Michael Heuken

RWTH Aachen University · GaN-BET

A reliable and scalable transfer of 2D-TMDCs (two-dimensional transition metal dichalcogenides) from the growth substrate to a target substrate with high reproducibility and yield is a crucial step for device integration. In this work, we have introduced a scalable dry-transfer approach for 2D-TMDCs grown by MOCVD (metal-organic chemical vapor depo...

Research on thin-film technology-based radio frequency (RF) circuits is increasing to address the demand for transparent, wireless, and wearable consumer electronics applications. Owing to their excellent electronic and mechanical properties, two-dimensional materials (2DMs) are candidates with high potential for such applications. The 2DMs graphen...

Tungsten diselenide (WSe2) field-effect transistors (FETs) are promising for emerging electronics because of their tunable polarity, enabling complementary transistor technology, and their suitability for flexible electronics through material transfer. In this work, we demonstrate flexible p-type WSe2 FETs with absolute drain currents |ID| up to 7...

2D-TMDC layers are promising materials for ultra scaled field effect transistors. However, 2D-TMDC FETs suffer from high contact resistance. To study contact formation, we propose a novel tape-peel method to access the 2D/metal interface By characterization through the 2D layer, the thick and opaque metal film can be bypassed The insights obtained...

Organometallic complexes containing reactive alkali metals, such as lithium (Li), represent a promising material approach for electron injection layers and electron transport layers (EILs and ETLs) to enhance the performance of Organic Light-Emitting Diodes (OLEDs). 8-Quinolinolato Lithium (Liq) has shown remarkable potential as an EIL and ETL when...

Layered two-dimensional (2D) semiconductors have shown enhanced ion migration capabilities along their van der Waals (vdW) gaps and on their surfaces. This effect can be employed for resistive switching (RS) in devices for emerging memories, selectors, and neuromorphic computing. To date, all lateral molybdenum disulfide (MoS${_2}$)-based volatile...

Two-dimensional materials (2DMs) have been widely investigated because of their potential for heterogeneous integration with modern electronics. However, several major challenges remain, such as the deposition of high-quality dielectrics on 2DMs and the tuning of the 2DM doping levels. Here, we report a scalable plasma-enhanced atomic layer deposit...

A method for assessing the quality of electronic material properties of thin-film metal oxide semiconductor field-effect transistors (MOSFETs) is presented. By investigating samples with MOCVD-grown MoS${_2}$ channels exposed to atmospheric conditions, the existence of electron traps in MoS${_2}$ and at the interface between the gate insulator and...

Semiconducting transition metal dichalcogenides (TMDs) have gained significant attention as a gain medium for nanolasers, owing to their unique ability to be easily placed and stacked on virtually any substrate. However, the atomically thin nature of the active material in existing TMD lasers and the limited size due to mechanical exfoliation prese...

2D materials have received a lot of interest over the past decade. Especially van der Waals (vdW) 2D materials, such as transition metal dichalcogenides (TMDCs), and their heterostructures exhibit semiconducting properties that make them highly suitable for novel device applications. Controllable mixing and matching of the 2D materials with differe...

Transition metal dichalcogenides (TMDCs) are a promising class of two‐dimensional (2D) materials for flexible electronic applications due to their low integration temperature, good electronic properties, and excellent mechanical flexibility. Moreover, TMDCs offer the possibility of co‐integrating both n‐ and p‐type transistors on the same substrate...

Heterostacks formed by combining two-dimensional materials show novel properties which are of great interest for new applications in electronics, photonics and even twistronics, the new emerging field born after the outstanding discoveries on twisted graphene. Here, we report the direct growth of tin nanosheets at the two-dimensional limit via mole...

Two-dimensional (2D) materials are considered for numerous applications in microelectronics, although several challenges remain when integrating them into functional devices. Weak adhesion is one of them, caused by their chemical inertness. Quantifying the adhesion of 2D materials on three-dimensional surfaces is, therefore, an essential step towar...

Semiconducting transition metal dichalcogenides (TMDs) have gained significant attention as a gain medium for nanolasers, owing to their unique ability to be easily placed and stacked on virtually any substrate. However, the atomically thin nature of the active material in existing TMD lasers and the limited size due to mechanical exfoliation prese...

Abstract: Extensive research into two-dimensional transition metal dichalcogenides (2D-TMDCs) over the past decade has paved the way for the development of (opto)electronic devices with enhanced performance and novel capabilities. To realize devices based on 2D-TMDC layers, compatible and optimized technologies such as layer transfer and photolitho...

Abstract: Metal-organic chemical vapor deposition (MOCVD) is a key method for scalable synthesis of two-dimensional transition metal dichalcogenide (2D-TMDC) layers. However, it faces several challenges, such as the unintentional co-deposition of carbon impurities resulting from the pyrolysis of metal-organic precursors. This study investigates the...

