Semiconductor structure and method for its production

Abstract

The present invention relates to a semiconductor structure and a method for its production, the semiconductor structure comprising at least one conductor region and at least two semiconductor regions, which semiconductor regions are partly separated by the at least one conductor region. The at least one conductor region comprises openings extending between the semiconductor regions which are partly separated by the respective conductor region. The semiconductor regions comprise at least one organic semiconductor material having a specific HOMO energy level, in particular a DPP polymer. The conductor region comprises a conductive material having a specific work function, said combination of specific energy level and work function allowing for a simple preparation of the conductive region. The invention further relates to a method for providing such a semiconductor structure.

Claims

1. A semiconductor structure, comprising at least one conductor region and at least two semiconductor regions which are partly separated by the at least one conductor region, wherein: the at least one conductor region comprises openings extending between the semiconductor regions; at least one of the semiconductor regions comprises a diketopyrrolopyrrole polymer as semiconductor material; the semiconductor regions comprise at least one organic semiconductor material having a highest occupied molecular orbital energy level E.sub.H defined by:
5.0 eV|E.sub.H|5.8 eV; the conductor region comprises a conductive material having a work function E.sub.C defined by:
|E.sub.H|1.5 eV|E.sub.C||E.sub.H|0.4 eV; and contacts between each of the at least one conductor region and each of the at least one semiconductor region are Schottky contacts.

2. The semiconductor structure of claim 1, wherein a bulk concentration of positive charge carrier equivalents N.sub.p of the organic semiconductor material satisfies:
Np2.310.sup.15 cm.sup.3.

3. The semiconductor structure of claim 2, wherein E.sub.H, E.sub.C, and N.sub.p are adapted to yield a depletion width I.sub.d of more than 100 nm within the semiconductor region.

4. The semiconductor structure of claim 1, wherein the at least one organic semiconductor material comprises a diketopyrrolopyrrole (DPP) polymer having one or more DPP skeletons represented by the following formula: ##STR00032## in the repeating unit, wherein: R.sup.1 and R.sup.2 are the same or different from each other and are selected from the group consisting of hydrogen; a C.sub.1-C.sub.100 alkyl group; COORS; a C.sub.1-C.sub.100 alkyl group which is substituted by one or more halogen atoms, hydroxyl groups, nitro groups, CN, or C.sub.6-C.sub.18 aryl groups and/or interrupted by O, COO, OCO, or S; a C.sub.7-C.sub.100 arylalkyl group; a carbamoyl group; a C.sub.5-C.sub.12 cycloalkyl group which can be substituted one to three times with a C.sub.1-C.sub.8 alkyl group and/or a C.sub.1-C.sub.8 alkoxy group; a C.sub.6-C.sub.24 aryl group; and pentafluorophenyl; and R.sup.3 is a C.sub.1-C.sub.50 alkyl group.

5. The semiconductor structure of claim 4, wherein the DPP polymer is selected from the group consisting of a polymer of formula (Ia): ##STR00033## a copolymer of formula (Ib): ##STR00034## a copolymer of formula (Ic): ##STR00035## and a copolymer of formula (Id): ##STR00036## wherein: x=0.995 to 0.005; y=0.005 to 0.995; with the proviso that x+y=1; r=0.985 to 0.005; s=0.005 to 0.985; t=0.005 to 0.985; u=0.005 to 0.985; with the proviso that r+s+t+u=1; n=4 to 1000; A is a group of formula: ##STR00037## a=1, 2, or 3; a=0, 1, 2, or 3; b=0, 1, 2, or 3; b=0, 1, 2, or 3; c=0, 1, 2, or 3; c=0, 1, 2, or 3; d=0, 1, 2, or 3; d=0, 1, 2, or 3; with the proviso that b is not 0 if a is 0; Ar.sup.1, Ar.sup.1, Ar.sup.2, Ar.sup.2, Ar.sup.3, Ar.sup.3, Ar.sup.4 and Ar.sup.4 are independently of each other heteroaromatic or aromatic rings, which optionally can be condensed and/or substituted; R.sup.112 and R.sup.113 are independently of each other H; C.sub.6-C.sub.18 aryl; C.sub.6-C.sub.18 aryl which is substituted by C.sub.1-C.sub.18 alkyl, or C.sub.1-C.sub.18 alkoxy; C.sub.1-C.sub.18 alkyl; or C.sub.1-C.sub.18 alkyl which is interrupted by O; B, D and E are independently of each other a group of formula: ##STR00038## or the formula (X), with the proviso that in case B, D and E are a group of formula (X), they are different from A; k=1; =0 or 1; r=0 or 1; z=0 or 1; Ar.sup.4, Ar.sup.5, Ar.sup.6 and Ar.sup.7 are independently of each other a group of formula: ##STR00039## one of X.sup.5 and X.sup.6 is N and the other is CR.sup.14; R.sup.14, R.sup.14, R.sup.17 and R.sup.17 are independently of each other H, or a C.sub.1-C.sub.25 alkyl group, which may optionally be interrupted by one or more oxygen atoms.

