CONTROLLED ORGANIC SEMICONDUCTOR ELEMENT AND METHOD FOR MAKING THE SAME

Abstract

Organic bipolar transistor (100), comprising a crystalline first organic semiconductor layer (108) on or above a substrate (102), wherein the crystalline first organic semiconductor layer (108) has a first conduction type; and a crystalline second organic semiconductor layer (112) on or above the crystalline first organic semiconductor layer (108), wherein the crystalline second organic semiconductor layer (112) has a second conduction type, wherein the first conduction type differs from the second conduction type, wherein the crystalline first organic semiconductor layer (108) has a first dopant and the crystalline second organic semiconductor layer (112) has a second dopant which differs from the first dopant; wherein the crystalline first organic semiconductor layer (108) exhibits a first crystallinity and the crystalline second organic semiconductor layer (112) exhibits a second crystallinity, where the second crystallinity is less than or equal to the first crystallinity; a third organic semiconductor layer (110) arranged between the crystalline first organic semiconductor layer (108) and the crystalline second organic semiconductor layer (112), wherein the third organic semiconductor layer (110) is undoped, wherein the third organic semiconductor layer (110) has a third crystallinity that is less than or equal to the first crystallinity of the crystalline first organic semiconductor layer (108); and a fourth organic semiconductor layer (116) arranged on or above the crystalline second organic semiconductor layer (112), wherein the fourth organic semiconductor layer (116) has the same conduction type as the crystalline first organic semiconductor layer (108), wherein the fourth organic semiconductor layer (116) has a fourth crystallinity that is less than or equal to the second crystallinity of the crystalline second organic semiconductor layer (112).

Description

[0001] Transistors are used in a wide variety of electronic applications, such as signal amplification and logic circuitry. These applications can be implemented using bipolar transistors or field-effect transistors. Field-effect transistors are generally preferred for microelectronics in integrated circuits due to their simpler miniaturization. Bipolar transistors can outperform field-effect transistors in areas such as high-frequency power handling, frequency bandwidth, maximum current density, impedance matching, and more.

[0002] US 2005 / 0275056A1 describes a bipolar transistor whose collector comprises a small-molecule organic material. The transistor includes a base, which comprises a doped small-molecule organic material and forms a connection with the collector, and an emitter, which comprises a small-molecule organic material and forms a connection with the base. Electrodes are connected to the collector, the base, and the emitter.

[0003] Liu, Jinyu, et al., “Vertical organic field-effect transistors.” (Advanced Functional Materials 29.17 (2019): 1808453) provides an overview of organic field-effect transistors (OFETs), in particular vertical organic field-effect transistors (VOFETs), which feature vertically stacked source / drain electrodes. The article outlines the development of vertical organic field-effect transistors, with a focus on optimizing the device structure.

[0004] Liu, Shiyi, et al., “Vertical organic tunnel field-effect transistors.” (ACS Applied Electronic Materials 1.8 (2019): 1506-1516), describe a vertical organic tunnel field-effect transistor. Based on heterogeneously doped drain and source contacts, charge carriers are injected through Zener tunnels from an n-doped source electrode into the channel and transported to a p-doped drain electrode. The Zener junction between the source and drain of the vertical organic tunnel field-effect transistors suppresses short-channel effects and improves the saturation of vertical OFETs.

[0005] Kaschura, Felix, et al. “Controlling morphology: A vertical organic transistor with a self-structured permeable base using the bottom electrode as seed layer.” (Applied Physics Letters 107.3 (2015)) describes a permeable base transistor. By adding a morphology-modulating gold layer below the organic semiconductor, the interface with the base electrode is influenced, leading to the formation of a self-structured permeable base.

[0006] Watanabe, Hiroki, Ryo Nouchi, and Katsumi Tanigaki. “Effect of flexibility on the formation of conducting layers at organic single crystal heterointerfaces.” (Japanese Journal of Applied Physics 49.12R (2010): 120201) investigates the electrical conductivity of organic single-crystal heterointerfaces. Electron transfer occurs at the interface between rubrene and 7,7,8,8-tetracyanoquinodimethane (TCNQ) from the highest occupied molecular orbital of rubrene to the lowest unoccupied molecular orbital of TCNQ, thus making the interface conductive. A conducting layer forms at a rubrene-on-TCNQ heterointerface, but not at a TCNQ-on-rubren heterointerface prepared on a rigid SiO₂ / Si substrate.

[0007] A bipolar transistor based on organic semiconductor materials has not yet been technically feasible. This is partly due to the fundamental properties of most known organic semiconductor materials, since—unlike inorganic solids—most organic materials are structurally amorphous or can only be technically processed (e.g., deposited) in a structurally amorphous form. Amorphous materials generally exhibit low long-range order, which, within an organic device, for example, can lead to inefficient charge carrier transport over long distances and / or a large number of impurities and recombination sites. This, in turn, can result in extremely short diffusion lengths, for example, in the range of a few nanometers. For the function of a bipolar transistor, however, a long diffusion length in the material forming the respective pn-np junction (or...) is crucial.which forms the exclusion zone), will be crucial.

[0008] In general, the diffusion length of charge carriers until recombination correlates with the degree of order in the system. Highly ordered organic semiconductor materials (organic single crystals) are typically grown via sublimation in reactors. Although the quality (order) of the organic crystals can be high, their macroscopic size, shape, and orientation are random. This means that high-quality organic semiconductor crystals can only be grown using complex and slow sublimation methods. Furthermore, such conventional organic crystals cannot be grown directly and flat on substrates but must be painstakingly transferred manually. The thickness of the organic crystal can range, for example, from several hundred nm to a few micrometers. It follows that a bipolar transistor based on these organic crystals would need a base length of at least one crystal thickness.The diffusion length would therefore have to be at least as long.

[0009] A bipolar transistor requires a pn junction formed by two regions of differing conductivity. These different conductivities are achieved through varying doping concentrations. In organic crystals, these regions of differing doping concentrations can only be created laterally or by stacking individual crystals. Doping crystals grown in a reactor is currently not technically feasible, as the sublimation temperature of the matrix and the dopant would have to match. Loose single crystals can only be doped through their surface, which can result in uneven and / or incomplete doping. The minimum region dimension is then determined by the structuring method or the thickness of the crystals, which is on the order of several hundred nanometers or several micrometers.The advantage of long diffusion lengths in the organic crystal is then negated due to the thick layers.

