Wide-bandgap semiconductor

Wide-bandgap semiconductors (also known as WBG semiconductors or WBGSs) are semiconductor materials which have a larger band gap than conventional semiconductors. Conventional semiconductors like silicon have a bandgap in the range of 0.6 – 1.5 electronvolt (eV), whereas wide-bandgap materials have bandgaps in the range above 2 eV. Generally, wide-bandgap semiconductors have electronic properties which fall in between those of conventional semiconductors and insulators. Wide-bandgap semiconductors permit devices to operate at much higher voltages, frequencies, and temperatures than conventional semiconductor materials like silicon and gallium arsenide. They are the key component used to make short-wavelength (green-UV) LEDs or lasers, and are also used in certain radio frequency applications, notably military radars. Their intrinsic qualities make them suitable for a wide range of other applications, and they are one of the leading contenders for next-generation de

Crystal Phase Engineering in III-V Semiconductor Films: from Epitaxy to Devices

Philipp Staudinger

Crystal phase engineering is an exciting pathway to enhance the properties of conventional semiconductors. Metastable SiGe presents a direct band gap well suited for optical devices whereas wurtzite (WZ) phosphide alloys enable efficient light emission in the green spectral range. Availability of these materials could profoundly impact electronics as well as solid-state lighting industries. However, their synthesis in high quality and beyond nanowire size constraints remained elusive, hampering both scientific and commercial exploitation. In this thesis, we develop new approaches for metastable film growth to enable a platform for robust material characterization and device fabrication. Metal-organic vapor phase epitaxy is used to grow pure WZ nanowires and fins. To obtain planar layers, we explore two extensions of this well-known technique. The first one is based on conformal epitaxy and enables the use of standard (001)-oriented substrates. In this way, we achieve the controlled concurrent epitaxy of stable and metastable InP. We further propose a variation of this approach by using a nanowire as seed. This establishes a clear route for the synthesis of a large range of materials as is exemplarily demonstrated for WZ GaAs films. For the second technique we explore a method to enforce epitaxial lateral overgrowth on (111)A-oriented substrates. This allows to deposit pure WZ InP layers on insulator exceeding areas of 100 µm2, the largest ever demonstrated. We conceive a nucleation-based model and argue on a fundamental size limitation of metastable film epitaxy. Further advancement of this process allows to directly grow metastable micro- and nanostructures, which are optically isolated from the substrate. The high quality and shape-control of these crystals enables room-temperature lasing in WZ InP microdisks. This thesis demonstrates the successful development of new concepts to synthesize metastable semiconductors with pure crystalline phase and dimensions tailored towards planar device fabrication. We expect our findings to significantly contribute to the realization of crystal phase engineered electronic and optoelectronic devices.

EPFL2020

Advanced power electronic devices based on Gallium Nitride (GaN)

Bin Lu, Elison de Nazareth Matioli, Yuhao Zhang

It is the most exciting time for power electronics in decades. The combination of new applications, such as microinverters, electric vehicles and solid state lighting, with the new opportunities brought by wide bandgap semiconductors is expected to significantly increase the reach and impact of power electronics. This paper describes some of the recent advances on developing power devices based on Gallium Nitride (GaN), the key design constrains, and the process to take a new device material and structure from the research laboratory of universities to full commercialization. © 2015 IEEE.

IEEE2015

Crystal Phase Engineering in III-V Semiconductor Films: from Epitaxy to Devices

Philipp Staudinger

EPFL2020

Femtosecond dynamics of electron transfer in the photosensitization of wide band gap semiconductors

Crystal Phase Engineering in III-V Semiconductor Films: from Epitaxy to Devices

Advanced power electronic devices based on Gallium Nitride (GaN)

Crystal Phase Engineering in III-V Semiconductor Films: from Epitaxy to Devices

Femtosecond dynamics of electron transfer in the photosensitization of wide band gap semiconductors

Advanced power electronic devices based on Gallium Nitride (GaN)