6. The semiconductor structure of claim 5, wherein the DPP polymer is a polymer according to formula (Ib-1), (Ib-9), or (Ib-10): ##STR00040## R.sup.1 and R.sup.2 are independently from each other a C.sub.8-C.sub.36 alkyl group; and n=4 to 1000.

7. The semiconductor structure of claim 4, wherein: Ar.sup.1, Ar.sup.1, Ar.sup.2, Ar.sup.2, Ar.sup.3, Ar.sup.3, Ar.sup.4 and Ar.sup.4 are independently of each other: ##STR00041## one of X.sup.3 and X.sup.4 is N and the other is CR.sup.99; R.sup.99, R.sup.104, R.sup.104, R.sup.123 and R.sup.123 are independently of each other hydrogen, halogen, especially F, or a C.sub.1-C.sub.25 alkyl group, especially a C.sub.4-C.sub.25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C.sub.7-C.sub.25 arylalkyl, or a C.sub.1-C.sub.25 alkoxy group; R.sup.105, R.sup.105, R.sup.106 and R.sup.106 are independently of each other hydrogen, halogen, C.sub.1-C.sub.25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; C.sub.7-C.sub.25 arylalkyl, or C.sub.1-C.sub.18 alkoxy; R.sup.107 is C.sub.7-C.sub.25 arylalkyl, C.sub.6-C.sub.18 aryl; C.sub.6-C.sub.18 aryl which is substituted by C.sub.1-C.sub.18 alkyl, C.sub.1-C.sub.18 perfluoroalkyl, or C.sub.1-C.sub.18 alkoxy; C.sub.1-C.sub.18 alkyl; C.sub.1-C.sub.18 alkyl which is interrupted by O, or S; or COOR.sup.124, R.sup.124 is C.sub.1-C.sub.25 alkyl group, especially a C.sub.4-C.sub.25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C.sub.7-C.sub.25 arylalkyl; R.sup.108 and R.sup.109 are independently of each other H, C.sub.1-C.sub.25 alkyl, C.sub.1-C.sub.25 alkyl which is substituted by E and/or interrupted by D, C.sub.7-C.sub.25 arylalkyl, C.sub.6-C.sub.24 aryl, C.sub.6-C.sub.24 aryl which is substituted by G, C.sub.2-C.sub.20 heteroaryl, C.sub.2-C.sub.20 heteroaryl which is substituted by G, C.sub.2-C.sub.18 alkenyl, C.sub.2-C.sub.18 alkynyl, C.sub.1-C.sub.18 alkoxy, C.sub.1-C.sub.18 alkoxy which is substituted by E and/or interrupted by D, or C.sub.7-C.sub.25 aralkyl; or R.sup.108 and R.sup.109 together form a group of formula CR.sup.110R.sup.111, wherein R.sup.110 and R.sup.111 are independently of each other H, C.sub.1-C.sub.18 alkyl, C.sub.1-C.sub.18 alkyl which is substituted by E and/or interrupted by D, C.sub.6-C.sub.24 aryl, C.sub.6-C.sub.24 aryl which is substituted by G, or C.sub.2-C.sub.20 heteroaryl, or C.sub.2-C.sub.20 heteroaryl which is substituted by G; or R.sup.108 and R.sup.109 together form a five or six-membered ring, which optionally can be substituted by C.sub.1-C.sub.18 alkyl, C.sub.1-C.sub.18alkyl which is substituted by E and/or interrupted by D, C.sub.6-C.sub.24 aryl, C.sub.6-C.sub.24 aryl which is substituted by G, C.sub.2-C.sub.20 heteroaryl, C.sub.2-C.sub.20 heteroaryl which is substituted by G, C.sub.2-C.sub.18 alkenyl, C.sub.2-C.sub.18 alkynyl, C.sub.1-C.sub.18 alkoxy, C.sub.1-C.sub.18 alkoxy which is substituted by E and/or interrupted by D, or C.sub.7-C.sub.25 aralkyl; D is CO, COO, S, O, or NR.sup.112; E is C.sub.1-C.sub.8 thioalkoxy, C.sub.1-C.sub.8 alkoxy, CN, NR.sup.112R.sup.113, CONR.sup.112R.sup.113, or halogen; and G is E, or C.sub.1-C.sub.18 alkyl.

