# US 2023/0411548 A1 · Photoconductor and method for producing same

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- Number: US 2023/0411548 A1
- Document ID: US20230411548A1
- Status: Published application
- Kind: A1
- Application number: 18/035,725
- Filed: 2021-10-22
- Published: 2023-12-21
- Earliest claimed: 2020-11-06
- Assignees: Humboldt-Universitat Zu Berlin; Fraunhofer-Gesellschaft zur Förderung derangewandten Forschung e.V.
- Applicants: Humboldt-Universitat Zu Berlin; Fraunhofer-Gesellschaft Zur Forderung Derangewandten Forschung E.V.
- Inventors: William Ted MASSELINK; Mykhaylo Petrovych SEMTSIV; Bjöm GLOBISCH
- Web page: https://patentgrep.com/patent/US20230411548A1

## CPC

- H10F 30/10: the devices being sensitive to infrared radiation, visible or ultraviolet radiation, and having no potential barriers, e.g. photoresistors
- H10F 71/1272: {comprising at least three elements, e.g. GaAlAs or InGaAsP}
- H10F 77/1243: {characterised by the dopants}
- H10F 77/1248: {having three or more elements, e.g. GaAlAs, InGaAs or InGaAsP}
- H10F 77/146: {Superlattices; Multiple quantum well structures}
- H10F 77/1468: {Doped superlattices, e.g. N-I-P-I superlattices}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

The invention relates inter alia to a photoconductor (10) comprising a multilayer (13) which comprises a plurality of photoconductive semiconductor layers (131-134). According to the invention, the multilayer (13) comprises at least two sublayers (130) which each comprise at least a first photoconductive semiconductor layer (131) and a second photoconductive semiconductor layer (132), wherein the first and the second photoconductive semiconductor layer (131, 132) are doped to different degrees for each of the sublayers (130).

## Claims

### Claim at position 1

1-10. (canceled)

### Claim 11

A photoconductor (10) having a layer package (13) comprising a plurality of photoconductive semiconductor layers (131-134), characterized in that
the layer package (13) comprises at least two sub-packages (130), each comprising at least one first photoconductive semiconductor layer (131) and a second photoconductive semiconductor layer (132),
wherein in each of the sub-packages (130) the first and second photoconductive semiconductor layer (131, 132) are doped to different degrees.

### Claim 12 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein in each of the sub-packages (130), the first photoconductive semiconductor layer (131) is doped at least 10 times higher than the second photoconductive semiconductor layer (132).

### Claim 13 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein the dopant, with which the first and second photoconductive semiconductor layer (131, 132) of each sub-package (130) are differently doped, is a transition metal in each case.

### Claim 14 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein in each of the sub-packages (130)
the dopant in the first photoconductive semiconductor layer (131) forms a higher concentration of dopant clusters than in the second photoconductive semiconductor layer (132) and
the dopant distribution in the second photoconductive semiconductor layer (132) is homogeneous, at least more homogeneous than in the first photoconductive semiconductor layer (131).

### Claim 15 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein in each of the sub-packages (130), due to the different doping
the first photoconductive semiconductor layer (131) in each case has a greater recombination rate for electron-hole pairs than the second photoconductive semiconductor layer (132) and
in each of the sub-packages (130), due to the different doping, the second photoconductive semiconductor layer (132) has a greater electrical resistance than the first photoconductive semiconductor layer (131).

### Claim 16 (depends on 15)

The photoconductor (10) as claimed in claim 15, wherein the dopant or dopants with which the first and second semiconductor layers (131, 132) are doped is or are iron, rhodium or ruthenium.

### Claim 17 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein the thickness of each of the semiconductor layers (131-134) of each sub-package (130) is less than 10 nm in each case.

### Claim 18 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein the thickness of the layer package (13) formed from the sub-packages (130) is in a range between 0.6 and 2 μm.

### Claim 19 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein the number of sub-packages (130) in the layer package (13) is between 20 and 100.

