Mark A. Anders

Relationship Between the 4H-SiC/SiO 2 Interface Structure and Electronic Properties Explored by Electrically Detected Magnetic Resonance

In this paper, an exceptionally sensitive form of electron paramagnetic resonance called electrically detected magnetic resonance (EDMR) is utilized to investigate performance limiting imperfections at and very near the interface of 4H-silicon carbide MOSFETs. EDMR measurements are made over an extremely wide range of frequencies, 16 GHz-350 MHz. Multiple interface/near interface defects are identified and strong evidence for significant disorder at the interface region is presented.

Vectorized magnetometer for space applications using electrical readout of atomic scale defects in silicon carbide

Magnetometers are essential for scientific investigation of planetary bodies and are therefore ubiquitous on missions in space. Fluxgate and optically pumped atomic gas based magnetometers are typically flown because of their proven performance, reliability, and ability to adhere to the strict requirements associated with space missions. However, their complexity, size, and cost prevent their applicability in smaller missions involving cubesats. Conventional solid-state based magnetometers pose a viable solution, though many are prone to radiation damage and plagued with temperature instabilities. In this work, we report on the development of a new self-calibrating, solid-state based magnetometer which measures magnetic field induced changes in current within a SiC pn junction caused by the interaction of external magnetic fields with the atomic scale defects intrinsic to the semiconductor. Unlike heritage designs, the magnetometer does not require inductive sensing elements, high frequency radio, and/or optical circuitry and can be made significantly more compact and lightweight, thus enabling missions leveraging swarms of cubesats capable of science returns not possible with a single large-scale satellite. Additionally, the robustness of the SiC semiconductor allows for operation in extreme conditions such as the hot Venusian surface and the high radiation environment of the Jovian system.

Are dangling bond centers important interface traps in 4H-SiC metal oxide semiconductor field effect transistors?

Silicon carbide (SiC) based metal-oxide-semiconductor field-effect transistors (MOSFETs) have great promise in high power and high temperature applications. Unfortunately, effective channel mobilities remain disappointingly low, typically about 30 cm2/Vs. A major contributor to the disappointing effective channel mobilities is the presence of substantial densities of interface traps at the SiC/SiO2 interface. Many investigators have invoked silicon or carbon dangling bonds to be the dominating source of these interface defects, but very little, if any, direct experimental evidence exists to support this assumption in the SiC/SiO2 system. Cantin et al. [Phys. Rev. Lett. 92, 1 (2004)] have used conventional electron paramagnetic resonance measurements on porous oxidized SiC structures to measure the g tensor for the SiC/SiO2 interface carbon dangling bond. These results provide a particularly straightforward means to search for the presence of carbon dangling bonds in fully processed SiC MOSFETs using elect...

Ionizing Radiation Effects in 4H-SiC nMOSFETs Studied With Electrically Detected Magnetic Resonance

Electrically detected magnetic resonance (EDMR) measurements of 4H-SiC/SiO2 metal-oxide-semiconductor field-effect transistors (MOSFETs) show large changes in the EDMR induced by gamma irradiation, indicating substantial changes in interface structure but, surprisingly, no generation of interface dangling bond defects. Our results indicate substantial fundamental atomic scale differences between radiation responses of Si/SiO2 based MOSFETs and SiC/SiO2 based MOSFETs.

Magnetic Field Sensing with Atomic Scale Defects in SiC Devices

Silicon carbide (SiC) is well known by the semiconductor industry to have significant potential for electronics used in high temperature environments due to its wide bandgap. It is not so well-known, however, that SiC also has great potential in the area of magnetic field sensing. Using the recently demonstrated zero-field spin dependent recombination (SDR) phenomenon that naturally arises in SiC based devices, near-zero magnetic field measurements can be made with moderately high sensitivity.

Multi-resonance frequency spin dependent charge pumping and spin dependent recombination - applied to the 4H-SiC/SiO2 interface

We report on a new electrically detected magnetic resonance (EDMR) approach involving spin dependent charge pumping (SDCP) and spin dependent recombination (SDR) at high (K band, about 16 GHz) and ultra-low (360 and 85 MHz) magnetic resonance frequencies to investigate the dielectric/semiconductor interface in 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs). A comparison of SDCP and SDR allows for a comparison of deep level defects and defects with energy levels throughout most of the bandgap. Additionally, a comparison of high frequency and ultra-low frequency measurements allows for (1) the partial separation of spin-orbit coupling and hyperfine effects on magnetic resonance spectra, (2) the observation of otherwise forbidden half-field effects, which make EDMR, at least, in principle, quantitative, and (3) the observation of Breit-Rabi shifts in superhyperfine measurements. (Observation of the Breit-Rabi shift helps in both the assignment and the measurement of superhyperfine parame...

A Surprising Result: “Bulk” SiC Defects in the Negative Bias Instability in 4H-SiC MOSFETs

We utilize electrically detected magnetic resonance and “on-the-fly” elevated temperature stressing to examine the effects of negative bias temperature stress on defects within the “bulk” SiC, that is, below the SiC/SiO2 interface. We observe generation of two temperature-dependent defects; one has a two (or three) line spectrum with lines separated by about 61 (30) Gauss when the SiC/SiO2 interface is perpendicular to the magnetic field and very slightly less, about 59 (30) Gauss when the SiC/SiO2 interface is parallel to the field. The second spectrum has a single line with zero-crossing g = 2.0118 when the magnetic field is nearly perpendicular to the SiC/SiO2 interface; the g-value drops to about 2.0016 with the field parallel to the SiC/SiO2 interface. We also observe strong evidence for hydrogen motion within the “bulk” SiC, as both spectra broaden significantly at elevated temperature, with broadening at both high and low fields and frequencies.

Bias temperature instabilities in 4H SiC metal oxide semiconductor field effect transistors: Insight provided by electrically detected magnetic resonance

Abstract We present insight with regard to the physical mechanisms of negative bias temperature instabilities (NBTI) in 4H SiC based metal oxide semiconductor field effect transistors (MOSFETs) based upon electrically detected magnetic resonance measurements (EDMR). Most of this insight results from EDMR studies not directly focused upon NBTI but studies more broadly focused upon two fundamental questions. (1) What as-processed defects are present at and near the SiC/oxide interface? (2) How does the presence of oxide charge alter electrically active defects at the SiC/dielectric interface? We compare the SiC results to magnetic resonance studies of bias temperature instabilities in silicon based devices. Although our analysis admittedly provides only a partial understanding of the phenomena in SiC devices, the analysis does allow for some reasonably definitive conclusions. The NBTI phenomena in 4H SiC MOSFETs are certainly different than in Si based MOSFETs. (1) Interface dangling bonds do not appear to play a significant role in SiC MOSFET interface traps under multiple circumstances, suggesting strongly that they are not significant contributors to NBTI. (2) Although oxide defects, almost certainly including the well-known E′ family of oxide traps, play an important role in SiC device NBTI, other defects, surprisingly including defects within the SiC substrate, are also involved.

The Effect of Nitrogen on the 4H-SiC/SiO2 Interface Studied with Variable Resonance Frequency Spin Dependent Charge Pumping

In this work, we study the effects of NO anneals on the interface of 4H-SiC MOSFETs via spin dependent charge pumping, an electrically detected magnetic resonance technique. We make measurements at high and ultra-low resonance frequencies. Our results indicate that the NO anneals both change the silicon vacancy energy levels as well as induces disorder at the interface. In addition, our results indicate that the changes in energy levels involve N atoms very close to VSi sites.