8. The semiconductor material of claim 1, wherein the organic semiconductor material has a polydispersity in the range of from 1.01 to 10.

9. The semiconductor structure of claim 1, wherein the openings have an inner width of more than 200 nm.

10. The semiconductor structure of claim 1, wherein the conductive material comprises a metal, an alloy, or a conductive polymer.

11. The semiconductor structure of claim 1, further comprising at least two electrodes at end faces of the semiconductor regions, and wherein the electrodes as well as the conductor region each comprise a contact region or are provided with a conductor adapted for external contact.

12. The semiconductor structure of claim 1, wherein: the semiconductor regions are in direct contact with each other through the openings of the conductor region; and the semiconductor regions are separated by the conductor region by sections of the conductor region, which sections are lateral to the openings.

13. The semiconductor structure of claim 1, comprising a conductor region partly separating two semiconductor regions, wherein: the conductor region and the two semiconductor regions provide a vertical transistor structure; and the conductor region provides a gate adapted for conductivity control between the semiconductor regions.

14. A method for producing the semiconductor structure according to claim 1, the method comprising: (a) providing at least two semiconductor regions comprising at least one organic semiconductor material; (b) providing at least one conductor region between the at least two semiconductor regions; (c) providing openings in the at least one conductor region extending through the entire conductor region; and (d) partly contacting the at least two semiconductor regions through the openings of the at least one conductor region, wherein: the organic semiconductor material of (a) has a HOMO (highest occupied molecular orbital) energy level E.sub.H defined by:
5.0 eV|E.sub.H|5.8 eV; and the at least one conductor region provided in (b) comprises a conductive material having a work function E.sub.C defined by:
|E.sub.H|1.5 eV|E.sub.C||E.sub.H|0.4 eV.

15. The method of claim 14, comprising: (b) providing the at least one conductor region as a continuous layer of the conductive material; and (c) embossing, mechanically cutting or laser cutting the openings with an inner width of the openings of more than 200 nm through the continuous layer.

16. A semiconductor structure, comprising at least one conductor region and at least two semiconductor regions which are partly separated by the at least one conductor region, wherein: the at least one conductor region comprises openings extending between the semiconductor regions; the semiconductor regions comprise at least one organic semiconductor material which is a diketopyrrolopyrrole (DPP) polymer; the conductor region comprises a metal selected from the group consisting of Al, Cr, Cu, Fe, In, Sb, Si, Sn, and Zn; and contacts between each of the at least one conductor region and each of the at least one semiconductor region are Schottky contacts.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows an inventive semiconductor structure in form of a schematic drawing.

