High Channel Mobility 4H-SiC MOSFETs

2006 ◽  
Vol 527-529 ◽  
pp. 961-966 ◽  
Author(s):  
Einar Ö. Sveinbjörnsson ◽  
G. Gudjónsson ◽  
Fredrik Allerstam ◽  
H.Ö. Ólafsson ◽  
Per Åke Nilsson ◽  
...  
Keyword(s):  
Field Effect ◽  
Phonon Scattering ◽  
Conduction Band Edge ◽  
Clear Correlation ◽  
Stable Operation ◽  
Interface Traps ◽  
Field Effect Mobility ◽  
Threshold Voltage Shift ◽  
Mos Capacitors ◽  
Positive Threshold

We report investigations of MOS and MOSFET devices using a gate oxide grown in the presence of sintered alumina. In contrast to conventionally grown dry or wet oxides these oxides contain orders of magnitude lower density of near-interface traps at the SiO2/SiC interface. The reduction of interface traps is correlated with enhanced oxidation rate. The absence of near-interface traps makes possible fabrication of Si face 4H-SiC MOSFETs with peak field effect mobility of about 150 cm2/Vs. A clear correlation is observed between the field effect mobility in n-channel MOSFETs and the density of interface states near the SiC conduction band edge in n-type MOS capacitors. Stable operation of such normally-off 4H-SiC MOSFET transistors is observed from room temperature up to 150°C with positive threshold voltage shift less than 1 V. A small decrease in current with temperature up to 150°C is related to a decrease in the field effect mobility due to phonon scattering. However, the gate oxides contain sodium, which originates from the sintered alumina, resulting in severe device instabilities during negative gate bias stressing.

Gamma Irradiation Effects on 4H-SiC MOS Capacitors and MOSFETs

2006 ◽  
Vol 527-529 ◽  
pp. 1063-1066 ◽  
Author(s):  
Ayayi Claude Ahyi ◽  
S.R. Wang ◽  
John R. Williams
Keyword(s):  
Field Effect ◽  
Gamma Dose ◽  
Interface Traps ◽  
Valence Band Edge ◽  
Field Effect Mobility ◽  
Irradiation Effects ◽  
Mos Capacitors ◽  
Channel Mobility ◽  
Radiation Induced ◽  
Radiation Tolerant

The effects of gamma radiation on field effect mobility and threshold voltage have been studied for lateral n-channel 4H-SiC MOSFETs passivated with nitric oxide. MOS capacitors (n and p) and n-channel lateral MOSFETs were irradiated unbiased (floating contacts) for a total gamma dose of 6.8Mrad (Si). The MOS capacitors were used to study the radiation-induced interface traps and fixed oxide charge that affect the performance of the MOSFETs. Radiationinduced interface traps were observed near the SiC valence band edge and just above mid-gap, and field effect channel mobility was reduced by 18-20% following irradiation. Even so, 4HMOSFETs appear to be more radiation tolerant than Si devices.

High-Mobility SiC MOSFETs with Alkaline Earth Interface Passivation

2016 ◽  
Vol 858 ◽  
pp. 671-676 ◽  
Author(s):  
Daniel J. Lichtenwalner ◽  
Vipindas Pala ◽  
Brett A. Hull ◽  
Scott Allen ◽  
John W. Palmour
Keyword(s):  
Nitric Oxide ◽  
Field Effect ◽  
Alkaline Earth ◽  
Phonon Scattering ◽  
Breakdown Strength ◽  
Field Effect Transistors ◽  
Oxide Semiconductor ◽  
Field Effect Mobility ◽  
Channel Mobility ◽  
Alkaline Earth Elements

