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In this letter, it is demonstrated that 4H-SiC MOSFETs with borosilicate glass (BSG) as the gate dielectric result in significantly higher channel mobility than standard nitride oxide annealed devices, due to lower density of near-interfacial traps at the BSG/SiC interface. Using a thin Antimony-doped surface layer in conjunction with the BSG dielectric results in higher channel mobility at room temperature. The field-effect channel mobility of such devices is found to be 180 ${\rm {cm}}^{{2}}/{\text {V}}\cdot \text {s}$ at low transverse electric fields (close to threshold) and 94 ${\text {cm}}^{\text {2}}/{\text {V}}\cdot \text {s}$ at high fields (~2 MV/cm), which is about a factor of five higher than the state-of-the-art. This, along with a tunable threshold voltage, could make this approach very attractive for power MOSFET applications. However, the poor bias temperature instability of BSG is a big challenge for utilization of this dielectric.

An electroless nickel film contains 5-14% by weight of phosphorus. Because of the presence of such a high concentration of phosphorus, electroless nickel can be a useful and convenient source of phosphorus dopant in the fabrication of n-type ohmic contacts for SiC. This paper describes the successful deposition of a Ni:P layer on 4H-SiC through electroless nickel plating followed by a discussion of the results of surface science and electrical measurements. Specific contact resistivity on lightly-doped samples with carrier concentration of 2.5 ´ 1016 cm-3 has been found to be about 4.8 ´ 10-6 Ωcm2 without any need for ion implantation. This metallization technique is especially useful in broad area ohmic contact formation on the back of n-type SiC substrate.

The field of SiC electronics has progressed rapidly in recent years, but certain electronic properties remain poorly understood. For example, a consensus has not been reached as to the specific point defects which limit minority carrier recombination, and little is known about defects which limit generation lifetimes. This paper investigates generation lifetimes using the pulsed MOS capacitor technique and compares the results with defect densities, recombination lifetimes, and Schottky diode characteristics in the same material for the first time. Carrier generation lifetimes in 4H-SiC epilayers range from less than 1 ns to approximately 1 μs and depend strongly on measurement conditions and data interpretation. They are limited by dislocations only at densities higher than 106 cm-2.The only point defect that is theoretically capable of limiting generation lifetime to the levels currently observed in 4H-SiC is EH 6/7. However, this defect cannot account for the case where generation lifetimes are lower than recombination lifetimes in the same area. This is not seen in silicon and seems to be inconsistent with theory. Possible reasons for these perplexing results are discussed, and it is attempted to form a framework with which further understanding of the significance of carrier generation lifetime measurements in SiC can be achieved.

Samples for transmission line model (TLM) and Hall measurements were fabricated on (0001) 4H-SiC implanted with nitrogen at 1 × 1018 cm−3, 4 × 1018 cm−3, 1 × 1019 cm−3, 4 × 1019 cm−3, and 1 × 1020 cm−3. Following high-temperature activation, the activation percentage dropped from ~90% to ~20%, and the Hall mobility decreased from ~100 cm2/V · s to ~20 cm2/V · s as the implant concentration increased from 1 × 1018 cm−3 to 1 × 1020 cm−3. The specific contact resistance as a function of Hall concentration is compared with published data for Ni contacts to epitaxial layers. The specific contact resistance as a function of activation temperature was also studied for two fixed implant concentrations of 5 × 1018 cm−3 and 1 × 1020 cm−3.

Metal–oxide–semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs) fabricated on the carbon face of 4H-SiC were characterized following different postoxidation annealing methods used to passivate the oxide–semiconductor (O–S) interface. Of the various processes studied, sequential postoxidation annealing in NO followed by atomic hydrogen gave the lowest interface trap density (D it). Direct oxidation/passivation in NO yielded somewhat better I–V characteristics, though all passivation ambients produced approximately the same breakdown field strength. n-Channel MOSFETs showed high channel mobility at low field, which is likely caused by the presence of mobile ions at the O–S interface. Comparisons with the silicon face are presented for interface trap density, oxide breakdown field, and channel mobility. These comparisons suggest that the carbon face does not offer significant performance advantages.

