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.

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.

Systematic Investigation of 4H-SiC Trench Properties Dependence on Channel Concentration, Crystallographic Plane, and MOS Interface Treatment

2016 ◽  
Vol 858 ◽  
pp. 639-642 ◽  
Author(s):  
Hidenori Kitai ◽  
Tomoaki Hatayama ◽  
Hideto Tamaso ◽  
Shinaya Kyogoku ◽  
Takeyoshi Masuda ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Epitaxial Growth ◽  
Threshold Voltage ◽  
Field Effect ◽  
Systematic Investigation ◽  
Crystallographic Plane ◽  
Field Effect Mobility ◽  
Channel Mobility ◽  
P Type ◽  
Interface Treatment

We have systematically investigated the trench properties of 4H-SiC for p-type channel doping level formed by epitaxial growth, crystallographic plane, and MOS interface treatment. Our results show that the channel mobilities on the (1-100), (11-20), (-1100), and (-1-120) planes gradually decreased in the range from 1 × 1016 to 1 × 1017 cm-3 as the epitaxial channel concentration increased. An inevitable tradeoff existed between channel mobility (field-effect mobility, µFE) and threshold voltage (Vth) in trench MOSFETs. Furthermore, the maximum µFE at a channel concentration of 1 × 1017 cm-3 was 95 cm2·V-1·s-1 on the (11-20) plane with wet + hydrogen (H2) annealing, 83 cm2·V-1·s-1 on the (1-100) plane with wet + H2 annealing and 57 cm2·V-1·s-1 on the (1-100) plane with nitric oxide annealing.

Process Optimisation for 4H-SiC MOSFET Applications

2006 ◽  
Vol 527-529 ◽  
pp. 1051-1054 ◽  
Author(s):  
Caroline Blanc ◽  
Dominique Tournier ◽  
Phillippe Godignon ◽  
D.J. Brink ◽  
Véronique Soulière ◽  
...  
Keyword(s):  
Field Effect ◽  
Oxidation Process ◽  
Gate Oxide ◽  
Process Optimisation ◽  
Field Effect Mobility ◽  
Oxide Formation ◽  
Step Procedure ◽  
P Type ◽  
Peak Value ◽  
Gas Precursor

We report on 4H-SiC MOSFET devices implemented on p-type <11-20>-oriented epitaxial layers, using a two-step procedure for gate oxide formation. First is a thin, dry, thermal SiO2 layer grown at 1050°C for 1 hour. Next, is a thick (50 nm) layer of complementary oxide deposited by PECVD using TEOS as gas precursor. With respect to the standard thermal oxidation process, this results in much improvement of the field effect mobility. For the best samples, we find a peak value in the range of 330 cm2/Vs while, on the full wafer, an average mobility of about 160 cm2/Vs is found. Up to now, this is one of the best results ever reported for 4H-SiC MOSFETs.

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.

Improved Performance p-type Polymer (P3HT) / n-type Nanotubes (WS2) Electrolyte Gated Thin-Film Transistor

MRS Advances ◽  
2018 ◽  
Vol 3 (27) ◽  
pp. 1525-1533 ◽  
Author(s):  
Eleonora Macchia ◽  
Alla Zak ◽  
Rosaria Anna Picca ◽  
Kyriaki Manoli ◽  
Cinzia Di Franco ◽  
...  
Keyword(s):  
Thin Film ◽  
Threshold Voltage ◽  
Field Effect ◽  
Thin Film Transistor ◽  
Fold Increase ◽  
Field Effect Mobility ◽  
Figures Of Merit ◽  
Electronic Channel ◽  
Improved Performance ◽  
P Type

