AIN(Er) doped with Er during Metal Organic Molecular Beam Epitaxy has been plasma hydrogenated in-situ at 200–250°C using an Electron Cyclotron Resonance source. By isotopic substitution of 2H for 1H, we have found from Secondary Ion Mass Spectrometry profiling that a 30 min hydrogenation treatment can incorporate ˜2×1019cm−3 deuterium atoms to depths ≥1μm. The intensity of the 1.54μm Er3+ luminescence is increased by a factor of ˜5 by the 200°C hydrogenation, and this effect is thermally stable to 300°C, indicating a binding energy of >1.5eV for hydrogen at defects in the AIN. These defects would normally either be recombination centers or provide an alternative de-excitation path for the Er. We have previously found that AIN provides the best resistance to thermal quenching of Er luminescence of any semiconductor due to its wide bandgap. Together, these results suggest that AIN(Er) may be a promising material for optical control of devices such as light-triggered SiC or GaN thyristors for power switching applications, where a fiber-transmitted signal from temperaturetolerant material is necessary in controlling power distribution grids. Hydrogen does not leave the AIN until ˜800°C and presumably forms an intermediate state such as H2 or larger clusters prior to evolution from the surface, and again this stability is among the best for any semiconductor.

A number of different plasma chemistries, including NF3/O2, SF6/O2 , SF6/Ar, ICI, IBr, Cl2/Ar, BCl3/Ar and CH4/H2/Ar, have been investigated for dry etching of 6H and 3C-SiC in a Inductively Coupled Plasma tool. Rates above 2,000 Å·cm−1 are found with fluorine-based chemistries at high ion currents. Surprisingly, Cl2-based etching does not provide high rates, even though the potential etch products (SiCl4 and CCl4 ) are volatile. Photoresist masks have poor selectivity over SiC in F2 - based plasmas under normal conditions, and ITO or Ni are preferred.

For power devices the use of silicon epilayer on CZ substrate is a solution to make devices with a low oxygen concentration in the active zone. Oxygen is probably one of the most important residual impurities in silicon samples. Usualy the determination of the interstitial oxygen is done by Fourier Transform Infra Red spectroscopy (FTIR). In this work we have determined oxygen by Charged Particle Activation Analysis (CPAA). The main difference between these two techniques is that CPAA gives the total oxygen concentration whereas FTIR gives interstitial oxygen.

We have determined the oxygen in 200μm thick silicon epilayer and studied its behavior during thermal treatments. Oxygen concentration is found in the range of 1015/cm3 just after the epitaxial process. After thermal treatment the concentration in the epilayer rose to several 1016/cm3 to 1017/cm3, depending on the treatment. A comparison with FTIR experiment is done and the amount of oxygen precipitate is determined.

Mass spectrometry of the plasma effluent during Reactive Ion Beam Etching (RIBE) of GaAs using an Inductively Coupled Plasma (ICP) source and a Cl2/Ar gas chemistry shows that AsCl3, AsCl2 and AsCl are all detected as etch products for As, while GaCl2 is the main signal detected for the Ga products. The variation in selective ion currents for the various etch products has been examined as a function of chuck temperature (30–100°C), percentage Cl2 in the gas flow, beam current (60–180 mA) and beam voltage (200–800 V). The results are consistent with AsCl3 and GaCl3 being the main etch product species under our conditions, with fragmentation being responsible for the observed mass spectra.

Deep level Transient Spectroscopy (DLTS), Electron Beam Induced Current (EBIC), EBIC Diffusion Length Mapping (EBIC-DLM) and contactless Photoconductive Decay (PCD) were used to characterize both bulk substrates and epitaxially grown Silicon Carbide films. Traps as deep as 0.93 eV were observed via DLTS. These traps may play a role in the persistent photoconductivity effect. EBIC reveals the electrical activity of the well known triangular defects. However, only some of these defects display electrical activity consistent with that of 3C-SiC inclusions, others do not. Additionally, not all defects identified in the EBIC images are observable in the topographic SEM image, possibly indicating a new, yet unidentified defect. EBIC revealed the electrical activity of defects including micro-pipes, dislocations (or possibly growth step edge decoration), surface polish damage, and bulk defects. Diffusion length maps of SiC indicate wide variations in diffusion length on both microscopic and macroscopic scales. EBIC-DLMindicatedepitaxial 4H SiC resulted in diffusion lengths from 0.1 to 3 μm, while bulk values were less than 0.07 μm. PCD measurements indicate tens of nanosecond to microsecond variations in lifetime. Lifetime verses injection level variations are observed and explained on the basis of trap energy. The injection level dependence of lifetime was observed at various nitrogen doping concentrations. Finally, electron beam annealing is found to dramatically improve the minority carrier lifetime in epitaxial SiC.