Alkaline earth elements Sr and Ba provide SiO2/SiC interface conditions suitable for obtaining high channel mobility metal-oxide-semiconductor field-effect-transistors (MOSFETs) on the Si-face (0001) of 4H-SiC, without the standard nitric oxide (NO) anneal. The alkaline earth elements Sr and Ba located at/near the SiO2/SiC interface result in field-effect mobility (μFE) values as high as 65 and 110 cm2/V.s, respectively, on 5×1015 cm-3 Al-doped p-type SiC. As the SiC doping increases, peak mobility decreases as expected, but the peak mobility remains higher for Ba interface layer (Ba IL) devices compared to NO annealed devices. The Ba IL MOSFET field-effect mobility decreases as the temperature is increased to 150 °C, as expected when mobility is phonon-scattering-limited, not interface-trap-limited. This is in agreement with measurements of the interface state density (DIT) using the high-low C-V technique, indicating that the Ba IL results in lower DIT than that of samples with nitric oxide passivation. Vertical power MOSFET (DMOSFET) devices (1200V, 15A) fabricated with the Ba IL have a 15% lower on-resistance compared to devices with NO passivation. The DMOSFET devices with a Ba IL maintain a stable threshold voltage under NBTI stress conditions of-15V gate bias stress, at 150 °C for 100hrs, indicating no mobile ions. Secondary-ion mass-spectrometry (SIMS) analysis confirms that the Sr and Ba remain predominantly at the SiO2/SiC interface, even after high temperature oxide annealing, consistent with the observed high channel mobility after these anneals. The alkaline earth elements result in enhanced SiC oxidation rate, and the resulting gate oxide breakdown strength is slightly reduced compared to NO annealed thermal oxides on SiC.

Comparison of channel mobility and oxide properties of MOSFET devices on Si-face (0001) and A-face (11-20) 4H-SiC

2014 ◽  
Vol 1693 ◽  
Author(s):  
Daniel J. Lichtenwalner ◽  
Lin Cheng ◽  
Scott Allen ◽  
John W. Palmour ◽  
Aivars Lelis ◽  
...  
Keyword(s):  
Valence Band ◽  
Barrier Height ◽  
Field Effect ◽  
Phonon Scattering ◽  
Electron Tunneling ◽  
Negative Temperature ◽  
Field Effect Mobility ◽  
Channel Mobility ◽  
P Type ◽  
And Control

ABSTRACTIn this report we present results comparing lateral MOSFET properties of devices fabricated on Si-face (0001) and A-face (11-20) 4H-SiC, with nitric oxide passivation anneals. We observe a field-effect mobility of 33 cm2/V.s on p-type 5×1015 doped Si-face. These devices have a peak field-effect mobility which increases with temperature, indicative of a channel mobility limited by coulomb scattering. On 1×1016 p-type A-face SiC, the peak channel mobility is observed to be 80 cm2/V.s, with a negative temperature dependence, indicating that phonon-scattering effects dominate, with a much lower density of shallow acceptor traps. This > 2x higher channel mobility would result in a substantial decrease in on-resistance, hence lower power losses, for 4H-SiC power MOSFETs with voltage ratings below 2 kV. However, MOS C-V and gate leakage measurements indicate very different oxide and interface quality on each SiC face. For example, the Fowler-Nordheim (FN) conduction-band (CB) barrier height for electron tunneling at the SiO2/SiC interface is 2.8 eV on Si-face SiC, while it is 2.5 eV or less on A-face SiC. For the valence-band side, the effective FN barrier height at the valence-band (VB) side of only 1.6 eV on A-face SiC, while the VB barrier height is about 3.1 eV on Si-face SiC. Moreover, C-V of the MOS gate on A-face indicates the presence of a high-density of deep hole traps. It is apparent that oxides on alternative crystal faces, very promising in terms of channel mobility, require further study for complete understanding and control of the interface properties.

Effect of NH3 Post-Oxidation Annealing on Flatness of SiO2/SiC Interface

2013 ◽  
Vol 740-742 ◽  
pp. 723-726 ◽  
Author(s):  
Narumasa Soejima ◽  
Taishi Kimura ◽  
Tsuyoshi Ishikawa ◽  
Takahide Sugiyama
Keyword(s):  
Nitrous Oxide ◽  
Field Effect ◽  
Inversion Layer ◽  
Trap Density ◽  
Interface Trap Density ◽  
Interface Trap ◽  
Field Effect Mobility ◽  
Interfacial Roughness ◽  
Cross Sectional ◽  
Mos Capacitors

We investigated the effects of the post-oxidation annealing (POA) atmosphere on the electrical properties and interfacial roughness of SiO2 deposited on a 4H-SiC (0001) face and SiC. POA in ammonia (NH3) gave MOS capacitors with a lower interface trap density and n-channel MOSFETs with higher field-effect mobility than POA in nitrous oxide (N2O) or nitrogen (N2). In contrast, POA in N2O gave a lower interface trap density than POA in N2, but it gave the lowest field-effect mobility of all the samples. Cross-sectional TEM observations revealed that N2O POA gave a higher interfacial roughness than NH3 POA. We thus considered that N2O POA degraded the inversion-layer mobility due to increased roughness scattering.