High-temperature processing was used to improve the barrier properties of three sets of n-type 4H-SiC Schottky diodes fabricated with Ni Schottky contacts. We obtained an optimum average barrier height of 1.78 eV and an ideality factor of 1.09 using current–voltage measurements on diodes annealed in vacuum at 500°C for 24 h. Nonannealed contacts had an average barrier height of 1.48 eV and an ideality factor of 1.85. The Rutherford backscattering spectra of the Ni/SiC contacts revealed the formation of a nickel silicide at the interface, accompanied by a substantial reduction in oxygen following annealing.

The pulsed MOS-C (Metal Oxide Semiconductor-Capacitor) technique was used to measure generation lifetimes in 4H-SiC epitaxial wafers. The ratio of generation to recombination lifetime has been investigated to understand the dominant defect for generation lifetime. The EH6/7 defect level is considered to limit generation lifetime and field enhanced emission is proposed to explain extremely large variation of generation lifetime in a small area. Generation lifetime is limited by dislocations when they are above a threshold density of about 106cm-2. Generation lifetimes measured on 4 and 8 degree off-cut angle epi-substrates are very comparable.

Compared to silicon, there have been relatively few comparative studies of recombination and carrier lifetimes in SiC. For the first time, both generation and recombination carrier lifetimes are reported from the same areas in 20 m thick 4H SiC n-/n+ epi-wafer structures. The ratio of the generation to recombination lifetime is much different in SiC compared to Si. Activation energy calculated from SiC generation lifetimes shows that traps with energy levels near mid-gap dominate the generation lifetime. Comparison of both generation and recombination lifetimes and dislocation counts measured in the device area show no correlation in either case.

Thermal oxides on the Ga-face of low defect density bulk gallium nitride (GaN) were controllably produced under varying conditions and subsequently analyzed. The thermal oxidation was performed in a dry oxygen atmosphere at different temperatures and different oxidation times. Each oxide layer was identified as the monoclinic β-Ga2O3 by a θ–2θ X-ray diffraction (XRD) scan. Complementary Auger electron spectroscopy (AES) and high-resolution X-ray photoelectron spectroscopy (XPS) were also performed to study the chemical and electronic states of the oxide. The surfaces of the as-grown oxide and the GaN surfaces (after oxide removal) were studied using scanning electron microscopy (SEM). The roughness of both surfaces was found to increase with increasing oxidation temperature. Schottky diodes were fabricated on the GaN surfaces after oxide removal to further examine the surface quality. An excess reverse leakage current was found for Schottky diodes fabricated on GaN surfaces that were oxidized at 950 °C or 1000 °C, indicating possible surface decomposition at these two temperatures. The characteristics of wet and dry etching of the gallium oxide layer were also investigated. Finally, metal–oxide–semiconductor (MOS) capacitors were fabricated using thermally oxidized bulk GaN substrates. Current–voltage (I–V) measurements showed a low reverse current of 1.5 pA at −10 V. The oxide breakdown field was determined to be 0.65 MV/cm. Capacitance–voltage (C–V) measurements displayed a deep depletion feature, and the interface trap density near the conduction band was estimated to be in the low 1011 eV−1 cm−2 range.

A new method for precisely measuring low gate oxide currents by measuring the charge leaking through the oxide in a pulsed metal oxide semiconductor capacitor (MOS-C) is presented. Using basic equipment, it is possible to measure currents less than 10 fA/cm2 . The relevant theory is developed to use these capacitance-time data to extract an approximate leakage current and the effect on the extracted generation lifetime. The technique is simple and requires the same equipment used for pulsed MOS-C generation lifetime measurements. Experimental results are presented, which are consistent with theory.