DETAILED DESCRIPTION OF THE FIGURE

(2) In FIG. 1, an embodiment of the inventive semiconductor structure is shown in a sectional side view. The depiction is not drawn to scale, in particular with respect to the widths of the structure elements. The semiconductor structure comprises an electrode 10 with an electrical connection 12. Electrode 10 is made of conducting material. Further, the structure comprises a conductor region 20, which is provided with openings 22. The openings 22 extend perpendicular to the direction along which the conductor region 20 extends. Between the first electrode 10 and the conductor region 20, a first semiconductor region 30 is provided, which extends from the first electrode 10 to the conductor region 20. On the side of the conductor region 20, opposed to the semiconductor region 30, a second semiconductor region 40 is located. Further, a second electrode 50 is provided, together with an electrical connection 52. The second electrode 50 is arranged on the side of the second semiconductor region 40, which is opposed to the conductor region 20 as well as to the first semiconductor region 30. Therefore, the first electrode 10 as well as the second electrode 50 are located at opposed end faces of the semiconductor structure. In particular, the electrodes 10 and 50 are located at end faces of the semiconductor regions 30 and 40, which are opposed to the conductor region 20.

(3) The structure shown in FIG. 1 is a layered structure such that the electrodes 10 and 50, the conductor region 20 as well as the first and the second semiconductor regions 30 and 40 are provided as layers with a constant thickness. The openings 22 are filled with semiconductor material such that the first semiconductor region 30 and the second semiconductor region 40 are physically connected with each other by the semiconductor material within the openings 22. The conductor region 20 can be provided with an electrical connector in order to impose a certain voltage onto the conductor region 20.

(4) For example, if a certain voltage is applied between the second electrode 50 and the conductor region 20, the semiconductor region 40 in-between, i.e. the second semiconductor region, is modified as regards its electrical properties. In particular, the voltage between the conductor region 20 and the second electrode 50 imposes an electrical field within the second semiconductor region 40 which increases the bulk concentration of free charge carriers or their equivalents within the second semiconductor region 40. Thus, if an additional voltage is applied at the electrodes 50 and 10, a current is generated based on the free charge carriers within the semiconductor regions 30, 40, the bulk concentration of which is controlled via the voltage applied at the conductor region 20. In this way, a gain can be produced and the voltage at the conductor region 20 controls a current between the electrical connections 12 and 52 of the first and second electrode 10, 50. In particular, by applying voltage difference between the electrodes 10 and 50, the charge carrier movement is controlled by applying a voltage to the conductor region 20. This voltage varies a depletion range located at the conductor region 20 and the semiconductor region 30. In addition, a depletion range located at the conductor region 20 and the semiconductor region 40 can be varied. In this way, a channel for charge carriers is opened, which travel from the semiconductor region 30 to the semiconductor region 40 through the openings 22. If not voltage is applied to conductor region 20, the depletion range covers the area of 22, and charges do not travel through openings resulting in a transport current between the semiconductor regions 30 and 40 of zero.

(5) According to an exemplifying embodiment, the electrodes 10 and 50 can be formed of a layer of evaporated gold and the first and the second semiconductor region 30, 40 can be provided by layers of DPP, which are preferably produced by casting the organic semiconductor material dissolved in a solvent. Of course, after dissolved organic semiconductor material is applied, the solvent has to be removed before another structural element is applied to the respective semiconductor region 30, 40. The conductor region 20 can be formed of a layer of aluminium, preferably with a thickness of less than 100 nm or less than 50 nm. The openings 22 in the conductor region 20 are provided by nanoimprinting lithography into a layer of aluminium, which provides the conductor region 20 and which is formed by evaporation of aluminium onto one of the semiconductor regions 30 or 40. The openings 22 have an inner width of e.g. 500 nm.

REFERENCE SIGNS

(6) 10 first electrode 12 electrical connection 20 conductor region 22 openings 30 first semiconductor region 40 second semiconductor region 50 second electrode 52 electrical connection

CITED DOCUMENTS

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