[0010] The invention is therefore based on the objective of providing an organic bipolar transistor that reduces or eliminates one or more of the aforementioned problems, and a method for manufacturing the same. This objective is achieved by an organic bipolar transistor according to claims 1 and 11, and by a method according to claims 13 and 20.

[0011] In one aspect, a controlled organic semiconductor device is provided. The controlled organic semiconductor device comprises: a crystalline first organic semiconductor layer on or above a substrate, wherein the crystalline first organic semiconductor layer has a first conduction type; and a crystalline second organic semiconductor layer on or above the first organic semiconductor layer, wherein the crystalline second organic semiconductor layer has a second conduction type, the first conduction type being different from the second conduction type.

[0012] Visually, the crystalline structure or crystallinity, for example the crystal structure or crystal system (lattice type), of the first organic semiconductor layer continues into the second organic semiconductor layer.

[0013] This enabled an organic semiconductor junction with a larger barrier zone between the crystalline first and second organic semiconductor layers compared to the case where the second organic semiconductor layer is an amorphous organic layer. This allows for the realization of a controlled organic semiconductor device with improved regulation. The barrier zone can be increased and / or adjusted in various embodiments by adding a further (third), crystalline, intrinsic organic semiconductor layer between the first and second organic semiconductor layers. In this case, the crystallinity of the first organic semiconductor layer can propagate through the third organic semiconductor layer into the second organic semiconductor layer.

[0014] Furthermore, the smaller parasitic capacitances enable a controlled organic semiconductor device with a higher switching frequency. This allows for higher power at high frequencies, a wider frequency bandwidth, a higher maximum current density, and advantages in impedance matching.

[0015] Furthermore, compared to a controlled inorganic semiconductor device, the controlled organic semiconductor device exhibits greater flexibility, higher transparency, low weight, low material consumption, and greater adaptability, etc.

[0016] The controlled organic semiconductor device has a control terminal for controlling or regulating a current flow. Within the scope of this description and in various embodiments, the control terminal can also be referred to as a third electrode, control electrode, control contact, gate electrode, or base electrode. The control terminal can be at least partially embedded in one of the organic semiconductor layers or surrounded by one or more organic semiconductor layers. The control terminal can be designed such that control over the control current is ensured and parasitic leakage currents are minimized.

[0017] The terms "controlled" and "controllable" are used synonymously in this description. In particular, a "controlled component" also includes the component in the switched-off or unenergized state (controllable component). A controlled organic semiconductor component is, for example, a transistor, such as an organic bipolar transistor or an organic field-effect transistor; a controlled diode, such as an organic thyristor; or a controlled diode circuit, such as an organic triac.

[0018] The first organic semiconductor layer can be hole-conducting (also known as p-type or p-type), and the second organic semiconductor layer can be electron-conducting (also known as n-type or n-type). Alternatively, the first organic semiconductor layer can be electron-conducting, and the second organic semiconductor layer can be hole-conducting. In a hole-conducting layer, the majority charge carriers are free holes (electron vacancies), which have a higher mobility than electrons through the organic semiconductor layer. In an electron-conducting layer, the majority charge carriers are free electrons, which have a higher mobility than holes (electron vacancies) through the organic semiconductor layer. Therefore, the first and second conductivity types, as described here, can refer to qualitatively different conductivities.Alternatively or additionally, the first and second conductor types can refer to different doping concentrations, for example n, p, n-, n--, p+, p++. Within the scope of this description, a semiconductor layer can have a doping concentration or dopant in a matrix or host if the semiconductor layer is not described as "undoped" or "intrinsic".

[0019] In this description, the terms "conductive" and "conductive" are used synonymously for semiconductor layers, unless the terms are explicitly used differently.

[0020] In various embodiments, the controlled organic semiconductor device can have a pin or nip structure instead of a pn or np structure, i.e., an intrinsic third organic semiconductor layer between the first and second organic semiconductor layers. This allows for a thicker depletion zone, for example, to compensate for a potentially small depletion zone thickness in the organic semiconductor device or in the pn junction. Depending on the application, different combinations of p-type, n-type, and intrinsically conductive layers can be implemented in various embodiments, for example, npn, nipn, nipin, pnp, pinp, pinip, or combinations thereof. The semiconductor layers or combinations can be stacked on top of each other and / or arranged side by side on or above the (common) substrate.Combinations can be arranged, for example, between a (common) first electrode and a (common) second electrode, such as an emitter and collector electrode or a source and drain electrode, on or above the substrate.

[0021] In various embodiments, one or more electron or hole blocking layers (also referred to as blocking layers or blocking layers) to minimize parasitic currents; one or more electron or hole injection layers to improve charge carrier injection; and one or more electron or hole transport layers to improve charge carrier transport may also be provided in the layer stack of the controlled organic semiconductor device.

[0022] The type of controlled semiconductor device can be configured by adjusting the shape or geometry of the control electrode, for example by adjusting the ratio of active to passive areas. This allows, for instance, the realization of an organic bipolar transistor.

[0023] In another aspect, a method for forming a controlled organic semiconductor device is provided, comprising: forming a crystalline first organic semiconductor layer on or over a substrate, wherein the first organic semiconductor layer has a first conduction type; and forming a crystalline second organic semiconductor layer on or over the first organic semiconductor layer, wherein the second organic semiconductor layer has a second conduction type, the first conduction type being different from the second conduction type.

[0024] The first organic semiconductor layer can be formed on the substrate by evaporation or sublimation, for example by growth, and can be processed or structured using conventional thin-film technology. The length of the control electrode of the controlled organic semiconductor device can be freely adjustable.

[0025] The first and second organic semiconductor layers are formed in such a way, or based on a process, that bulk or volume doping of holes (p) and electrons (n) into a matrix material or a host material is possible.

[0026] To illustrate, the targeted application of a new growth method for organic semiconductor crystals (optionally combined with chemical doping via co-evaporation) can enable organic semiconductor layers with significantly longer diffusion lengths than previously possible in organic semiconductors.

[0027] Examples of implementation are shown in the figures and are explained in more detail below.