The radiation tolerance of strained Si/SiGe n-MODFETs is investigated, using 10 keV X-rays, 63 MeV high energy protons, and 4 MeV low energy protons. The effects of radiation exposure on two major device design parameters (LSD and LG) in T-gate Si/SiGe n-MODFETs devices are examined. A strong dependence on source-drain spacing is observed for both the DC and RF characteristics. A drift-diffusion TCAD framework is used for 2-D device simulations. We believe that the low energy protons damage the SiGe/strained-Si/SiGe lattice, leading to partial strain relaxation. The conduction band-offset (CBO) of the strained SiGe/Si heterojunction is lowered leading to higher gate current leakage. The presence of radiation-induced bulk traps in the unrelaxed SiGe layers on the device behavior is also investigated.

We report on improved electrical properties and thermal stability of ZrB2 Schottky contacts deposited on n-type 4H-SiC at temperatures between 20°C and 800°C. The Schottky barrier heights (SBHs) determined by current-voltage measurements increased with deposition temperature, from 0.87 eV for contacts deposited at 20°C to 1.07 eV for those deposited at 600°C. The Rutherford backscattering spectroscopy (RBS) spectra of these contacts revealed a decrease in oxygen peak with an increase in the deposition temperature and showed no reaction at the ZrB2/SiC interface. These results indicate improved electrical and thermal properties of ZrB2/SiC Schottky contacts, making them attractive for high-temperature applications.

In this work, we have investigated the effect of Antimony counter-doping in channel region of 4H-SiC MOSFETs with moderately doped p-body, relevant for power applications. Using this process, improved sub-threshold slope and high channel mobility have been achieved in conjunction with high threshold voltage. Our results indicate that the improvement in transport is associated with Sb donors close to the surface, which have negligible effect on interface trap density.

Post-oxidation anneals that introduce nitrogen at the SiO2/4H-SiC interface have been most effective in reducing the large interface trap density near the 4H-SiC conduction band-edge for (0001) Si face 4H-SiC. Herein, we report the effect of nitridation on interfaces created on the (11 20) a-face and the (0001) C-face of 4H-SiC. Significant reductions in trap density (from >1013 cm-2 eV-1 to ~ 1012 cm-2 eV-1 at EC-E ~0.1 eV) were observed for these different interfaces, indicating the presence of substantial nitrogen susceptible defects for all crystal faces. Annealing nitridated interfaces in hydrogen results in a further reduction of trap density (from ~1012 cm-2 eV-1 to ~5 x 1011 cm-2 eV-1 at EC-E ~0.1 eV). Using sequential anneals in NO and H2, maximum field effect mobilities of ~55 cm-2 V-1s-1 and ~100 cm-2 V-1s-1 have been obtained for lateral MOSFETs fabricated on the (0001) and (11 20) faces, respectively. These electronic measurements have been correlated to the interface chemical composition.

Silicon has been the semiconductor of choice for microelectronics largely because of the unique properties of its native oxide (SiO2) and the Si/SiO2 interface. For high-temperature and/or high-power applications, however, one needs a semiconductor with a wider energy gap and higher thermal conductivity. Silicon carbide has the right properties and the same native oxide as Si. However, in the late 1990’s it was found that the SiC/SiO2 interface had high interface trap densities, resulting in poor electron mobilities. Annealing in hydrogen, which is key to the quality of Si/SiO2 interfaces, proved ineffective. This paper presents a synthesis of theoretical and experimental work by the authors in the last six years and parallel work in the literature. High-quality SiC/SiO2 interfaces were achieved by annealing in NO gas and monatomic H. The key elements that lead to highquality Si/SiO2 interfaces and low-quality SiC/SiO2 interfaces are identified and the role of N and H treatments is described. More specifically, optimal Si and SiC surfaces for oxidation are identified and the atomic-scale processes of oxidation and resulting interface defects are described. In the case of SiC, we conclude that excess carbon at the SiC/SiO2 interface leads to a bonded Si-C-O interlayer with a mix of fourfold- and threefold-coordinated C and Si atoms. The threefold coordinated atoms are responsible for the high interface trap density and can be eliminated either by H-passivation or replacement by N. Residual Si-Si bonds, which are partially passivated by H and N remain the main limitation. Perspectives for the future for both Si- and SiC-based MOSFETs are discussed.