Epitaxial growth has become a promising route to achieve highly crystalline continuous two-dimensional layers. However, high-quality layer production with expected electrical properties is still challenging due to the defects induced by the coalescence between imperfectly aligned domains. In order to control their intrinsic properties at the device...

Two-dimensional transition metal dichalcogenides (2D-TMDCs) have promising (opto)electronic properties, making them attractive materials for various electronic devices. Transfer of 2D-TMDCs from a growth substrate to a target substrate is a crucial step for device integration. In this work, we present a novel dry transfer technique, which is superi...

Heterostacks formed by combining two-dimensional materials show novel properties which are of great interest for new applications in electronics, photonics and even twistronics, the new emerging field born after the outstanding discoveries on twisted graphene. Here, we report the direct growth of tin nanosheets at the two-dimensional limit via mole...

Epitaxial growth has become a promising route to achieve highly crystalline continuous two-dimensional layers. However, high-quality layer production with expected electrical properties is still challenging due to the defects induced by the coalescence between imperfectly aligned domains. In order to control their intrinsic properties at the device...

Semiconducting transition metal dichalcogenides (TMDs) have gained significant attention as a gain medium for nanolasers, owing to their unique ability to be easily placed and stacked on virtually any substrate. However, the atomically thin nature of the active material in existing TMD nanolasers presents a challenge, as their limited output power...

Transition metal dichalcogenide (TMDC) monolayers with their direct band gap in the visible to near-infrared spectral range have emerged over the past years as highly promising semiconducting materials for optoelectronic applications. Progress in scalable fabrication methods for TMDCs like metal-organic chemical vapor deposition (MOCVD) and the amb...

Focused ion beam (FIB) is an effective tool for precise nanoscale fabrication. It has recently been employed to tailor defect engineering in functional nanomaterials such as two-dimensional transition metal dichalcogenides (TMDCs), providing desirable properties in TMDC-based optoelectronic devices. However, the damage caused by the FIB irradiation...

Structural defects in transition metal dichalcogenide (TMDC) monolayers (ML) play a significant role in determining their (opto)electronic properties, triggering numerous efforts to control defect densities during material growth or by post-growth treatments. Various types of TMDC have been successfully deposited by MOCVD (metal-organic chemical va...

In this work, multi-layer PECVD SiNx/SiNx and SiNx/SiOy passivations are developed featuring very high soft breakdown strength and tunable stress properties, which would allow for stress engineering and wafer bow minimization. AlGaN/GaN-on-Si wafers (150 mm) with very low initial bow (< 5 μm) are processed in a CMOS compatible manner. The effect of...

Metal-free chemical vapor deposition (CVD) of single-layer graphene (SLG) on c-plane sapphire has recently been demonstrated for wafer diameters of up to 300 mm, and the high quality of the SLG layers is generally characterized by integral methods. By applying a comprehensive analysis approach, distinct interactions at the graphene-sapphire interfa...

Focused ion beam (FIB) has been used as an effective tool for precise nanoscale fabrication. It has recently been employed to tailor defect engineering in functional nanomaterials such as two-dimensional transition metal dichalcogenides (TMDCs), providing desirable properties in TMDC-based optoelectronic devices. However, the damage caused by the F...

A promising strategy toward ultrathin, sensitive photodetectors is the combination of a photoactive semiconducting transition-metal dichalcogenide (TMDC) monolayer like MoS2 with highly conductive graphene. Such devices often exhibit a complex and contradictory photoresponse as incident light can trigger both photoconductivity and photoinduced deso...

Metal–organic chemical vapour deposition (MOCVD) has become one of the most promising techniques for the large-scale fabrication of 2D transition metal dichalcogenide (TMDC) materials. Despite efforts devoted to the development of MOCVD for TMDC monolayers, the whole picture of the growth process has not been fully unveiled yet. In this work, we em...

We demonstrate the design, fabrication, and characterization of wafer-scale, zero-bias power detectors based on two-dimensional MoS2 field effect transistors (FETs). The MoS2 FETs are fabricated using a wafer-scale process on 8 μm thick Polyimide film, which in principle serves as flexible substrate. The performances of two CVD-MoS2 sheets, grown w...

We demonstrate the design, fabrication, and characterization of wafer-scale, zero-bias power detectors based on two-dimensional MoS$_2$ field effect transistors (FETs). The MoS$_2$ FETs are fabricated using a wafer-scale process on 8 $\mu$m thick polyimide film, which in principle serves as flexible substrate. The performances of two CVD-MoS$_2$ sh...