[0028] They show Fig. 1A-C Schematic cross-sectional views of controlled organic semiconductor devices according to various embodiments; Fig. 2 a schematic top view of a controlled organic semiconductor device according to various embodiments; Fig. 3 a schematic top view of a controlled organic semiconductor device according to various embodiments; and Fig. 4 a flowchart of a process for manufacturing a controlled organic semiconductor device according to various embodiments.

[0029] The following detailed description refers to the accompanying drawings, which form part of the description and illustrate specific embodiments in which the invention can be implemented. It is understood that other embodiments may be used and structural or logical modifications may be made without deviating from the scope of protection of the present invention. It is understood that the features of the various exemplary embodiments described herein may be combined with one another, unless specifically stated otherwise. The following description is therefore not to be interpreted restrictively, and the scope of protection of the present invention is defined by the attached claims.

[0030] Fig. Figures 1A-C illustrate embodiments of a controlled organic semiconductor device 100 according to different embodiments.

[0031] In Fig. Figures 1A-C illustrate embodiments of a controlled organic semiconductor device 100 with several organic semiconductor layers 108, 110, 112, 114, 116, which may have different conductor types.

[0032] The controlled organic semiconductor device 100 can, in various embodiments, have a first electrode 130, a second electrode 118, and a third electrode 122. The third electrode 122 is configured as a control electrode to regulate the current flow between the first electrode 130 and the second electrode 118. The third electrode 122 can be embedded in one of the semiconductor layers 108, 110, 112, 114, or 116, as shown in Figure 1. Fig. Figure 1A illustrates this. Alternatively or additionally, the third electrode 122 can be at least partially surrounded by one or more of the semiconductor layers 108, 110, 112, 114, 116, as shown in Fig. 1B and Fig. 1C is illustrated. For example, at least a section of the third electrode 122 is embedded in the second organic semiconductor layer 112, as shown in Fig. 1A is illustrated, or at least partially surrounded by it, as in Fig. 1B and Fig. Figure 1C illustrates this. The third electrode 122 can have a structuring, wherein the structuring has one or more finger shapes and / or a meander shape, as shown in Fig. 2 and Fig. Figure 3 illustrates this.

[0033] The multiple organic semiconductor layers 108, 110, 112, 114, 116 are arranged on or above a substrate 102 / 130. The substrate 102 can be configured as the first electrode 130 or may have the first electrode 130. For example, in addition to the first electrode 130, the substrate 102 may have further layers, such as a buffer layer 104 and / or a crystal growth layer 106, as shown in Fig. 1C is illustrated. At least some of the organic semiconductor layers 108, 110, 112, 114, 116 are crystalline.

[0034] The crystallinity, for example the crystal structure or the lattice type, or the formation of a crystal structure, can extend from the first crystalline organic semiconductor layer 108 at least to the second crystalline organic semiconductor layer 112. This can enable an increase in the depletion region in the semiconductor device 100 and improve the control of the controlled organic semiconductor device compared to a device with an amorphous semiconductor layer. Alternatively or additionally, this can increase the switching frequency. Without crystalline organic semiconductors or with amorphous organic semiconductors, the required (long) diffusion lengths of the charge carriers at the pn junction could not be achieved. Without doping, the pn junction or the energy levels may not be adjustable.Doped, crystalline organic semiconductor layers enable the realization of a controllable semiconductor device. An organic semiconductor layer with high crystallinity, for example, greater than approximately 80% (using any measurement method), or greater than 90%, can imply high charge carrier mobility. This allows for a steeper rise time during turn-on. Consequently, the dead time between turn-off and turn-on can be reduced, thus enabling an increase in the switching frequency.

[0035] The second organic semiconductor layer 112 can have the same crystal structure, for example a cubic crystal structure (bcc), as the first organic semiconductor layer 108, for example in the case that the first and second semiconductor layers 108, 112 are formed from the same or a similar matrix or host material.

[0036] Alternatively, the second organic semiconductor layer can have a material-specific crystal structure different from that of the first organic semiconductor layer 108, but compatible with it. This is possible, for example, if the first and second semiconductor layers 108, 112 are made of different matrix or host materials. For instance, the second semiconductor layer 112 can have an hcp or fcp crystal structure with a lattice constant that is the same as or similar to (compatible with) a lattice constant of the crystal structure (e.g., bcc) of the first organic semiconductor layer 108. The first organic semiconductor layer 108 can thus be visualized as a seed layer or crystal growth layer for the second organic semiconductor layer 112.

[0037] In various embodiments, the crystallinity of the first organic semiconductor layer can be enhanced by a (or more) third semiconductor layer 110, which is arranged between the first and second organic semiconductor layers 108, 112 (see Fig. 1B and Fig. 1C), extend into the second organic semiconductor layer 112.

[0038] In various embodiments, the crystallinity of the first organic semiconductor layer can extend into one or more organic semiconductor layers on or above the second semiconductor layer 112, for example into a fourth organic semiconductor layer 116 and / or a fifth semiconductor layer 114.

[0039] In various embodiments, the controlled organic semiconductor device 100 is configured as an organic transistor 100, for example as an organic bipolar transistor or an organic field-effect transistor, as in Fig. 1A to Fig. Figure 1C illustrates this. The organic transistor 100 can have a pnp or an npn layer stack of organic (crystalline) semiconductor layers 108, 112, 116, as shown in Fig. Figure 1A illustrates this. Alternatively, the organic transistor 100 can have a pinip or nipin layer stack of organic (crystalline) semiconductor layers 108, 110, 112, 114, 116, as shown in Fig. 1B and Fig. Figure 1C is illustrated. Alternatively (not illustrated), the organic transistor 100 can have a different layer sequence, for example nipn, npin, npni, ipnp, pinp, pipn, pnpi, ipnp.

[0040] In various embodiments, a non-conductive layer and / or an insulating layer can also be provided in the layer stack, for example, adjacent to the control electrode (third electrode). This allows, for example, the realization of a field-effect transistor (FET) or an insulated-gate bipolar transistor (IGBT). The insulating layer or the non-conductive layer can be an organic layer, for example, a crystalline organic layer. The non-conductive organic layer can have a band gap, for example, by means of no or low doping and / or appropriate crystal orientation with respect to directly adjacent semiconductor layers, which leads to a non-conductive state during operation of the semiconductor device.The non-conducting layer can have a different crystal orientation, for example set by means of the evaporation parameters, than the directly adjacent p-, n-, or i-conducting organic layer(s). An organic semiconductor layer formed on the insulating or non-conducting semiconductor layer can be crystalline, for example, single-crystal or polycrystalline, or amorphous.