SiC based field-effect devices are attractive for electronic and sensing applications above 250 °C. At these temperatures the reliability of the insulating dielectric in metal-oxidesemiconductor (MOS) structures becomes an important parameter in terms of long-term device performance. We report on the reliability of n-MOS SiC capacitors following thermal stress cycling in the 330 to 630 °C range. As the primary mode of oxide breakdown under these conditions is believed to be due to electron injection from the substrate, the gate leakage current was measured as a function of temperature. The gate dielectric was grown using dry oxidation with a post oxidation NO passivation anneal. For large area, 1 mm diameter, 6H-SiC capacitors we obtain current densities as low as 5nA/cm2 at 630 °C. In addition, gate leakage measurements from arrays of 300 to 1000 2m diameter devices fabricated on different 1cm2 6H-SiC substrates are presented. These are encouraging results for the long-term reliability of SiC field-effect sensors.

Low interface trap density and high channel mobility on nonpolar faces of 4H-SiC, such as the (11[2]0) a-face, are of fundamental importance in the understanding of SiC MOS devices. It is also critical for high-voltage trench power MOSFET development. We report new results on the passivation of the SiO2/a-face 4H-SiC interface using phosphorus, yielding field effect mobility of ~125 cm2/V · s. We also revisit the conventional NO passivation, for which a mobility of ~85 cm2/V · s was achieved on the a-face. These results not only establish new levels of mobility in SiC MOSFETS but also lead to further insights into factors currently limiting SiC inversion layer mobility.

Phosphorous from P2O5 is more effective than nitrogen for passivating the 4H-SiC/SiO2 interface. The peak value of the field-effect mobility for 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) after phosphorus passivation is approximately 80 cm2/V·s. However, P2O5 converts the SiO2 layer to phosphosilicate glass (PSG)-a polar material that introduces voltage instabilities which negate the benefits of lower interface trap density and higher mobility. We report a significant improvement in voltage stability with mobilities as high as 72 cm2/V·s for MOSFETs fabricated with a thin PSG gate layer ( ~ 10 nm) capped with a deposited oxide.

The radiation response of SiO 2 gate oxides grown on 4H-SiC to NO passivation is presented for the first time. The effects of gamma radiation on Q eff are similar for n-4H-SiC MOS capacitors both with and without NO passivation, but are different in sign (negative) compared to SiO 2 on Si. The variation in D it with total dose, however, is different for the passivated versus the unpassivated samples. Comparisons between Si SOI and 4H-SiC suggest that properly passivated SiC MOSFETs should have good radiation tolerance.

Alloys of aluminum and titanium have been successfully used to form low resistance ohmic contacts to p-type SiC. While the 90 wt.% Al alloy has been studied extensively, the literature does not reveal any work which indicates whether the 90/10 or any other alloy composition is the best alloy for use as an ohmic contact material to p-SiC. This work systematically looks at four different Al–Ti alloy compositions in an attempt to decide which alloy if any is superior as an ohmic contact material. The alloy compositions that were studied were chosen by examining the binary Al–Ti phase diagram and choosing specific phases prior to reaction with the SiC. It will be shown that only alloys which have some amount of a liquid phase present at the anneal temperature will form an ohmic contact to p-type SiC.

