We demonstrate noncontact measurements of the Hall mobility of doped semiconductor wafers with roughly 250 μm spatial resolution, using polarization rotation of focused beams of terahertz (THz) radiation in the presence of a static magnetic field. Quantitative and independent images of both carrier density and mobility of a doped semiconductor wafer have been obtained.

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Centrifugal separation of elements and isotopes in a rotating, magnetized column of highly ionized plasma is described. Such a centrifuge differs from prior plasma centrifuges in that the source of plasma is a laser-initiated vacuum arc, rather than a gas discharge. Detailed measurements are presented of the axial evolution of the radial plasma flux and separation profiles. Centrifugal separation increases rapidly with distance from the cathode plasma source, reaching an asymptotic value about 60 cm downstream. The separation is observed to increase exponentially with the square of the radius. The potential profile across the column was measured and found to be parabolic with radius. These observations are accounted for by a steady-state, multispecies, fluid model of the rotating plasma.

P-type, Be-doped GaInNAs layers (1100 Å thick) are grown on GaAs substrates by gas-source molecular beam epitaxy with a nitrogen radical beam source. High-resolution x-ray rocking curves show that the Ga0.892In0.108NxAs1−x peak shifts closer to the GaAs substrate peak with increasing N concentration, indicating reduced strain. After rapid thermal annealing (RTA) at 700 °C for 10 s, the Ga0.892In0.108As sample suffers strain relaxation, but the N-containing samples remain pseudomorphically strained, suggesting better thermal stability of GaInNAs. The wavelength of room-temperature photoluminescence redshifts from 0.988 to 1.276 μm, due to large band gap bowing, with N concentration increased from 0 to 0.024. Secondary ion mass spectrometry results show no Be diffusion, but hydrogen incorporation alongside N. The free carrier concentration is decreased by one order of magnitude mainly due to H passivation, but after RTA at 700 °C, it is increased to half that of GaInAs due to the reduced H concentration. The product of carrier concentration and Hall mobility is increased from one-tenth to about half that of the GaInAs sample.

Scanning spreading resistance microscopy (SSRM) is an analytical technique originally developed for measuring two-dimensional carrier distribution in Si device structures with high spatial resolution. It is in essence an atomic force microscope equipped with a conducting tip that is biased relative to the sample. The spreading resistance value derived from the measured electrical current is a function of the local carrier concentration at the surface region surrounding the probe’s tip. In this letter, we report the successful application of SSRM to the analysis of InP semiconductor device structures. We imaged a multilayer epitest structure, and a cross section of a three-dimensional structure in which we observed lateral Zn-dopant diffusion. Comparison of the SSRM profiles with one-dimensional secondary ion mass spectrometry depth profiles shows good qualitative agreement. SSRM analysis of InP-based device structures was found to be much simpler than that of Si structures: there is no need for surface preparation of the cleaved surface, a lower tip force is required, and metal tips, rather than doped diamond can be used.