ABSTRACTThis work decribes the enhancement of the electrical figures of merit of an Electrolyte Gated Thin-Film Transistor (EG-TFT) comprising a nanocomposite of n-type tungsten disulfide (WS2) nanotubes (NTs) dispersed in a regio-regular p-type poly(3-hexylthiophene-2,5-diyl) (P3HT) polymeric matrix. P3HT/WS2 nanocomposites loaded with different concentrations of NTs, serving as EG-TFTs electronic channel materials have been studied and the formulation has been optimized. The resulting EG-TFTs figures of merit (field-effect mobility, threshold voltage and on-off ratio) are compared with those of the device comprising a bare P3HT semiconducting layer. The optimized P3HT/WS2 nanocomposite, comprising a 60% by weight of NTs, results in an improvement of all the elicited figures of merit with a striking ten-fold increase in the field-effect mobility and the on/off ratio along with a sizable enhancement of the in-water operational stability of the device.

Fabrication of 4H-SiC p-Channel MOSFET with High Channel Mobility

2006 ◽  
Vol 527-529 ◽  
pp. 1301-1304
Author(s):  
Mitsuo Okamoto ◽  
Mieko Tanaka ◽  
Tsutomu Yatsuo ◽  
Kenji Fukuda
Keyword(s):  
Valence Band ◽  
Oxidation Process ◽  
Gate Oxide ◽  
Interface States ◽  
Wet Oxidation ◽  
Mos Capacitors ◽  
Channel Mobility ◽  
Dry Oxidation ◽  
Low Threshold ◽  
P Type

We have fabricated inversion-type p-channel MOSFETs on 4H-SiC substrates. In this paper, influences of gate oxidation process on the properties of p-channel MOSFETs were investigated. The gate oxide was formed under these three conditions: (i) dry oxidation, (ii) dry oxidation following wet re-oxidation, and (iii) wet oxidation. The C-V measurements of p-type 4H-SiC MOS capacitors revealed that wet oxidation process reduced the interface states near the valence band. The p-channel MOSFET with low interface states near the valence band indicated low threshold voltage (Vth), high field effect channel mobility (μFE) and low subthreshold swing (S). We obtained 4H-SiC p-channel MOSFET with high μFE of 15.6cm2/Vs by using wet oxidation as gate oxidation process.

Effects of N2O Anneal on Channel Mobility of 4H-SiC MOSFET and Gate Oxide Reliability

2005 ◽  
Vol 483-485 ◽  
pp. 697-700 ◽  
Author(s):  
Keiko Fujihira ◽  
Yoichiro Tarui ◽  
Kenichi Ohtsuka ◽  
Masayuki Imaizumi ◽  
Tetsuya Takami
Keyword(s):  
Field Effect ◽  
Gate Oxide ◽  
Field Effect Mobility ◽  
Channel Mobility ◽  
Oxide Reliability ◽  
Anneal Temperature

The effect of N2O anneal on channel mobility of inversion-type 4H-SiC n-channel MOSFET has been systematically investigated. It is found that the mobility increases with increasing anneal temperature from 900 to 1150°C. The highest field effect mobility of 30 cm2/Vs is achieved by 1150°C anneal for 3 h, which is about 20 times higher than that for non-annealed MOSFET. In order to investigate the oxide reliability, TDDB measurement has been performed on SiO2 grown on n-type 4H-SiC. The oxide lifetime is found to be drastically improved by N2O anneal.

Field Effect Mobility in n-Channel Si Face 4H-SiC MOSFET with Gate Oxide Grown on Aluminium Ion-Implanted Material

2005 ◽  
Vol 483-485 ◽  
pp. 833-836 ◽  
Author(s):  
G. Gudjónsson ◽  
H.Ö. Ólafsson ◽  
Fredrik Allerstam ◽  
Per Åke Nilsson ◽  
Einar Ö. Sveinbjörnsson ◽  
...  
Keyword(s):  
Field Effect ◽  
Functional Relationship ◽  
Gate Oxide ◽  
Aluminum Concentration ◽  
Field Effect Mobility ◽  
P Type ◽  
Channel Region ◽  
Mobility Reduction ◽  
Peak Field ◽  
Ion Implanted