As the laminate substrate industry moves from hot air solder level (HASL) finishes, alternate plating finishes are being proposed such as immersion gold/electroless nickel, electroless palladium, and electroless silver. This paper presents results of an evaluation of the thermosonic gold ball wire bondability of electroless palladium. Two palladium thicknesses, with and without a nickel underlayer, were evaluated from two vendors. In each case, a thin gold passivation layer was deposited by immersion plating over the palladium. The initial evaluation criteria included bondability (number of missed bonds and flame off errors), wire pull strength, standard deviation, bond failure mode, and visual inspection. The bonding window was determined by independently varying force (four levels), power (four levels), and time (two levels). The stage temperature was maintained at 150/spl deg/C, compatible with BT laminate material. Different preconditioning environments such as a solder reflow cycle, high temperature storage (125/spl deg/C) and humidity storage (85%RH/85/spl deg/C) on initial bondability were also considered. Rutherford backscattering and Auger analysis were used to examine the surface finishes. The stability of the bonds was investigated by high temperature storage (125/spl deg/C) with periodic electrical resistance and pull strength testing.

Nitric oxide postoxidation anneal results in a significant decrease of defect state density (Dit) near the conduction bandedge of n-4H–SiC at the oxide/(1120) 4H–SiC interface. Comparison with measurements on the conventional (0001) Si-terminated face shows a similar interface state density following passivation. Medium energy ion scattering provides a quantitative measure of nitrogen incorporation at the SiO2/SiC interface.

The oxidation and diffusion of Molybdenum layer sputter-deposited on 2μm CVD diamond grown on silicon substrate has been studied. The Mo layer was protected by refractory metal silicide barrier layer. The samples were annealed in air ambient at 500°C over 30 hours. The oxidation of the samples was monitored with Rutherford Backscattering Spectroscopy (RBS). The effect of reactive sputtering of refractory silicide target in argon-nitrogen gas mixture (5% nitrogen by flow rate) on the barrier characteristics was investigated. The sheet resistivity of the barrier layer on SiC substrates as a function of annealing time in air at 500°C is reported. The surface structure and morphology of the refractory silicide films was determined with X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).

Results for measurements of interface state density and breakdown field strength are reported for deposited oxides on n 4H–SiC following passivation with nitric oxide. Low-temperature oxides deposited by plasma-enhanced chemical vapor deposition and high-temperature oxides deposited at 950 °C were investigated. Nitrogen passivation of deposited oxides on n 4H–SiC is found to produce interface state densities of 1–2×1012 cm−2 eV−1 at Ec−E=0.1 eV, regardless of variations in oxide deposition procedures that affect the residual interfacial carbon concentration. Breakdown field strengths were higher for passivated high-temperature oxides compared to passivated low-temperature oxides at room temperature and 290 °C. We suggest that additional oxide growth during the NO passivation is the reason for the observed interface state densities.

Thin films of CuInSe2 (CIS) and CuGaSe2 (CGS) were deposited on (100) Si substrates by RF magnetron sputtering using stoichiometric targets, at various substrate temperatures. Prior to film deposition, the Si substrates were cleaned using the RCA cleaning procedure and treated in a buffered oxide etch (BOE) solution. Deposited films were characterized using Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM) of cross-sectional samples and Hall measurements. Rutherford backscattering analysis indicated that the CIS films had a composition of Cu0.8In1.1Se1.9, whereas CGS films were Cu-poor and Ga-rich with a composition of Cu0.3Ga1.5Se1.5. Clean Cu-chalcopyrite/Si interfaces were obtained using BOE treated Si substrates. Transmission electron micrographs of cross-sectional samples indicated a polycrystalline film structure and that the native oxide on the Si substrate was eliminated. Energy dispersive X-ray spectroscopy (EDS) conducted in the TEM showed that contamination levels in the films were low. The Hall-mobility experiments performed the CIS film indicated that the material was of p-type conductivity with a carrier concentration of 9.6 x 1020/cm3 and a Hall mobility of 390 cm2V-1s-1.

Small bursts of inversion layer charge in 4H-SiC metal oxide semiconductor capacitors leak through the oxide layer leading to discontinuities during capacitance-time measurements. This behavior has been observed using non-equilibrium capacitance-time (C-t) and current-time (I-t) measurements, at room temperature and at 400degC.