We investigate the effectiveness of laser-induced treatment as compared to rapid-thermal annealing (RTA) for the activation of p-type dopant in Mg-doped GaN layers. The study is based on a wide set of analytical techniques, including resistivity measurements, atomic force microscopy, scanning emission microscopy (SEM), dynamic secondary ion mass sp...

This paper reviews recent progress and key challenges in process and reliability for high-performance vertical GaN transistors and diodes, focusing on the 200 mm CMOS-compatible technology. We particularly demonstrated the potential of using 200 mm diameter CTE matched substrates for vertical power transistors, and gate module optimizations for dev...

2D semiconductors based on transition metal dichalcogenides are highly promising for ultrathin photodetectors due to their thickness in the nanometer range and their exceptional light absorption properties. To enable efficient separation of optically generated electron–hole pairs heterostructures have to be implemented, which are usually prepared b...

In this work, the dynamic behavior of gallium nitride on silicon high electron mobility transistors (GaN/Si HEMT) with carbon doped buffer is modeled using a finite state machine embedded into the core Advanced Spice Model for High Electron Mobility Transistor (ASM-HEMT). The model is based on the physics of trapping and detrapping of electrons in...

This paper reviews recent progress and key challenges in process and reliability for high-performance vertical GaN transistors and diodes, focusing on the 200 mm CMOS-compatible technology. We particularly demonstrated the potential of using 200 mm diameter CTE matched substrates for vertical power transistors, and gate module optimizations for dev...

CsPbBr 3 represents a highly attractive material for perovskite light-emitting diodes (PeLEDs) in the green spectral range. However, the lack of deposition tools for reproducible and scalable growth of perovskite films is one of the major obstacles hindering PeLED commercialization. Here, we employ the highly scalable showerhead-assisted chemical v...

In this work, metal organic vapor phase epitaxy (MOVPE) is employed for selective-area growth (SAG) of undoped and lightly n-doped GaN micropillars on masked GaN-on-sapphire templates. In micropillar geometry, the limits of GaN drift layer thickness in hetereoepitaxial Schottky diodes are expected to be significantly pushed upwards. This is an impo...

A new technique is proposed, verified, and described for measuring photosensitivity spectra of semiconductor materials and devices in the wavelength range of 200-4100 nm utilizing an innovative setup termed “Polychromator” with a system of cut-off optical filters that provide a sharp edge of the spectrum of radiation impinging on the sample. The me...

GaN power ICs on engineered substrates of Qromis substrate technology (QST) are promising for future power applications, thanks to the reduced parasitics, thermally matched substrate of poly-AlN, high thermal conductivity, and high mechanical yield in combination with thick GaN buffer layers. In this article, we will elaborate in detail on epitaxy,...

Strong covalent in‐plane bonds and a tiny thickness in the nanometer range make two‐dimensional (2D) materials ideally suited for flexible electronic or optoelectronic applications. Despite this exciting perspective, only a few prototypes of such flexible devices—photodetectors and transistors—have been reported until now. The first large‐area flex...

The aim of the ongoing GIMMIK research project is to expand graphene technology for electronic components and bring it up to production standards. In the GIMMIK project, the production of graphene layers is to be evaluated for the first time under industrial conditions. The weak points in the corresponding processing are identified and ways to elim...

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are seen as promising candidates for flexible electronic and optoelectronic devices due to their high tensile strength and favorable optical properties. Molybdenum disulfide (MoS2) is a benchmark material for TMDCs, which has already been studied extensively. Here, we report on highly re...

We have analysed electrical properties of extended defects and interfaces in fully strained and partially relaxed InxGa1-xN/GaN heterostructures by means of Kelvin probe force microscopy and surface photovoltage spectroscopy. The study highlights the role of indium incorporation and Si doping levels on the charge state of extended defects including...

In the last years, perovskite solar cells have attracted great interest in photovoltaic (PV) research due to their possibility to become a highly efficient and low-cost alternative to silicon solar cells. Cells based on the widely used Pb-containing perovskites have reached power conversion efficiencies (PCE) of more than 20 %. One of the major hur...

In this article, an optimized carbon-doped AlGaN/AlN super-lattice (SL) buffer structure for GaN-based high electron mobility transistors, grown on 200-mm Si wafers is demonstrated. The resulting transistor structure features: 1) maximum vertical breakdown strength as high as 2.72 MV/cm, 2) vertical breakdown voltages (BVs) above 1.2 kV, 3) lateral...

Most publications on (opto)electronic devices based on 2D materials rely on single monolayers embedded in classical 3D semiconductors, dielectrics and metals. However, heterostructures of different 2D materials can be employed to tailor the performance of the 2D components by reduced defect densities, carrier or exciton transfer processes and impro...