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Abstract: High-power P+P–N–N+ diodes (V RRM =2.5kV, I FAV =150A) with sputtered Mo layer at anode were annealed in the range 550–800°C with and without the presence of radiation defects from helium implantation (10MeV, 1×1012 cm−2). The devices were characterized using DLTS, spreading resistance, OCVD lifetime, leakage current, forward voltage drop and reverse recovery measurements. The diffusion of Mo from the 50nm thick surface layer was not registered even after 4h between 550 and 800°C in a rough vacuum. The DLTS confirms the existence of hole deep levels H1 and H2 in the He implanted devices with the Mo anode layer. Similar levels have been already found in the devices with Pt and Pd anode layers, but with different annealing behavior between 600 and 700°C. Contrary to that of the Pt and Pd, no radiation enhanced diffusion was found from the 50nm thick Mo surface layer in a rough vacuum. [Copyright &y& Elsevier]

Enhanced formation of shallow donors (SDs) in hydrogen or helium-irradiated and subsequently annealed float-zone n-type silicon is investigated. Ion energies, irradiation fluences and annealing temperatures were chosen in ranges typically used for local lifetime control in silicon power devices. Introduced radiation defects and SDs were investigated by deep-level transient spectroscopy and C–V profiling. Results show that radiation damage produced by helium ions remarkably enhances formation of thermal donors (TDs) when the annealing temperature exceeds 375°C, i.e. when the majority of vacancy-related recombination centres anneal out. Proton irradiation introduces hydrogen donors (HDs) which form a Gaussian peak at the proton end-of-range. Their concentration linearly increases with proton fluence and changes dramatically during post-irradiation annealing between 100 and 200°C since HD constituents are reacting with radiation damage. Their annealing in this temperature range is influenced by the electric field. If annealing temperature exceeds 400°C, HDs disappear and the excessive shallow doping is caused, as in the case of helium irradiation, by TDs enhanced by radiation damage. Shallow doping introduced by both hydrogen and helium can have a detrimental influence on blocking voltage of power diodes if high irradiation fluences or wrong annealing conditions are chosen. [ABSTRACT FROM AUTHOR]

Abstract: High-power diodes with the radiation enhanced diffusion (RED) of Pd are shown to have much higher ruggedness during the reverse recovery compared to that of the Pt. Anode doping profiles measured by spreading resistance technique after a 10MeV He implantation with subsequent annealing between 500 and 800°C reveal different compensation effects between the Pd and Pt. The in-diffusing Pd converts the n-type background doping concentration of N D =3×1013 cm−3 in the position of radiation defects to that of a p-type with about one order higher concentration. The created low-doped p-layer significantly increases ruggedness of diodes during reverse recovery. In the diodes with the Pt layer, only a modest compensation is observed, a conversion to a p-type layer is missing and robustness is much lower. The DLTS spectra for the Pt and Pd devices show a similar electronic structure and introduction rates of defects at 700°C, while they differ significantly at 600 and 650°C both for the majority and minority carriers. It is preliminary suggested that the strong compensation effect after the RED of Pd is caused by a high introduction rate of an acceptor deep level at the lower half of the silicon bandgap. [Copyright &y& Elsevier]