The electrical and physical properties of silicon carbide (SiC) and its ability to form insulating SiO2 layers by thermal oxidation make it a promising material for high power, high-temperature, and high-frequency metal-oxide-semiconductor field effect transistors (MOSFETs). However, the development of 4H-SiC MOSFETs has been hindered by the high-density of interface states (Dit) at the SiO2/4H-SiC interface and a reduced electron mobility of

Recent work with polyhedral oligomeric silsesquioxanes (POSS) modified polymers has identified several enhanced characteristics in the hybrid material, including improved radiation and atomic oxygen durability in simulated space environment and extended duration space flight test experiments. Results are summarized for simulated radiation and oxidizing environment tests on POSS modified epoxy resins polyimide and DC93-500 silicon. Preliminary tests indicate that the addition of POSS into DC93-500 improves resistance to frosting due to oxidization of the surface. Additionally the hybrid material has less surface tack and self-adhesion than the stock material providing improved handling characteristics. Additional tests indicate that the hybrid material has the same radiation tolerance as the stock material when exposed to 2MeV protons. In addition to the DC93-500, a series of epoxy polymers of various composition and formulations have been screened to identify materials suitable for usage as a cover glass replacement material on single crystal or thin film solar cells. A summary of the effects of radiation and oxidizing environment on the transmittance and durability is presented.

The effects of 63 MeV proton irradiation on 90 nm strained silicon CMOS on insulator is examined for the first time. The devices show no observable degradation in DC performance up to an equivalent total dose of 600 krad(Si). The performance of the strained pFETs is identical to unstrained pFETs and demonstrates the immunity of strain to displacement damage. There is no significant enhancement observed in back channel leakage for the maximum dose. Passive exposure to 2 Mrad(Si) using 4 MeV protons doesn't induce any significant performance degradation.

In this paper, the problem of high interface traps at the SiO2/SiC interface is introduced and their possible cause and physical nature are discussed. Different state-of-the-art approaches to chemically modify the interface for 'passivating' such electrically active traps is reviewed. In particular, the significant improvement of the interface by nitridation via nitric oxide post-oxidation annealing is highlighted. Correlations between electrical and physical measurements, which reveal the role of nitrogen in the passivation process, are discussed. Results presented for oxides grown on the conventional (0001) Si-face as well as other 'alternate' crystal faces. Recent work on the use of hydrogenation to obtain additional passivation for nitridated interfaces is also introduced. Finally, the major unresolved issues and opportunities for further research and development on this subject are indicated

The interface passivation process based on post-oxidation, high temperature anneals in nitric oxide (NO) is well established for SiO2 on (0001) 4H-SiC. The NO process results in an order of magnitude or more reduction in the interface state density near the 4H conduction band edge. However, trap densities are still high compared to those measured for Si / SiO2 passivated with post-oxidation anneals in hydrogen. Herein, we report the results of studies for 4H-SiC / SiO2 undertaken to determine the effects of additional passivation anneals in hydrogen when these anneals are carried out following a standard NO anneal. After NO passivation and Pt deposition to form gate contacts, post-metallization anneals in hydrogen further reduced the trap density from approximately 1.5 × 1012 cm−2eV−1 to about 6 × 1011 cm−2eV−1 at a trap energy of 0.1 eV below the band edge for dry thermal oxides on both (0001) and (11–20) 4H-SiC.

Silicon carbide (SiC) is an excellent semiconductor for the fabrication of high power and high temperature electronic devices. SiC pn junctions are critical components of SiC high power devices and circuits. However, the high electric field behavior of SiC p-n junction structures is not well characterized. The study of the high field breakdown mechanisms of SiC p-n junction plays an important role in determining the proper design of SiC high power p-n junction-based devices. We have determined the high field breakdown behaviors of several types of 4H-SiC epitaxial p-n junction diodes of different design. In our efforts to increase the breakdown voltage, we have found that oxide passivation did not substantially affect the breakdown voltage but edge termination using argon ion implantation is effective in improving the breakdown voltage of SiC-p-n junction diodes.