[0041] Alternatively (not illustrated), the controlled organic semiconductor device 100 can be configured as a controlled diode, for example an organic thyristor; or a controlled diode circuit, for example an organic triac, with a pn, np, nip or pin stack of organic (crystalline) semiconductor layers 108, 110, 112 or combinations thereof, for example ipn, inp, nipi, pini, ipni, inpi, etc.

[0042] In various embodiments, application-specific combinations of p-, i- and n-conducting crystalline organic semiconductor layers can be provided between the first electrode 130 and the second electrode 118 on or above the substrate 102.

[0043] In various embodiments, the combinations of semiconductor layers can be arranged side by side and / or stacked on top of each other on or above the substrate 102. Several controlled organic semiconductor devices 100 can also be arranged side by side or stacked on top of each other on a common substrate 102. In various embodiments, several controlled organic semiconductor devices 100 on or above a common substrate 102 can have at least one common electrode 130, 118.

[0044] For example, the controlled organic semiconductor device 100 has a crystalline first organic semiconductor layer 108 on or above a substrate 102 and a crystalline second organic semiconductor layer 112 on or above the first organic semiconductor layer 108. The crystalline first organic semiconductor layer 108 has a first conduction type, for example p-type, and the crystalline second organic semiconductor layer 112 has a second conduction type, for example n-type. The first conduction type can differ from the second conduction type. This allows a pn junction with a depletion region between the first and second organic semiconductor layers 108, 112 to be formed.

[0045] The first organic semiconductor layer 108 can be hole-conducting and / or p-doped and the second organic semiconductor layer can be electron-conducting and / or n-doped, or vice versa.

[0046] The first organic semiconductor layer 108 can exhibit a first crystallinity, and the second organic semiconductor layer 112 can exhibit a second crystallinity. The second crystallinity can be less than or equal to the first crystallinity. For the purposes of this description, the crystallinity of a layer is the relative proportion of the crystalline volume or mass fraction of the layer to the total layer. Crystallinity can be determined by density measurement, differential scanning calorimetry (DSC), X-ray diffraction, infrared spectroscopy, and / or nuclear magnetic resonance spectroscopy. Due to the manufacturing process, the crystal order or crystallinity of the first organic semiconductor layer 108 extends into the second organic semiconductor layer 112.Therefore, the second organic semiconductor layer 112 should have the same crystallinity as the first organic semiconductor layer or a lower crystallinity, for example in the case that the crystallinity is only taken from the first organic semiconductor layer 108 in the vicinity of the interface to the first organic semiconductor layer 108.

[0047] The first organic semiconductor layer 108 may contain or be formed from a first type of low molecular weight conjugated molecules.

[0048] Within the scope of this description, a low-molecular-weight, conjugated molecule can be one of the following: an oligoacene, for example anthracene, pentacene, or benzenethiolate – and a derivative thereof; a two-dimensionally condensed ring system, for example perylene, hexabenzocoronene, naphthalene, perylenetetracarboxylic dianhydride (PTCDA) – and a derivative thereof; a metal complex, for example phthalocyanines (Pc), aluminum tris(8-hydroxyquinoline) – and a derivative thereof; a dendritic molecule, for example a starburst molecule, for example 4,4',4"-tris(N,N-diphenylamino)triphenylamine (TDATA) – and a derivative thereof; or a heterocyclic oligomer, for example oligothiophenes, oligophenylenevinylene – and a derivative thereof.

[0049] The second organic semiconductor layer 112 can contain or be composed of a second type of low-molecular-weight conjugated molecule. The second type of conjugated molecule and the first type of conjugated molecule can be identical or derivatives of the same type of conjugated molecule.

[0050] The first organic semiconductor layer 108 can, for example, contain or be formed from rubrene or a derivative thereof. Alternatively or additionally, the second organic semiconductor layer 112 can contain or be formed from rubrene or a derivative thereof.

[0051] The first organic semiconductor layer 108 can have a first dopant and the second organic semiconductor layer 112 can have a second dopant that differs from the first dopant.

[0052] The second organic semiconductor layer 112 can be formed epitaxially on the first organic semiconductor layer 108, for example by means of a sublimation process. Alternatively or additionally, at least the second organic semiconductor layer 112 can be solvent-free.

[0053] A crystalline third organic semiconductor layer 110 can be arranged between the first organic semiconductor layer 108 and the second organic semiconductor layer 112. The third organic semiconductor layer 110 can be undoped or essentially undoped. In other words, the third organic semiconductor layer can be an intrinsically conductive layer. The third organic semiconductor layer 110 can be directly adjacent to the first organic semiconductor layer 108 and / or the second organic semiconductor layer 112. The third organic semiconductor layer 110 can have a third crystallinity that is less than or equal to the first crystallinity of the first organic semiconductor layer 108.

[0054] A fourth organic semiconductor layer 116 can be arranged on or above the second organic semiconductor layer 112. The fourth organic semiconductor layer 116 can optionally be crystalline. The fourth organic semiconductor layer 116 can have the same or substantially the same conductivity type as the first organic semiconductor layer 108. The fourth organic semiconductor layer 116 can have a fourth crystallinity that is less than or equal to the second crystallinity of the second organic semiconductor layer 112.

[0055] A fifth organic semiconductor layer 114 can be arranged between the second organic semiconductor layer 112 and the fourth organic semiconductor layer 116. The fifth organic semiconductor layer 114 can be undoped or essentially undoped. The fifth organic semiconductor layer 114 can be directly adjacent to the second organic semiconductor layer 112 and / or the fourth organic semiconductor layer 116.

[0056] The substrate 102 can have an organic crystal growth layer 106. The first organic semiconductor layer 108 can be arranged directly on the organic crystal growth layer 106.

[0057] Fig. Figure 1C illustrates, in a schematic cross-sectional view, an embodiment of a controlled organic semiconductor device according to various embodiments. The illustrated organic semiconductor device 100 can be a bipolar transistor and comprise thin layers of organic materials with high charge carrier mobility in all spatial directions.

[0058] In various embodiments, the substrate 102 comprises a stack of layers. The stack of layers can include the first electrode 130, the buffer layer 104, and the crystal growth layer 106. The stack of layers can be formed on a support (not shown). The support can, for example, be a glass substrate, a plastic film, or a metallic or semiconducting material, or be formed from such a material.