The local bonding environments in silicon oxycarbide thin films with different amounts of carbon were analyzed using the complementary optical techniques of Fourier transform infrared (FTIR) and Raman spectroscopies. Film formation was accomplished by low-temperature (250°C), plasma-enhanced CVD using SiH4, CH4 and O2 as the source gases. Control samples were also deposited using only SiH4 and CH4, and SiH4 and O2 source gases. The films were then subjected to rapid thermal annealing at 800, 900 and 1100 °C for 90 seconds. Results showed that carbon incorporation into the oxide hinders stoichiometric SiO2 formation upon annealing at 800 and 900 °C. Annealing at 1100 °C produced films which showed stoichiometric SiO2 formation. Phase separation into nano-crystalline silicon (<5 nm) and a mixture of amorphous silicon carbide and silicon oxide was also observed upon annealing, with crystallite size decreasing as the carbon content of the films was increased.

By virtue of its excellent electronic properties, diamond may become an important material for high temperature, high speed, high power and high compact electronic devices. However, most of these devices, single crystal or epitaxial films are required. Thus, for obvious reason, large-area heteroepitaxial diamond films are desired. Silicon is the most important material severed as a substrate for diamond heteroepitaxy. However, diamond can hardly be grown on mirror-polished Si, with nucleation density being only about 104 cm−2. Although scratching Si substrate could enhance greatly the nucleation density, it destroyed seriously the periodic structure of the Si surface. Thus diamond film grown on such a substrate will be randomly oriented polycrystallites. In order to overcome this difficulty, several methods have been developed, including (1) bias enhanced nucleation; (2) electron emission enhanced nucleation; (3) nucleation enhanced by slight surface modification; and (4) very low pressure ( 0.1 torr ) nucleation. We will introduce the second, third, and fourth methods, which were developed in our laboratory recently. Special attention will be paid to the relation between heteroepitaxy and high density nucleation. The incubation time for diamond nucleation is a critical parameter for high density nucleation and heteroepitaxy.

Real time in-situ laser reflectometry was used to investigate changes in surface morphology observed during the nucleation of oriented diamond on Ni in a hot filament chemical vapor deposition reactor. Characteristic features observed in the intensities of reflected and scattered light were interpreted by comparison with scanning electron micrographs of the diamond seeded substrates quenched at sequential stages of the process. Based on this analysis, a process was developed in which the scattered light signal was used as a steering parameter. Using this process, oriented nucleation and growth of diamond on Ni can be repeatedly achieved. For the purpose of both countering the loss of carbon atoms and to maximize the density of oriented diamond, different concentrations of methane were added during the high temperature annealing stage to find the optimized conditions. It was found that 0.5% methane in the gas phase produced the best degree of orientation and uniformity. Substrates nucleated at these conditions were grown out into coalesced, 30 μm thick films. Both, (100) and (111) oriented films showed a high degree of orientation. Raman spectra obtained from each orientation showed an intense and narrow diamond signature peak with negligible sp2 carbon or background luminescence.

Open-tube Ga diffusion into a SiO2/Si structure was used for fabrication of the high speed thyristor. The advantages of open-tube Ga diffusion are as follows; it is easier to operate and easier to control the profile of the Ga concentration during processing, a clean surface, which is free from alloy spots can be obtained, this technique ensures to improve the on-state characteristics and dynamic characteristics.