Two high temperature ohmic contacts to epitaxial p-type SiC using Ti and CrB/sub 2/ will be discussed. Fabrication techniques are described along with the results of electrical and physical characterization of these contacts. Transmission line measurements show that these contacts have specific contact resistances almost as low as contacts using Al-Ti; however these contacts exhibit much more reproducibility and are more stable at elevated temperatures. Physical analysis will also show that the surface morphology of these contacts is superior to conventional Al-Ti ohmic contacts. The Ti contact is well suited for use in device fabrication processes since it requires a relatively low temperature (800/spl deg/C) anneal for only one minute to form the ohmic contact. The CrB/sub 2/ on the other hand requires an 1100/spl deg/C anneal for 30 minutes to form the ohmic contact, although shorter annealing times yield linear contacts with much higher contact resistances. In addition, Ti ohmic contacts to implanted p-type material will be discussed. The implanted SiC used in this work consists of Al only and Al plus C co-implanted material. The specific contact resistances obtained to implanted SiC are found to vary considerably depending on the type of implant and the post activation anneal process that is used.

Aluminum nitride (AlN) is a potential gate insulator material for 6H-SiC metal-insulator-semiconductor (MIS) devices for high temperature and high power applications. A critical requirement for a viable gate insulator material is that the insulator/semiconductor interface must have a very low interface state density, low insulator fixed charge density, as well as a low density of interfacial trapping centers. Our capacitance-voltage (CV) measurements have shown that it is possible to obtain an AlN/6H-SiC interface with such characteristics. Although CV measurements done at 573 K have shown evidence of the activation of deeper interfacial charged centers, they still reveal the presence of a low number of interface states and low insulator charge density. The disadvantage of this material system is the high leakage current density. However, by using a stacked AlN structure, we have found that it is possible to obtain MIS structures that are able to sustain breakdown fields close to the theoretical values. The possible use of a very thin AlN layer to enhance the characteristics of a Au-6H-SiC Schottky diode will also be discussed.

The current vs voltage characteristics of 4H-SiC MOS capacitors under deep depletion are obtained by a fast ramp response technique so as to obtain the maximum field that can be applied to the MOS structure without the failure of either the semiconductor or the oxide layer. The experiments on n-type 4H SiC wafers having a 5 μm thick epilayer of 1015 – 1016 cm−3 doping concentration and an oxide layer 1200Å – 1500Å thick, indicate the significant influence of the oxide quality and defects in the semiconductor on the nature of the current response during accumulation and deep depletion measurements. The effect of the conductivity of the oxide layer is reflected clearly in the current response, even though classical C-V measurements do not indicate any abnormality. Apart from obtaining the maximum breakdown fields of the semiconductor and the oxide, the fast-ramp response technique provides useful information about the generation processes associated with defects in the MOS structure.

We report specific contact resistances measured at elevated temperatures for Ni ohmic contacts to 6H‐SiC. The specific contact resistances were measured with the linear transmission line method at both room temperature and at 773 K and yielded values

The electrical properties and thermal stability of ZrB2 Schottky contacts deposited on n-type GaN have been studied. As-deposited contacts had a barrier height of 0.80eV, which decreased to 0.7eV after annealing at 300°C, and to 0.6eV after additional annealing at 400°C in nitrogen for 20min. However, the barrier height remained at about 0.6eV even when the diodes were annealed at 600°C for 20min. The Rutherford backscattering spectra of annealed contacts showed no reaction at the ZrB2∕GaN interface. These results make ZrB2∕GaN Schottky contacts attractive for high temperature device applications.

Interface trap passivation at the SiO2∕carbon-terminated (0001¯) face of 4H-SiC utilizing nitridation and hydrogenation has been evaluated. The SiO2∕SiC interface, created by dry thermal oxidation on the C face, shows appreciably higher interface state density near the conduction band compared to the (0001) Si face. A postoxidation anneal in nitric oxide followed by a postmetallization anneal in hydrogen results in dramatic reduction of the trap density by over an order of magnitude near the conduction band. The electrical measurements have been correlated with the interfacial chemistry.