[0059] The first electrode 130 can, for example, be made of gold or have a gold content. This can enable effective hole injection. The first electrode 130 can, for example, have a thickness in the range of 10 nm to 500 nm, for example, in the range of 20 nm to 50 nm, for example, approximately 30 nm.

[0060] The buffer layer 104 can, for example, contain or be composed of 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC). The buffer layer 104 can enhance the growth of the crystal growth layer 106. The buffer layer 104 can, for example, have a thickness in the range of 1 nm to 20 nm, for example, in the range of 2 nm to 10 nm, for example, approximately 5 nm.

[0061] The crystal growth layer 106 can, for example, consist of or be formed from undoped or intrinsically conductive rubrene. The crystal growth layer 106 can, for example, have a thickness in the range of 5 nm to 100 nm, for example, in the range of 10 nm to 50 nm, for example, approximately 20 nm.

[0062] The crystalline first (p-type) organic semiconductor layer 108 can, for example, consist of or be composed of rubrene doped with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F6TCNNQ). The first organic semiconductor layer 108 can, for example, have a thickness in the range of 50 nm to 1000 nm, for example, in the range of 100 nm to 500 nm, for example, approximately 300 nm.

[0063] The crystalline third (intrinsic) organic semiconductor layer 110 can consist of or be composed of undoped or intrinsically conductive rubrene. The third organic semiconductor layer 110 can, for example, have a thickness in the range of 20 nm to 300 nm, for example in the range of 50 nm to 200 nm, for example approximately 100 nm.

[0064] The crystalline second (n-type) organic semiconductor layer 112 can, for example, comprise or be formed from rubrene doped with tetrakis(hexahydropyrimidinopyrimidine)ditungsten(II) (W2(hpp)4). The second organic semiconductor layer 112 can, for example, have a thickness in the range of 5 nm to 100 nm, for example, in the range of 10 nm to 50 nm, for example, approximately 20 nm.

[0065] The (crystalline) third (intrinsic) organic semiconductor layer 114 can consist of or be composed of undoped or intrinsically conductive rubrene. The fifth organic semiconductor layer 114 can, for example, have a thickness in the range of 20 nm to 300 nm, for example in the range of 50 nm to 200 nm, for example approximately 100 nm.

[0066] The (crystalline) fourth (p-type) organic semiconductor layer 116 can, for example, comprise or be composed of rubrene doped with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F6TCNNQ). The fourth organic semiconductor layer 116 can, for example, have a thickness in the range of 50 nm to 1000 nm, for example, in the range of 100 nm to 500 nm, for example, approximately 300 nm.

[0067] The second electrode 118 can, for example, be made of gold or have a thickness of approximately 30 nm. The second electrode 118 can, for example, have a thickness in the range of 10 nm to 500 nm, for example, in the range of 20 nm to 50 nm.

[0068] The third electrode 122 can be at least partially embedded in or surrounded by the second organic semiconductor layer 112 and / or the fifth organic semiconductor layer 114. The third electrode 122 can, for example, be made of aluminum. The thickness of the third electrode 122 can, for example, be in the range of 10 nm to 100 nm, for example, in the range of 25 nm to 75 nm, for example, approximately 50 nm.

[0069] Between the third electrode 122 and the second organic semiconductor layer 112 and / or the fifth organic semiconductor layer 114, one or more layers 120, 124, 128 can be provided to adjust the field distribution in the semiconductor device 100 and / or to eliminate or reduce leakage currents. For example, an n-C60 layer 124 with a thickness in the range of 5 nm to 20 nm, for example 10 nm, can be formed vertically between the third electrode 122 and the second organic semiconductor layer 112. The charge carrier injection can be improved, for example, by means of the n-C60 layer 124.Vertically between the third electrode 122 and the fifth organic semiconductor layer 114, an n-conducting layer 124 analogous to the second semiconductor layer 112 with a thickness in the range of 5 nm to 100 nm, for example 50 nm, may be formed; and an intrinsically conductive layer 126 analogous to the fifth semiconductor layer 114 with a thickness in the range of 5 nm to 100 nm, for example 50 nm, may be formed.

[0070] The individual layers 130, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124 can be formed epitaxially, for example by means of a sublimation process and / or co-evaporation, to form the doped semiconductor layers 108, 112, 116, layer by layer.

[0071] Fig. Figure 2 illustrates a schematic top view of a controlled organic semiconductor device 100 according to various embodiments, which may be configured according to a previously described embodiment.

[0072] The first electrode 130, for example as an emitter, has a width W E and the second electrode 118, as collector, has a width W C The first and second electrodes 130, 118 can each be designed (only as examples) as rectangles. The third electrode 122, as the base, can be designed (only as examples) with a finger structure (in Fig. 2 are 3 bars of width W B by far W L (illustrated) .

[0073] The first and second electrodes 130, 118 can overlap each other (overlap: L). E-C · W C ). The area of ​​the third electrode 122 that contributes to the controllable current is illustrated by Ic,s and is defined by the range of the field Wn of the third electrode 122 and the overlap (L E-C · W C ) of the first and second electrode 130, 118 realized.

[0074] Fig. Figure 2 illustrates the areas of the semiconductor device 100 that are active during operation or in which charge carriers (I) C,S ) between the first and second electrode 130, 118 are transported.

[0075] Fig. Figure 3 illustrates a schematic top view of a controlled organic semiconductor device according to various embodiments, which may be configured according to a previously described embodiment.

[0076] Analogous to the designations in Fig. 2 are in Fig. Figure 3 illustrates the areas of the semiconductor device 100 in which leakage currents or parasitic currents can occur.

[0077] The overlap areas of the first and third electrodes are illustrated. B-E ; first and second electrode I E-C as well as third and second electrode I B-C The overlap areas I B-E , I B-CThe third electrode contributes to the leakage current and can be blocked by means of blocking layers (see layers 120, 124, 126 in Fig. 1C) can be reduced. Alternatively, the width W can be reduced by suitable masking processes. B The finger structures are reduced, thus reducing leakage currents. The direct overlap I E-C The current between the first and second electrodes 130, 118 contributes to the leakage current, unless it is influenced by the electric field of the third electrode 122. This can be optimized by reducing the distance W. L the finger structures of the third electrode.