Correlation between Field Effect Mobility and Accumulation Conductance at 4H-SiC MOS Interface with Barium

2018 ◽  
Vol 924 ◽  
pp. 477-481
Author(s):  
Kosuke Muraoka ◽  
Seiji Ishikawa ◽  
Hiroshi Sezaki ◽  
Tomonori Maeda ◽  
Shinichiro Kuroki
Keyword(s):  
Linear Correlation ◽  
Field Effect ◽  
Interface State ◽  
State Density ◽  
Interface State Density ◽  
Field Effect Mobility ◽  
Mos Capacitors

A correlation between field effect mobility and an accumulation conductance has been investigated at 4H-SiC MOS interface with barium. 4H-SiC n-channel MOSFETs and n-type MOS capacitors were fabricated with a barium-introduced SiO2and a conventional dry SiO2. The field effect mobility was enhanced by introducing the barium-introduced SiO2. It is found that there is a linear correlation between the mobility and the accumulation conductance. The MOS interface of the barium-introduced SiO2had a lower interface state density of 2×1011cm-2eV-1than that of the conventional dry SiO2.

scholarly journals Mechanical Stress Stability of Flexible Amorphous Zinc Tin Oxide Thin-Film Transistors

2021 ◽  
Vol 2 ◽  
Author(s):  
Oliver Lahr ◽  
Max Steudel ◽  
Holger von Wenckstern ◽  
Marius Grundmann
Keyword(s):  
Electrical Properties ◽  
Tin Oxide ◽  
Flexible Electronics ◽  
Field Effect ◽  
Tensile Strain ◽  
Room Temperature ◽  
Oxide Thin Film ◽  
Field Effect Mobility ◽  
Threshold Voltage Shift ◽  
Zinc Tin Oxide

Due to their low-temperature processing capability and ionic bonding configuration, amorphous oxide semiconductors (AOS) are well suited for applications within future mechanically flexible electronics. Over the past couple of years, amorphous zinc tin oxide (ZTO) has been proposed as indium and gallium-free and thus more sustainable alternative to the widely deployed indium gallium zinc oxide (IGZO). The present study specifically focuses on the strain-dependence of elastic and electrical properties of amorphous zinc tin oxide thin-films sputtered at room temperature. Corresponding MESFETs have been compared regarding their operation stability under mechanical bending for radii ranging from 5 to 2 mm. Force-spectroscopic measurements yield a plastic deformation of ZTO as soon as the bending-induced strain exceeds 0.83 %. However, the electrical properties of ZTO determined by Hall effect measurements at room temperature are demonstrated to be unaffected by residual compressive and tensile strain up to 1.24 %. Even for the maximum investigated tensile strain of 1.26 %, the MESFETs exhibit a reasonably consistent performance in terms of current on/off ratios between six and seven orders of magnitude, a subthreshold swing around 350 mV/dec and a field-effect mobility as high as 7.5 cm2V−1s−1. Upon gradually subjecting the transistors to higher tensile strain, the channel conductivity steadily improves and consequently, the field-effect mobility increases by nearly 80 % while bending the devices around a radius of 2 mm. Further, a reversible threshold voltage shift of about −150 mV with increasing strain is observable. Overall, amorphous ZTO provides reasonably stable electrical properties and device performance for bending-induced tensile strain up to at least 1.26 % and thus represent a promising material of choice considering novel bendable and transparent electronics.

SiC and GaN MOS Interfaces – Similarities and Differences

2010 ◽  
Vol 645-648 ◽  
pp. 473-478 ◽  
Author(s):  
T. Paul Chow
Keyword(s):  
Carrier Concentration ◽  
Threshold Voltage ◽  
Field Effect ◽  
Gate Oxide ◽  
Electron Trapping ◽  
Electrical Characteristics ◽  
Subthreshold Slope ◽  
Field Effect Mobility ◽  
Mos Capacitors ◽  
Similarities And Differences

We have comparatively characterized the electrical characteristics of 4H-SiC and 2H-GaN MOS capacitors and FETs. While progressive refinement of gate oxide processes, notably with NO anneal, has resulted in better threshold voltage control, reduced subthreshold slope and higher field-effect mobility for 4H-SiC MOSFETs, we have recently reported more superior MOS parameters for 2H-GaN MOSFETs. In addition, we have performed MOS-gated Hall measurements to extract the intrinsic carrier concentration and MOS mobility, indicating that both less channel electron trapping and scattering take place in 2H-GaN MOSFETs.

