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Boron related photoluminescence (PL) and capacitance transient spectroscopy (DLTS and MCTS) peaks have been investigated around SIMS craters. Enhancement of boron and hydrogen related PL was observed in the vicinity of the crater, whereas the concentration of electrically active boron as measured by MCTS has decreased considerably. Comparison of the boron MCTS peak behavior after electron and proton irradiation is presented. Possible defect models based on the obtained results are discussed.

The hydrogen depth distribution in 4H-SiC after epitaxial growth at 1600 degreesC has been studied in detail with secondary ion mass spectrometry. Both H-1 and H-2 have been employed as carrier gas to trace the origin of the incorporated hydrogen. In particular the substrate as a prospective hydrogen source has been considered. After growth H-2 is detected throughout the whole substrate (similar to400 mum) and a considerable quantity remains after annealing at 1500 degreesC for 15 minutes.

Intentional doping of aluminum in 4H and 6H SiC has been performed using a hot-wall CVD reactor. The dependence of aluminum incorporation on temperature, pressure, C/Si ratio, growth rate, and TMA flow has been investigated. The aluminum incorporation showed to be polarity dependent. The high aluminum incorporation on the Si-face is closely related to the carbon coverage on the SiC surface. Changes in process parameters changes the effective C/Si ratio close to the SiC surface. Increased growth rate and C/Si ratio increases the aluminum incorporation on the Si-face. Diffusion limited incorporation occurs at high growth rate. Reduced pressure increases the effective C/Si ratio, and at low growth rate, the aluminum incorporation increases initially, levels off at a critical pressure, and continues to decrease below the critical pressure. The aluminum incorporation showed to be constant in a temperature range of 50°C. The highest atomic concentration of aluminum observed in this study was 3·1017 and 8·1018 cm-3 in Si and C-face, respectively.

An unexpected presence of hydrogen in 4H-SiC was revealed by the observation of hydrogen related lines in the low-temperature photoluminescence (LTPL) spectrum after secondary ion mass spectrometry (SIMS) measurements. The lines were not observed before SIMS. The high-energy ions during SIMS are proposed to break the boron-hydrogen bonds. This phenomenon is observable only for a certain impurity concentration in the material due to the competition of various recombination channels during the LTPL experiment.

A brief survey is given of some recent results on doping of 4H- and 6H-SiC by ion implantation. The doses and energies used are between 10(9) and 10(15) cm(-2) and 100 keV and 5 MeV, respectively, and B and Al ions (p-type dopants) are predominantly studied. After low dose implantation (less than or equal to 10(10) cm(-2)) a strong compensation is observed in n-type samples and this holds irrespective of implantation temperature up to 600 degreesC. However, at higher doses (10(14)-10(15) Al/cm(2)) the rate of defect recombination (annihilation) increases substantially during hot implants (greater than or equal to 200 degreesC) and in these samples one type of structural defect dominates after past-implant annealing at 1700-2000 degreesC. The defect is identified as a dislocation loop composed of clustered interstitial atoms inserted on the basal plane in the hexagonal crystal structure. Finally, transient enhanced diffusion (TED) of ion-implanted boron in 4H-samples is discussed.

Epitaxially grown 4H-SiC structures with several heavily Al doped layers were used. The samples were annealed in Ar atmosphere in a RF-heated furnace between 1500 and 2900 degreesC for 0.5 to 3h. Secondary ion mass spectrometry (SIMS) was used to measure the aluminum concentration versus,depth as well as the lateral distribution (ion images). Transmission electron microscopy (TEM) was employed to study the crystallinity and determine phase composition after heat treatment. A solubility limit of 2x10(20) Al/cm(3) at 2000 degreesC is extracted. Ion images of the lateral Al distribution reveal a pronounced dependence on the Al content. Precipitate formation occurs after heat treatment at 1700 - 2000 degreesC when the Al concentration exceeds 2x10(20) cm(-3) and energy-filtered TEM (EFTEM) shows that the precipitates contain Al.

Deuterium was introduced in p-type SiC from a gas ambient. The samples were partially coated with 200 Angstrom thick metal layer of titanium, nickel, platinum or gold. Heat treatments were performed in the temperature range 500-800 degreesC during 4 h. Secondary ion mass spectrometry (SIMS) was used to measure the deuterium content after deuterium exposure. The catalytic metal coating is shown to play an important role for introducing deuterium into SiC. Nickel and platinum facilitate hydrogen incorporation in p-type SiC, which may be due to an increased hydrogen concentration at the metal/SiC interface and/or an increase the H+ ions to H ratio. No in-diffusion of deuterium is observed using titanium although large quantities of deuterium are stored in the titanium film. Furthermore, gold reveals an inert character and does not promote in-diffusion of deuterium.

From a systematic study of highly doped n-type 4H-SiC epilayers we observe a photoluminescence spectrum, which was previously associated with the recombination of a bound exciton at the neutral boron acceptor. Electrical measurements performed on these layers show clearly n-type conductivity. It was feasible to dope and measure reproducibly the layers from low 10(17) to mid 10(18) cm(-3). It was not possible to determine the doping from Capacitance Voltage measurements for the samples grown with the highest doping (>6.10(18) cm(-3)). However Secondary Ion Mass spectrometry did not reveal any boron impurities in the layers and shows good agreement with electrical measurements regarding the nitrogen concentration.

Sublimation epitaxy for fabrication of thick 4H-SiC layers has been studied with respect to surface morphology, structural quality, and purity. The surface morphology of thick (50-100 mum) epilayers is smooth, even though the growth rate was 100 mum/h. These surfaces are obtained within a parameter window for morphological stability. The structural perfection is confirmed by high-resolution X-Ray diffraction measurements and the epilayer quality is improved compared with the substrate. The limitation in purity is dependent mainly on the purity of the SiC source material. The growth system purity, mainly graphite and Ta parts of the growth crucible, is also of major importance. Results from intentional doping for high-resistive, semi-insulating and p-type material are presented.

This paper reviews recent secondary ion mass spectrometry (SIMS) work on (i) isotope shifts in ion implantation profiles, (ii) dopant profiles in silicon and beam-induced oxidation and (iii) surface roughness and profile broadening of Al(x)Ga1-(x)As/GaAs superlattice structures. Comparison is made with other techniques, and, in particular, the issues of depth resolution and conversion between sputtering time and sample depth are emphasized., 11th International Conference on Ion Beam Analysis (IBA-11), BALATONFURED, HUNGARY, JUL 05-09, 1993 NR 20140805

Zinc-diffusion doping of GaAs using metalorganic vapor-phase epitaxy and DEZn as a dopant source is evaluated. The dependence of the diffusion profile on DEZn flow and diffusion time is presented. Typical zinc concentrations and depths obtained are 10(19)-10(21) cm-3 and 40-200 nm, respectively. The largest concentration gradient obtained in this manner was four orders of magnitude in 500 angstrom, and the highest zinc concentration was measured as 2 x 10(21) cm-3 at a sample surface. A heterojunction bipolar transistor fabricated using zinc-diffusion doping of the base and a regrown emitter showed an f(max) of 50 GHz., NR 20140805