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An analysis is presented for obtaining spatial depth profiles of electronic defects in semiconductors from deep-level spectroscopic measurements performed in the constant-capacitance mode. Combined with the double-correlation technique proposed by Lefevre and Schulz, the new method offers significant advantages for measuring defect profiles. Deep-level transient spectroscopy (DLTS), performed in either the conventional capacitance-transient mode or the constant-capacitance mode, provides the energy levels of defect states in the semiconductor band gap. The double correlation DLTS technique (DDLTS) is used to define a narrow spatial observation window for defect profiling. However, in the DDLTS analysis of capacitance-transient data, specific approximations are required to deal with the change with time of the semiconductor depletion width during the transient response to a charging pulse. In the constant-capacitance mode, the depletion width is held constant by dynamically varying the applied voltage during the transient response, thus permitting more accurate measurements of defect profiles at high trap densities. Analytical expressions for computing the local trap density are derived, and experimental results are presented for damage profiles in self-implanted silicon.

The energy distribution of hot electrons in silicon has been investigated experimentally and theoretically by observation of the energy distribution of electrons emitted into vacuum from a reverse biased p-n junction 1000 A below the surface. This emission has been related by means of the Boltzmann transport equation to the mean free paths for optical phonon emission and impact ionization. Two experiments were performed. In the first, with the junction biased to avalanche breakdown, the product of the mean free paths effectively determines the attenuation length for electrons in the resulting nearly Maxwellian distribution. The dependence of the emitted current on the ^-layer thickness, which determines the attenuation length, and the field configuration within the junction were determined by removing thin calibrated layers (33 A) of silicon by boiling water oxidation. The second experiment, in which avalanche breakdown and its complications were avoided by optical generation of carriers, has been analyzed in terms of a plane source of electrons released a known distance below the surface at a given energy. The number of emitted electrons then has a maximum at an energy loss depending on the ratio of the mean free paths. The solution of the transport equation similar to that of Wolff, extended to include the initial transient in a field region, was fitted to the experimental data. A good fit was obtained using mean free paths for optical phonon emission of 60 A and for impact ionization of 190 A.

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We demonstrate the role and utility of lateral heat flow in the growth of single-crystal silicon islands on amorphous substrates. The thermal profile is varied on and around the islands by controlling the optical absorption using various thin-film structures. In this way, competitive nucleation from edges is suppressed and continued in-plane epitaxial zone growth is enhanced. We have succeeded in producing 20-μm-wide single-crystalline islands.