Wide applications of silicon carbide (SiC) films in microelectronics devices make especially important predictions of the doping profiles during and/or after thermal treatment. A macroscopic kinetic model of enhanced diffusion of aluminum in SiC films during ion bombardment at high temperatures has been considered. The set of equations describing the kinetic model takes into account generation Vc and Csi vacancies during bombardment, migration of mobile species (Al) toward the surface and reactions of Al atoms with Vc and Vsi vacancies, as well as Al evolution from the film. The calculations were carried out for the flux of Al ions with energy 40 keV and current density 20 μA/cm2 to a dose 2 1016 cm−2 at 1800° C. The calculations have shown that the Al content in SiC at these condition does not exceed 40%. The calculation profile of Al is in a good agreement with experimental data [1].

The interaction of cesium atoms with graphitized 4H-SiC(0001) surfaces was investigated by use of Auger electron, ultraviolet photoemission and high-resolution electron energy-loss spectroscopy (HREELS) as well as work function measurements with a Kelvin probe. The samples were annealed at temperatures well above 1300 K resulting in a formation of about two graphite layers on top of the SiC substrates. The corresponding low-energy electron diffraction image shows a () pattern. Cs deposition on graphitized SiC occurs in two subsequent stages. First, even small amounts of evaporated Cs lead to a spontaneous decrease in work function by 1.8 eV. The work function stays constant after further evaporation corresponding to an intercalation of Cs into the graphite overlayer. In the second stage Cs atoms are adsorbed on top of the Cs-intercalated compound resulting in a further decrease of work function. The graphite layer is effectively metallized by Cs evaporation. This is confirmed by a Fermi edge which is observed in the photoemission spectra even after the smallest dose applied. Moreover, the excitation of optical Fuchs-Kliewer phonons in SiC by HREELS is significantly quenched by the metallic overlayer and the electron energy-loss spectra exhibit features which are typical for thin homogeneous metal layers on surfaces of heteropolar semiconductors.

We have investigated the influence of TiN growth temperature on the contact resistance in TiN/SiC and TiN/GaN heterostructures. Epitaxial TiN layers grown at temperatures above 600°C formed low resistance contacts to n-type 6H-SiC and GaN of 1.1× 10−3 Ωcm2 and 7.9 ×10−5 Ωcm2, respectively. Structural and electrical characterization of TiN thin films is discussed.

MicroRaman spectroscopy is used for characterizing defects in large SiC crystals with micrometer spatial resolution. The ability to identify microscopic inclusions of polytypes different than the crystal matrix is demonstrated; silicon and carbon inclusions and disorder effects are found in micropipes. A study of the Longitudinal Optic Phonon Plasmon Coupled (LOPC) Raman modes allowed to obtain local fluctuations of the net donor concentration, ND-NA, and the electron mobility around defects, which allowed impurity gettering effects to be observed.

Silicon-carbon films have been grown by reactive hydrogen magnetron sputtering at a substrate temperature of 730°C, with different values of carbon-to-silicon sputtered area ratio, rc. The layers were investigated by infrared spectroscopy, Raman scattering, x-ray photoelectron spectroscopy and optical absorption. For rc below 30%, almost only Si nanocrystallites were formed with a few fraction of amorphous SiC, whereas for rc exceeding 30%, a drastic change was noticed, leading to the achievement of SiC crystals in the layers. These latter were found of near-stoichiometric composition with an atomic ratio C/Si ˜1.04. The results suggest that the excess C is of graphitic-like configuration being likely located in the intergrain regions, in addition to some silicon-oxygen bonds. These features are accompanied by an abrupt widening of the band gap in the transition region that is consistent with the formation of SiC nanocrystals. The large value measured for the band gap (≥3 eV) is thought to be due to more than one origin, such as size effect of SiC, Si-O bonds and possible presence of different SiC polytypes.

