drift layer 14.1, adjacent to the cathode layer 12 and having a layer thickness D.sub.n, 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 anode layer 16.

(11) 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 decreases from a dopant concentration maximum of at most 8.Math.10.sup.15 cm.sup.−3, preferably of at most 2.Math.10.sup.15 cm.sup.−3, in the direction of the p-doped drift layer 14.2.

(12) The layer thickness D.sub.p of the p-doped drift layer 14.2 is at least 5 μm, preferably at least 20 μm. The layer thickness D.sub.p of the p-doped drift layer 14.2 constitutes half or a 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 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.

(13) Starting from the substrate forming first section 12.1 of cathode layer 12, the further layers are preferably produced epitaxially.

(14) The illustration in FIG. 2 shows a first embodiment of the dopant concentration gradient along the stacked III-V semiconductor diode 10 in FIG. 1.

(15) The dopant concentration gradient D is shown versus a position x along the stack of semiconductor diode 10.

(16) Starting from a high and constant n-doping along first section 12.1 of cathode layer 12, the dopant concentration of the n-dopants decreases along second section 12.2 and along n-drift layer 14.1. The decrease is formed convex in each case and takes place considerably more slowly in the region of n-drift layer 14.1 than in the area of second section 12.2 of cathode layer 12.

(17) The PN junction forms between the n-doped drift layer 14.1 and the p-doped drift layer 14.2. In the exemplary embodiment shown, the p-doped drift layer 14.2 has a constant or step-shaped, very low dopant concentration of p-dopants. The subsequent anode layer has a constant and very high dopant concentration of p-dopants.

(18) In the diagram in FIG. 3, a further embodiment of III-V semiconductor diode 10 is shown using the dopant concentration gradient. Only the differences from FIG. 2 will be described below.

(19) The drop in the dopant concentration of second section 12.2 of cathode layer 12 has two steps, each with a convex flank.

(20) The dopant concentration gradient of the n-doped drift layer 14.1 increases in the direction of cathode layer 12 in a convex or linear or concave manner. The dopant concentration gradient of the p-doped drift layer 14.2 also increases in the direction of anode layer 16 in a convex or linear or concave manner.

(21) In addition, the anode layer has a first section 16.1 with a first constant dopant concentration, a second section 16.2, arranged between first section 16.1 and drift region 14, with a dopant concentration gradient increasing over two steps in the direction of the first section 16.1, and a third section 16.3. Third section 16.3 is arranged on the side of first section 16.1 that faces away from second section 16.2 and has a constant dopant concentration, wherein the dopant concentration of third section 16.3 is higher than the dopant concentration of first section 16.1.

(22) In the diagram in FIG. 4, a further embodiment of III-V semiconductor diode 10 is shown using the dopant concentration gradient. Only the differences from FIG. 3 will be described below.

(23) In the embodiment shown, only second section 16.2 of anode layer 16 has a stepped gradient, whereas the increase in the dopant concentration of second section 12.2 of cathode layer 12 is convex.

(24) In the diagram in FIG. 5, a further embodiment of III-V semiconductor diode 10 is shown using the dopant concentration gradient. Only the differences from FIG. 4 will be described below.

(25) The dopant concentration gradient of second section 12.2 of cathode layer 12 increases up to a dopant concentration maximum, wherein the dopant concentration maximum is considerably lower than the dopant concentration of first section 12.1, so that a dopant concentration jump is formed between first section 12.1 and second section 12.2.

(26) In one embodiment shown, the dopant concentration gradient has two steps, each with a convex flank, along the n-doped drift layer.

(27) Along second section 16.2 of anode layer 16, the dopant concentration increases over a number of steps, each with a linear flank, in particular over rectangular steps. In the exemplary embodiment shown, cathode layer 16 does not have a third section 16.3.

(28) 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.