[0078] Fig. Figure 4 illustrates a flowchart of a process for manufacturing a controlled organic semiconductor device according to various embodiments.

[0079] Method 400 for forming a controlled organic semiconductor device 100 comprises: 410 forming a crystalline first organic semiconductor layer 108 on or over a substrate 102, wherein the first organic semiconductor layer 108 has a first conduction type; and 420 forming a crystalline second organic semiconductor layer 112 on or over the first organic semiconductor layer 108, wherein the second organic semiconductor layer 112 has a second conduction type, the first conduction type being different from the second conduction type.

[0080] The first organic semiconductor layer 108 can be formed with a first type of low-molecular-weight conjugated molecules. The second organic semiconductor layer 112 can be formed with a second type of low-molecular-weight conjugated molecules. The second type of conjugated molecules and the first type of conjugated molecules can be identical or derivatives of the same type of conjugated molecules.

[0081] The first organic semiconductor layer 108 may contain or be formed from rubrene or a derivative thereof. Alternatively or additionally, the second organic semiconductor layer 112 may contain or be formed from rubrene or a derivative thereof.

[0082] The second organic semiconductor layer 112 can be formed on the first organic semiconductor layer 108 using an epitaxy process. Alternatively or additionally, at least the second organic semiconductor layer 112 can be formed using a solvent-free process.

[0083] At least the second organic semiconductor layer 112 can have a second dopant which is introduced into the second organic semiconductor layer 112 by means of a co-evaporation process.

[0084] The substrate 102 can have an organic crystal growth layer 106, wherein the first organic semiconductor layer 108 is formed directly on the organic crystal growth layer 106.

[0085] The process is described below using the organic semiconductor rubren as an example.

[0086] A glass substrate can be prepared as a support. This process can include the mechanical and chemical cleaning of the glass substrate's surface as well as the manipulation of the surface energy (surface tension). For example, the surface of the glass substrate can be hydrophilized, for instance, using a piranha solution. A gold layer 120 can be formed on the surface of the glass substrate. Depending on the desired crystal phase, the surface can be further coated with a buffer layer 104, which has a specific glass transition temperature in the range of 110°C to 140°C. The buffer layer 104 can structurally decouple the subsequent host layer or crystal growth layer 106 from the glass substrate or the gold layer and can facilitate improved crystallization. Alternatively or additionally, the material of the buffer layer 104 can be selected to enable improved injection of charge carriers.

[0087] The crystal growth layer 106 can be formed on the buffer layer 104 or on the surface of the first electrode by thermal evaporation of rubrene in a vacuum with a thickness in the range of 20 nm to 100 nm. The resulting layer can be essentially amorphous after evaporation.

[0088] The crystal growth layer can optionally be doped with suitable chemical dopants by co-evaporation.

[0089] The amorphous crystal growth layer 106 can be transformed into a crystalline crystal growth layer 106 in a thermal annealing process. The transformation or crystallization can be carried out, for example, under a protective gas atmosphere for a predetermined time, e.g., in a range of 30 s to 15 min, at a predetermined temperature, e.g., in a range of 120°C to 180°C, e.g., 60 s at 160°C. This can lead to orthorhombic base-centered rubrene crystals.

[0090] The crystal growth layer 106 can subsequently act as a host crystal for the epitaxial growth of the further semiconductor layers, in particular the first and second organic semiconductor layers. For example, the material (see Fig. 1C) The optional additional organic semiconductor layers 108, 110, 112, 114, 116 are formed on the crystal growth layer 105 by thermal evaporation or co-evaporation. The thickness of the individual layers can be selected with nanometer precision. Optionally, after evaporation, the optional additional organic semiconductor layers 108, 110, 112, 114, 116 can be converted into a predetermined crystal structure or crystallized by one of the thermal annealing processes.

[0091] For example, the first organic semiconductor layer 108 made of rubren with 5wt% of the p-doping agent F6TCNNQ is epitaxially formed on the first organic semiconductor layer 108 by thermal co-evaporation and a thickness of 300 nm.

[0092] The third organic semiconductor layer 110 is epitaxially formed from rubren by thermal evaporation and has a thickness of 100 nm.

[0093] The second organic semiconductor layer 112 is epitaxially formed on the third organic semiconductor layer 110 by thermal co-evaporation of rubrene with 1 wt% to 5 wt% W2(hpp)4 with a thickness of 10 nm to 50 nm.

[0094] The third electrode 122 can be structured onto the second semiconductor layer 110, for example by means of a mask process, and optional blocking layers 120, 124, 126 can be epitaxially formed to adjust the field distribution, for example by means of the mask for forming the third electrode.

[0095] For example, a blocking layer analogous to the second semiconductor layer can be epitaxially formed below the third electrode 122 by thermal co-evaporation of Rubren with 1 wt% to 5 wt% W₂(hpp)₄ and a thickness of 10 nm to 50 nm. This can reduce the current density of the direct (and therefore parasitic) diode from the first and third electrodes. Subsequently, the blocking layer 120, 10 nm thick, made of C₆O with 2 wt% of the dopant W₂(hpp)₄, can be epitaxially formed by co-evaporation. This can improve electron injection into the third electrode. Finally, the third electrode 122, made of aluminum with a thickness of 40 nm, can be epitaxially formed by thermal evaporation.

[0096] The blocking layer 124 can then be epitaxially formed by co-evaporation of rubrene with 0.5 wt% of the n-doping agent W2(hpp)4 to a thickness of 50 nm. This can serve as a blocking layer for the parasitic diode between the second and third electrodes.

[0097] The blocking layer 126 made of rubren (intrinsic / undoped) can then be epitaxially formed by thermal evaporation with a thickness of 100 nm. This can act as a blocking layer for the parasitic diode of the second and third electrodes.

[0098] On top of or above the second organic semiconductor layer 122, the fifth organic semiconductor layer 114 can be epitaxially formed by thermal evaporation (intrinsic / undoped) of rubrene with a thickness in the range of 100 nm to 200 nm. This layer can act as a blocking layer for the upper part of the pinip structure.

[0099] On the fifth organic semiconductor layer 114, the fourth organic semiconductor layer 116 can be epitaxially formed by thermal co-evaporation of rubrene doped with 5 wt% of the p-doper F6TCNNQ with a thickness of approximately 300 nm.