The development of low resistance ohmic metallizations to p-type 6H-SiC using a novel approach of focused ion beam (FIB) surface-modification and ex-situ epitaxial pulsed laser deposition (PLD) of TiN and Pt without further annealing, is reported. The FIB(Ga) surfacemodification and ex-situ epitaxial TiN and Pt PLD metallizations showed a significant reduction in contact resistance with surface-modification, reaching a minimum contact resistance value of 4.4×10−5 Ohm cm2 for the TiN system at an ion dose of 5.0×1016 ions/cm 2 and energy of 20 KeV. This contact resistance value is one of the lowest values reported to date. The Pt system showed increased contact resistance values as compared with the TiN, and reached minimum values for lower ion doses. The contact resistance values reported here are comparable to or lower than those reported for conventionally deposited and annealed contacts to p-type SiC.

The surface and interface properties of a Pd0.9Cr0.1/SiC Schottky diode gas sensor both before and after annealing are investigated using Auger electron spectroscopy (AES), scanning electron spectroscopy (SEM), and energy dispersive spectroscopy (EDS). At room temperature the alloy reacted with SiC and formed PdxSi only in a very narrow interfacial region. After annealing for 250 hours at 425 °C, the surface of Schottky contact area has much less silicon and carbon contamination than that found on the surface of an annealed Pd/SiC structure. PdxSi formed at a broadened interface after annealing, but a significant layer of alloy film is still free of silicon and carbon. The chromium concentration with respect to palladium is quite uniform down to deep interface region. A stable catalytic surface and a clean layer of Pd0.9Cr0.1 film are likely responsible for significantly improved device sensitivity.

Wet chemical etching of GaN, InN, AIN, InAlN and InGaN was investigated in various acid and base solutions at temperatures up to 75°C. Only KOH-based solutions were found to etch AIN and InAlN. No etchants were found for the other nitrides, emphasizing their extreme lack of chemical reactivity. The native oxide on most of the nitrides could be removed in potassium tetraborate at 75°C, or HCl/H2O at 25°C.

As the gate dimensions of FET's continue to shrink, the gate resistance increases. This increased gate resistance is undesirable for power applications. In order to reduce this problem short gate length features are covered with a larger length feature to reduce the gate resistance (T-gate)1. Generally this is done using bi-layer PMMA and E-beam writing for the upper and lower features, but this technique is very expensive and time consuming2,3. It is desirable to find a technique using conventional photoresist that would replace e-beam to produce T-gates.

We demonstrate a novel technique that utilizes conventional photoresist and optical stepper to create T-gate features4. The bottom feature is exposed and developed creating the lower part of the T. A short exposure of the photoresist pattern to an argon plasma hardens the resist just enough to allow a second layer to be put on without mixing of the two layers. This second layer is then exposed and developed forming the T. Plasma exposure allows us to create the second resist layer pattern without distorting or changing the bottom layer pattern. This technique is very robust, fast and much cheaper than e-beam technology.

Cubic SiC films have been grown on Si(001) and Si(111) substrates at temperatures between 600 °C and 900 °C with a single supersonic molecular beam source. Methylsilane (H3SiCH3) was used as the sole precursor with hydrogen and nitrogen as seeding gases. Optical reflectance was used to monitor in situ growth rate and macroscopic roughness. The growth rate of SiC was found to depend strongly on substrate orientation, methylsilane kinetic energy, and growth temperature. Growth rates were 1.5 to 2 times greater on Si(111) than on Si(001). The maximum growth rates achieved were 0.63 μm/hr on Si(111) and 0.375μm/hr on Si(001). Transmission electron diffraction (TED) and x-ray diffraction (XRD) were used for structural characterization. In-plane azimuthal (ø-) scans show that films on Si(001) have the correct 4-fold symmetry and that films on Si(111) have a 6-fold symmetry. The 6-fold symmetry indicates that stacking has occurred in two different sequences and double positioning boundaries have been formed. The minimum rocking curve width for SiC on Si(001) and Si(111) is 1.2°. Fourier Transform Infrared (FTIR) absorption was performed to discern the chemical bonding. Cross Sectional Transmission Electron Microscopy (XTEM) was used to image the SiC/Si interface.

It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector > 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = Ic with no hollow core) in densities on the order of thousands per cm2, nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage (I-V) characteristics of 4H-SiC p+n diodes. First, Synchrotron White Beam X-ray Topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p+n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast devices that contained at least one elementary screw dislocation exhibited a 5% to 35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.