Silicon is the standard material for active electronic devices in the chip industry, as well as for tracking and vertex detectors in particle physics. Other solid-state materials, such as artificial (CVD) diamond, have been studied but could not be manufactured cost-effectively on a large scale due to lack of commercial interest.
The semiconductor industry gained interest in silicon carbide (SiC) recently as a substitute for silicon in power semiconductor devices. Typically these are used in frequency converters for photovoltaics and for the drive train in electric cars. This widespread use has brought the quality of that material to a level similar to silicon, enabling the commercial availability of high-purity and large-area wafers.
SiC offers several advantages compared to Si, that make it an attractive detector material. These include a higher dislocation energy of atoms in the crystal than in silicon, making SiC potentially more radiation resistant. The high thermal conductivity and very low dark currents, even after high irradiation fluences, would eliminate the need for device cooling.
For these reasons, SiC and other wide-bandgap materials are mentioned as an alternative base material for use as a particle detector in the ECFA Detector R&D Roadmap document.
With a bandgap of 3.26 eV, which is in between silicon and diamond, it combines the properties of both materials. Nevertheless, some unique features are less explored and known. SiC has also not yet been properly modeled in TCAD, and many parameters have not been studied.
TCAD Simulations and Models
With the constantly increasing computing power, many development steps are shifted to software simulations, so that the design of new and optimized particle detectors can be performed more cost-efficiently and resource-saving in the computer. For semiconductor detectors, we use so-called TCAD simulation programs, which were originally developed for the chip industry. In addition to Synopsys Sentaurus TCAD, which is commonly used in detector development, we also use software from the Austrian company Global TCAD Solutions, with whom we are collaborating as part of an FFG-funded project.
TCAD simulations are also important tools for the design and optimization of silicon carbide detectors. This requires simulation models that describe the physical properties of the material. However, these parameters are not yet as well known and verified for SiC, as they are for the much more widely used silicon. Therefore, we use our measuring equipment and probe stations in the clean room to experimentally determine these parameters by measurements on prototype SiC sensors. These serve as input for the TCAD simulation models.
After parameter determination and model building, we use TCAD to simulate novel particle detectors, e.g., a SiC sensor with built-in amplifier, so-called Low Gain Avalanche Detectors (LGADs), or monolithic pixel detectors based on CMOS processes on SiC base material.
Experimental model validation
Text follows about:
- IV and CV measurements
- TCT setup for
- Time resolution
- Charge collection
- Neutron irradiation