[0100] On the fourth organic semiconductor layer 116, the second electrode can be epitaxially formed by thermal evaporation of gold with a thickness of approximately 30 nm. This enables effective hole injection. The second electrode 118 can be structured using a shadow mask.

[0101] The third electrode 122 can be formed in or with a finger or meander structure. This makes it possible to reduce the direct overlap of the third electrode with the first and / or second electrode. At the same time, the edge region W can be n (see Fig. 2) the third electrode and the first or second electrode are enlarged. The width or extent W B The individual fingers of the third electrode can be designed to be as small as possible in various embodiments without compromising the integrity of the third electrode 122. The distance W L The individual fingers of the third electrode 122 can be adjusted to be as small as possible in various embodiments without the material from adjacent fingers completely covering the area between the fingers due to shadowing effects. The ideal distance can, for example, be twice the base range Wn, which can be predetermined by the lateral range of the field of the third electrode.

[0102] The first and second electrodes can be structured such that there is an overlap between the first and third electrodes, between the third and second electrodes, and between the first and second electrodes. For example, the first and second electrodes can be rectangles of different sizes. In various embodiments, the direct overlap between the first and third electrodes and / or between the second and third electrodes can be kept as small as possible. The overlap between the first and second electrodes can be limited to the area that can be controlled by the third electrode. Ideally, the first and second electrodes can be configured with a negative or inverted structure (comb or finger structure) relative to the structure of the third electrode (or with a slight overlap to accommodate alignment tolerances). This allows leakage currents to be minimized or reduced to a minimum.The structuring of the electrodes can be done using shadow mask evaporation or photolithography.

[0103] The thickness of the third electrode 122 can be freely adjusted. The sequence of the individual organic semiconductor layers 108, 110, 112, 114, 116 can also be freely selected according to the application. This allows for variation of the doping type and doping strength. Furthermore, the semiconductor layers 108, 110, 112, 114, 116 can be deposited in a structured manner, for example above or below the third electrode, in order to control the blocking or injection of charge carriers at predetermined locations.

[0104] These and Fig.Figure 1C illustrates the structure of the organic bipolar transistor 100, which is based on the pinip architecture, in contrast to the pnp structure used for inorganic devices. The additionally inserted intrinsic (i) organic semiconductor layers 110, 114 allow the weak current-blocking behavior of organic pn diodes to be compensated. Implementation as a nipin architecture (equivalent to npn) is also possible.

[0105] It is understood that functions, features, etc. described herein with reference to a device may also be implemented in the same or a similar way in a process and vice versa.