Progress in GaN MOSFET Technology

2008 ◽  
Vol 600-603 ◽  
pp. 1263-1268 ◽  
Author(s):  
T. Paul Chow ◽  
W. Huang ◽  
T. Khan ◽  
K. Matocha ◽  
Y. Wang
Keyword(s):  
Field Effect ◽  
Interface State ◽  
Orientation Dependence ◽  
State Density ◽  
Interface State Density ◽  
Field Effect Mobility ◽  
Mos Capacitors ◽  
Enhancement Mode ◽  
Current Collapse ◽  
Non Destructive

GaN MOS capacitors were characterized to optimize the electric properties of SiO2/GaN interface. With optimized anneal conditions, an interface state density of 3.8×1010/cm2-eV was estimated at 0.19 eV near the conduction band and decreases deeper into the band gap. Enhancement-mode GaN MOSFETs were experimentally demonstrated on both p and n GaN epilayer with record high field-effect mobility of 167 cm2/V-s. Lateral RESURF-type GaN MOSFETs exhibit non-destructive high voltage (up to 940V) blocking capabilities. Other characterization including mobility orientation dependence, MOS-gated Hall mobility, current collapse and an NMOS inverter utilizing E/D mode GaN MOSFETs have also been experimentally demonstrated.

Investigation of Oxide Films Prepared by Direct Oxidation of C-Face 4H-SiC in Nitric Oxide

2010 ◽  
Vol 645-648 ◽  
pp. 515-518 ◽  
Author(s):  
Dai Okamoto ◽  
Hiroshi Yano ◽  
Yuki Oshiro ◽  
Tomoaki Hatayama ◽  
Yukiharu Uraoka ◽  
...  
Keyword(s):  
Field Effect ◽  
High Performance ◽  
Room Temperature ◽  
Field Effect Transistors ◽  
Gate Oxide ◽  
Metal Oxide Semiconductor ◽  
Oxide Semiconductor ◽  
Interface Traps ◽  
Direct Oxidation ◽  
Mos Capacitors

Characteristics of metal–oxide–semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs) fabricated by direct oxidation of C-face 4H-SiC in NO were investigated. It was found that nitridation of the C-face 4H-SiC MOS interface generates near-interface traps (NITs) in the oxide. These traps capture channel mobile electrons and degrade the performance of MOSFETs. The NITs can be reduced by unloading the samples at room temperature after oxidation. It is important to reduce not only the interface states but also the NITs to fabricate high-performance C-face 4H-SiC MOSFETs with nitrided gate oxide.

Surface Treatment of 4H-SiC MOSFETs Prior to Al2O3 Deposition

2020 ◽  
Vol 1004 ◽  
pp. 541-546
Author(s):  
Muhammad Idzdihar Idris ◽  
Alton B. Horsfall
Keyword(s):  
Surface Treatment ◽  
Field Effect ◽  
High Performance ◽  
Interface State ◽  
State Density ◽  
Interface State Density ◽  
Surface Treatments ◽  
Flat Band ◽  
Field Effect Mobility ◽  
Mos Capacitors

The effect of surface treatments prior to the deposition of Al2O3 is performed on 4H-SiC MOS capacitors and MOSFETs. 40 nm of Al2O3 were deposited on 4H-SiC using atomic layer deposition (ALD) as a gate dielectric. Different surface treatments were used to investigate the capacitance-voltage and current-voltage characteristics on MOS capacitors and MOSFETs respectively, including the important parameters such as interface state density, flat band voltage, threshold voltage and field-effect mobility. Forming gas annealing and rapid oxidation processes were found to be effective in reducing the interface state density and results in high field-effect mobility with peak field-effect mobility of 130 cm2Vs-1. The experimental results obtained manifest that the surface treatment prior to Al2O3 deposition is critical to producing high performance of 4H-SiC MOSFETs.

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