We report investigations of Si face 4H-SiC MOSFETs with aluminum ion implanted gate channels. High quality SiO2/SiC interface is obtained both when the gate oxide is grown on p-type epitaxial material and when grown on ion implanted regions. A peak field effect mobility of 170 cm2/Vs is extracted from transistors with epitaxially grown channel region of doping 5x1015 cm-3. Transistors with implanted gate channels with aluminum concentration of 1x1017 cm-3 exhibit peak field effect mobility of 108 cm2/Vs, while the mobility is 62 cm2/Vs for aluminum concentration of 5x1017 cm-3. The mobility reduction with increasing acceptor density follows the same functional relationship as in n-channel Si MOSFETs.

Investigation of Intrinsic Electrical Characteristics and Contact Effects in p-Type Tin Monoxide Thin-Film Transistors Using Gated-Four-Probe Measurements

2015 ◽  
Vol 15 (10) ◽  
pp. 7582-7585 ◽  
Author(s):  
Young-Joon Han ◽  
Yong-Jin Choi ◽  
Hoon Jeong ◽  
Hyuck-In Kwon
Keyword(s):  
Field Effect ◽  
Electrode Materials ◽  
Electronic Energy ◽  
Electrical Performance ◽  
Electrical Characteristics ◽  
Field Effect Mobility ◽  
Short Channel ◽  
Oxide Tft ◽  
Parasitic Resistance ◽  
P Type

We investigate the intrinsic electrical characteristics and source/drain parasitic resistance in p-type SnO TFTs fabricated using Ni electrodes based on the gated-four-probe method. Because of the relatively high work function and inexpensive price, Ni has been most frequently used as the source/drain electrode materials in p-type SnO TFTs. However, our experimental data shows that the width normalized parasitic resistances of SnO TFT with Ni electrodes are around one to three orders of magnitude higher than those in the representative n-type oxide TFT, amorphous indium– gallium–zinc oxide TFT, and are comparable with those in amorphous silicon TFTs with Mo electrodes. This result implies that the electrical performance of the short channel SnO TFT can be dominated by the source/drain parasitic resistances. The intrinsic field-effect mobility extracted without being influenced by source/drain parasitic resistance was ∼2.0 cm2/Vs, which is around twice the extrinsic field-effect mobility obtained from the conventional transconductance method. The large contact resistance is believed to be mainly caused from the heterogeneous electronic energy-level mismatch between the SnO and Ni electrodes.

Investigation of Degradation of Inversion Channel Mobility of SiC MOSFET due to the Increase of Channel Doping

2005 ◽  
Vol 483-485 ◽  
pp. 829-832 ◽  
Author(s):  
Tetsuo Hatakeyama ◽  
Takatoshi Watanabe ◽  
Junji Senzaki ◽  
Makoto Kato ◽  
Kenji Fukuda ◽  
...  
Keyword(s):  
Hall Mobility ◽  
Carrier Density ◽  
Field Effect ◽  
Doping Concentration ◽  
Free Carrier ◽  
Hall Voltage ◽  
Field Effect Mobility ◽  
Channel Mobility ◽  
Free Carrier Density ◽  
Inversion Channel

This paper reports on the degradation of inversion channel mobility of SiC MOSFET caused by the increase of channel doping. SiC MOSFETs were fabricated on three wafers, the doping concentrations of the epitaxial layer of which were 16 10 2× cm-3 (sample A), 17 10 2× cm-3 (sample B) and 17 10 4× cm-3 (sample C). The field effect mobility sharply decreases as the doping concentration increases. Hall mobility measurements have been done to investigate the degradation of the mobility due to doping. The measurement of sample A shows that, as a consequence of the decrease of the free carrier density due to MOS interface traps, the Hall mobility is as much as a factor of ten higher than the field effect mobility. In contrast, in regard to the measurement of sample B and sample C, we encountered unstable Hall voltage and could not obtain reproducible results. This implies that such high-density traps are generated that a channel disappears in the higher-doping samples.

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