Claims

[1] Organic bipolar transistor (100), comprising a crystalline first organic semiconductor layer (108) on or above a substrate (102), wherein the crystalline first organic semiconductor layer (108) has a first conduction type; and a crystalline second organic semiconductor layer (112) on or above the crystalline first organic semiconductor layer (108), wherein the crystalline second organic semiconductor layer (112) has a second conduction type, wherein the first conduction type differs from the second conduction type, wherein the crystalline first organic semiconductor layer (108) has a first dopant and the crystalline second organic semiconductor layer (112) has a second dopant which differs from the first dopant; wherein the crystalline first organic semiconductor layer (108) exhibits a first crystallinity and the crystalline second organic semiconductor layer (112) exhibits a second crystallinity, where the second crystallinity is less than or equal to the first crystallinity; a third organic semiconductor layer (110) arranged between the crystalline first organic semiconductor layer (108) and the crystalline second organic semiconductor layer (112), wherein the third organic semiconductor layer (110) is undoped, wherein the third organic semiconductor layer (110) has a third crystallinity that is less than or equal to the first crystallinity of the crystalline first organic semiconductor layer (108); and a fourth organic semiconductor layer (116) arranged on or above the crystalline second organic semiconductor layer (112), wherein the fourth organic semiconductor layer (116) has the same conduction type as the crystalline first organic semiconductor layer (108), wherein the fourth organic semiconductor layer (116) has a fourth crystallinity that is less than or equal to the second crystallinity of the crystalline second organic semiconductor layer (112). [2] Organic bipolar transistor (100) according to claim 1, wherein the crystalline first organic semiconductor layer (108) comprises or is formed from a first type of low molecular weight conjugated molecules, and wherein the crystalline second organic semiconductor layer (112) has a second type of low molecular weight conjugated molecules or is formed from them, where the second type of conjugated molecules and the first type of conjugated molecules are the same or derivatives of the same type of conjugated molecules. [3] Organic bipolar transistor (100) according to claim 1 or 2, wherein the crystalline first organic semiconductor layer (108) comprises or is formed from rubrene or a derivative thereof; and / or wherein the crystalline second organic semiconductor layer (112) contains or is formed from rubrene or a derivative thereof. [4] Organic bipolar transistor (100) according to any one of claims 1 to 3, wherein the crystalline second organic semiconductor layer (112) is formed epitaxially on the crystalline first organic semiconductor layer (108), and / or wherein at least the crystalline second organic semiconductor layer (112) is solvent-free. [5] Organic bipolar transistor (100) according to any one of claims 1 to 4, wherein the third organic semiconductor layer (110) is directly adjacent to the first organic semiconductor layer (108) and / or the second organic semiconductor layer (112). [6] Organic bipolar transistor according to any one of claims 1 to 5, further comprising: a fifth organic semiconductor layer (114) arranged between the crystalline second organic semiconductor layer (112) and the fourth organic semiconductor layer (116), wherein the fifth organic semiconductor layer (114) is undoped, and wherein the fifth organic semiconductor layer (114) is directly adjacent to the crystalline second organic semiconductor layer (112) and / or the fourth organic semiconductor layer (116). [7] Organic bipolar transistor (100) according to any one of claims 1 to 6, wherein the substrate (102) has an organic crystal growth layer (106), wherein the crystalline first organic semiconductor layer (108) is arranged directly on the organic crystal growth layer (106). [8] Organic bipolar transistor (100) according to any one of claims 1 to 7, wherein the substrate (102) has a first electrode (130) of the organic bipolar transistor (100), and further comprising a second electrode (118) on or above the second organic semiconductor layer (112). [9] Organic bipolar transistor (100) according to any one of claims 1 to 8, further comprising: a third electrode (122), wherein at least a section of the third electrode (122) is embedded in the crystalline second organic semiconductor layer (112). [10] Organic bipolar transistor (100) according to claim 9, wherein the third electrode (122) has a structuring, wherein the structuring has one or more finger shape(s) and / or a meander shape. [11] Organic bipolar transistor (100) comprising a crystalline first organic semiconductor layer (108) on or over a substrate (102), wherein the crystalline first organic semiconductor layer (108) comprises a first conduction type; and a crystalline second organic semiconductor layer (112) on or above the crystalline first organic semiconductor layer (108), wherein the crystalline second organic semiconductor layer (112) has a second conduction type, wherein the first conduction type differs from the second conduction type, wherein the crystalline first organic semiconductor layer (108) has a first dopant and the crystalline second organic semiconductor layer (112) has a second dopant which differs from the first dopant; wherein the crystalline first organic semiconductor layer (108) exhibits a first crystallinity and the crystalline second organic semiconductor layer (112) exhibits a second crystallinity, where the second crystallinity is less than or equal to the first crystallinity; a fourth organic semiconductor layer (116) arranged on or above the crystalline second organic semiconductor layer (112), wherein the fourth organic semiconductor layer (116) has the same conduction type as the crystalline first organic semiconductor layer (108), wherein the fourth organic semiconductor layer (116) has a fourth crystallinity that is less than or equal to the second crystallinity of the crystalline second organic semiconductor layer (112); and a fifth organic semiconductor layer (114) arranged between the crystalline second organic semiconductor layer (112) and the fourth organic semiconductor layer (116), wherein the fifth organic semiconductor layer (114) is undoped. [12] Organic bipolar transistor (100) according to claim 11, wherein the fifth organic semiconductor layer (114) is directly adjacent to the crystalline second organic semiconductor layer (112) and / or the fourth organic semiconductor layer (116). [13] Method (400) for forming an organic bipolar transistor (100) comprising the method (400): Forming (410) a crystalline first organic semiconductor layer (108) on or over a substrate (102), wherein the crystalline first organic semiconductor layer (108) has a first conduction type; and Forming (420) a crystalline second organic semiconductor layer (112) on or above the crystalline first organic semiconductor layer (108), wherein the crystalline second organic semiconductor layer (112) has a second conduction type, wherein the first conduction type differs from the second conduction type, wherein the crystalline first organic semiconductor layer (108) has a first dopant and the crystalline second organic semiconductor layer (112) has a second dopant which differs from the first dopant; wherein the crystalline first organic semiconductor layer (108) exhibits a first crystallinity and the crystalline second organic semiconductor layer (112) exhibits a second crystallinity, where the second crystallinity is less than or equal to the first crystallinity; Formation of a third organic semiconductor layer (110) between the crystalline first organic semiconductor layer (108) and the crystalline second organic semiconductor layer (112), wherein the third organic semiconductor layer (110) is undoped, wherein the third organic semiconductor layer (110) has a third crystallinity that is less than or equal to the first crystallinity of the crystalline first organic semiconductor layer (108); and Forming a fourth organic semiconductor layer (116) on or above the crystalline second organic semiconductor layer (112), wherein the fourth organic semiconductor layer (116) has the same conduction type as the crystalline first organic semiconductor layer (108), wherein the fourth organic semiconductor layer (116) has a fourth crystallinity that is less than or equal to the second crystallinity of the crystalline second organic semiconductor layer (112). [14] Method (400) according to claim 13, wherein the crystalline first organic semiconductor layer (108) is formed with a first type of low molecular weight conjugated molecules, and wherein the crystalline second organic semiconductor layer (112) is formed with a second type of low molecular weight conjugated molecules, where the second type of conjugated molecules and the first type of conjugated molecules are the same or derivatives of the same type of conjugated molecules. [15] Method (400) according to claim 13 or 14, wherein the crystalline first organic semiconductor layer (108) comprises or is formed from rubrene or a derivative thereof; and / or wherein the crystalline second organic semiconductor layer (112) contains or is formed from rubrene or a derivative thereof. [16] Method (400) according to any one of claims 13 to 15, wherein the crystalline second organic semiconductor layer (112) is formed on the crystalline first organic semiconductor layer (108) by means of an epitaxy process, and / or wherein at least the crystalline second organic semiconductor layer (112) is formed using a solvent-free process. [17] Method (400) according to any one of claims 13 to 16, wherein at least the crystalline second organic semiconductor layer (112) has a second dopant which is introduced into the crystalline second organic semiconductor layer (112) by means of a co-evaporation process. [18] Method (400) according to any one of claims 13 to 17, wherein the substrate (102) has an organic crystal growth layer (106), wherein the crystalline first organic semiconductor layer (108) is formed directly on the organic crystal growth layer (106). [19] Method (400) according to any one of claims 13 to 18, wherein the third organic semiconductor layer (110) is directly adjacent to the first organic semiconductor layer (108) and / or the second organic semiconductor layer (112). [20] Method (400) for forming an organic bipolar transistor (100) comprising the method (400): Forming (410) a crystalline first organic semiconductor layer (108) on or over a substrate (102), wherein the crystalline first organic semiconductor layer (108) has a first conduction type; and Forming (420) a crystalline second organic semiconductor layer (112) on or above the crystalline first organic semiconductor layer (108), wherein the crystalline second organic semiconductor layer (112) has a second conduction type, wherein the first conduction type differs from the second conduction type, wherein the crystalline first organic semiconductor layer (108) has a first dopant and the crystalline second organic semiconductor layer (112) has a second dopant which differs from the first dopant; wherein the crystalline first organic semiconductor layer (108) exhibits a first crystallinity and the crystalline second organic semiconductor layer (112) exhibits a second crystallinity, where the second crystallinity is less than or equal to the first crystallinity; Forming a fourth organic semiconductor layer (116) on or above the crystalline second organic semiconductor layer (112), wherein the fourth organic semiconductor layer (116) has the same conduction type as the crystalline first organic semiconductor layer (108), wherein the fourth organic semiconductor layer (116) has a fourth crystallinity that is less than or equal to the second crystallinity of the crystalline second organic semiconductor layer (112); and Formation of a fifth organic semiconductor layer (114) between the crystalline second organic semiconductor layer (112) and the fourth organic semiconductor layer (116), wherein the fifth organic semiconductor layer (114) is undoped.

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