Margareta K. Linnarsson

Electrical activation of high concentrations of N+ and P+ ions implanted into 4H–SiC

Comparative Hall effect investigations are conducted on N- and P-implanted as well as on (N+P)-coimplanted 4H–SiC epilayers. Box profiles with three different mean concentrations ranging from 2.5×1018 to 3×1020 cm−3 to a depth of 0.8 μm are implanted at 500 °C into the (0001)-face of the initially p-type (Al-doped) epilayers. Postimplantation anneals at 1700 °C for 30 min are conducted to electrically activate the implanted N+ and P+ ions. Our systematic Hall effect investigations demonstrate that there is a critical donor concentration of (2–5)×1019 cm−3. Below this value, N- and P-donors result in comparable sheet resistances. The critical concentration represents an upper limit for electrically active N donors, while P donors can be activated at concentrations above 1020 cm−3. This high concentration of electrically active P donors is responsible for the observed low sheet resistance of 35 Ω/□, which is about one order of magnitude lower than the minimum sheet resistance achieved by N implantation.

Annealing behavior between room temperature and 2000 °C of deep level defects in electron-irradiated n-type 4H silicon carbide

The annealing behavior of irradiation-induced defects in 4H-SiC epitaxial layers grown by chemical-vapor deposition has been systematically studied by means of deep level transient spectroscopy (DL ...

Nitrogen doping of epitaxial silicon carbide

Abstract Intentional doping with nitrogen of 4H- and 6H-SiC has been performed using a hot-wall CVD reactor. The nitrogen doping dependence on the temperature, pressure, C/Si ratio, growth rate and nitrogen flow has been investigated. The nitrogen incorporation for C-face material showed to be C/Si ratio independent, whereas the doping decreased with increasing C/Si ratio for the Si-face material in accordance with the “site-competition” model. The nitrogen incorporation was constant in a temperature “window” of 75°C on Si-face material indicating a mass transport limited incorporation. Increasing the growth rate resulted in a decrease of nitrogen incorporation on Si-face but an increase on C-face material. Finally, a comparison between previously published results on cold-wall CVD-grown material and the present hot-wall-grown material is presented.

ELECTRICALLY ACTIVE POINT DEFECTS IN N-TYPE 4H-SIC

An electrically active defect has been observed at a level position of ∼ 0.70 eV below the conduction band edge (Ec) with an extrapolated capture cross section of ∼ 5×10−14 cm2 in epitaxial layers ...

Aluminum doping of epitaxial silicon carbide

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 ...

Transient enhanced diffusion of implanted boron in 4H-silicon carbide

Experimental evidence is given for transient enhanced diffusion of boron (B) in ion-implanted silicon carbide (SiC). The implanted B is diffusing several mu m into the samples when annealed at 1600 ...

Hydrogen passivation of silicon carbide by low-energy ion implantation

Ion implantation of deuterium is performed to investigate the mobility and passivating effect of hydrogen in epitaxial α-SiC (polytypes 4H and 6H). To avoid excessive damage and the resulting trapping of hydrogen, the implantation is performed with low energy (600 eV 2H2+). The 2H depth profile is analyzed by secondary ion mass spectrometry. Electrical properties are measured by capacitance–voltage profiling and admittance spectroscopy. In p-type SiC, hydrogen diffuses on a μm scale even at room temperature and effectively passivates acceptors. In n-type SiC, the incorporation of H is suppressed and no passivation is detected.

Solubility limit and precipitate formation in Al-doped 4H-SiC epitaxial material

Heavily Al-doped 4H-SiC structures have been prepared by vapor phase epitaxy. Subsequent anneals have been carried out in an Ar atmosphere in a rf-heated furnace between 1500 degreesC and 2000 degr ...

Ion implantation of silicon carbide

Ion implantation is an important technique for a successful implementation of commercial SiC devices. Much effort has also been devoted to optimising implantation and annealing parameters to improve the electrical device characteristics. However, there is a severe lack of understanding of the fundamental implantation process and the generation and annealing kinetics of point defects and defect complexes. Only very few of the most elementary intrinsic point defects have been unambiguously identified so far. To reach a deeper understanding of the basic mechanisms SiC samples have been implanted with a broad range of ions, energies, doses, etc., and the resulting defects and damage produced in the lattice have been studied with a multitude of characterisation techniques. In this contribution we will review some of the results generated recently and also try to indicate where more research is needed. In particular, deep level transient spectroscopy (DLTS) has been used to investigate point defects at very low doses and transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) are used for studying the damage build-up at high doses.

Diffusion of Zn and Mg in AlGaAs/GaAs structures grown by metalorganic vapor-phase epitaxy

The diffusion of thin, highly p‐doped layers in AlGaAs/GaAs single‐ and double‐heterostructures, grown by metalorganic vapor‐phase epitaxy, was studied with C‐V etch profiling and secondary ion mass spectroscopy. The effect of different post‐growth heat treatments was investigated and diffusion coefficients for both magnesium and zinc were measured. It was found that Mg diffuses about twice as fast Zn and that the order of magnitude of the diffusion coefficient is 10−14 cm2 s−1 at 900 °C, the exact value being process and concentration dependent. A model based on the interstitial–substitutional diffusion mechanism with suitable kinetic limitations was successfully used to simulate the observed dopant concentration profiles.We also found an anomalous strong diffusion of zinc from GaAs into highly n‐doped AlGaAs. Detailed results on this and other structures are presented and implications for optimal design of heterostructure devices such as bipolar transistors are discussed.