### Claim 20 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein
the thickness of the first and second photoconductive semiconductor layers (131, 132) for each sub-package (130) is on the order of magnitude of the de-Broglie wavelength of electrons located in the respective semiconductor layer (131, 132) and mobile in the respective layer plane, and
the probability distribution of electrons in each sub-package (130)—viewed perpendicular to the layer plane of the semiconductor layers (131-134)—extends at least over the first and second semiconductor layer (131).

### Claim 21 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein in at least one of the sub-packages (130) or in all sub-packages (130), an intermediate layer (133) is arranged between the first and second semiconductor layer (131, 132), which slows down the diffusion of the dopant from the first into the second semiconductor layer.

### Claim 22 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein the first and second semiconductor layers (131, 132) are each doped InGaAs layers.

### Claim 23 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein the dopant or dopants with which the first and second semiconductor layers (131, 132) are doped is or are iron, rhodium or ruthenium.

### Claim 24 (depends on 15)

The photoconductor (10) as claimed in claim 15, wherein the dopant with which the first and second semiconductor layers (131, 132) are doped is iron.

### Claim 25 (depends on 15)

The photoconductor (10) as claimed in claim 15, wherein the dopant with which the first and second semiconductor layers (131, 132) are doped is rhodium.

### Claim 26 (depends on 15)

The photoconductor (10) as claimed in claim 15, wherein the dopant which the first and second semiconductor layers (131, 132) are doped is ruthenium.

### Claim 27 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein an antenna for radiating and receiving terahertz radiation is connected to the photoconductor (10).

### Claim 28 (depends on 11)

The photoconductor (10) as claimed in claim 11, wherein-the first and second semiconductor layers (131, 132) are each molecular beam epitaxy-grown layers and/or
the dopant, with which the first and second photoconductive semiconductor layer (131, 132) of each sub-package (130) are differently doped, is the same transition metal in both the first and second photoconductive semiconductor layer (131, 132) and/or
in at least one sub-package (130), the first photoconductive semiconductor layer (131) is doped with one transition metal and the second photoconductive semiconductor layer (132) is doped with another transition metal and/or
light of a wavelength range between 0.5 μm and 2 μm is absorbed in at least one of the sub-packages (130) and/or
a photoconductive layer, preferably the first or the second semiconductor layer (131, 132) of each sub-package (130), is doped with a transition metal and one or the other photoconductive semiconductor layer (131, 132) of each sub-package (130) is n-doped, p-doped or undoped and/or
at least one of the layers, preferably the first and/or the second photoconductive semiconductor layer (131, 132) of each sub-package (130), is doped with a dopant which is energetically in the region of the band center of the band gap of the semiconductor material of the respective layer, and has a deviation from the band center of a maximum of ±10% of the band gap energy of the band gap.

### Claim 29

A method for producing a photoconductor (10), in which a layer package (13) having a plurality of photoconductive semiconductor layers (131-134) is applied indirectly or directly to a substrate (11), characterized in that
a layer package (13) comprising at least two sub-packages (130) is applied to the substrate (11) or to a buffer layer (12) located on the substrate (11), each comprising at least one first photoconductive semiconductor layer (131) and a second photoconductive semiconductor layer (132),
wherein in each of the sub-packages (130) the first and second photoconductive semiconductor layer (131, 132) are doped to different degrees.

### Claim 30 (depends on 29)

Method of claim 29,
wherein the dopant or dopants with which the first and second semiconductor layers (131, 132) are doped is or are iron, rhodium or ruthenium, and
wherein in each of the sub-packages (130), due to the different doping
the first photoconductive semiconductor layer (131) in each case has a greater recombination rate for electron-hole pairs than the second photoconductive semiconductor layer (132) and
in each of the sub-packages (130), due to the different doping, the second photoconductive semiconductor layer (132) has a greater electrical resistance than the first photoconductive semiconductor layer (131).