Resonant tunneling in multiple-barrier structures with arbitrary potential profile is studied theoretically. Analytical expressions of the transmission coefficient and the resonance condition are derived by taking into account the mass difference between well and barrier layers. The basic barrier unit in the periodic multiple-barrier structure may be a compound-barrier structure, and the simplest compound-barrier unit is the double-barrier unit. Two independent resonance conditions exist in the multiple-barrier structures with compound-barrier unit and both the subband gap energy and the energy value at the center of the subband gap may be determined analytically and independently for the multiple-barrier structure with doublebarrier unit.

A theoretical analysis has been carried out to compare the resonance condition in the asymmetric double-barrier structure with that in the symmetric triple-barrier one. It is. found that. the triple-barrier structure may be considered as two quasidouble-barrier structures whose resonance condition may decide the resonance levels in the triple-barrier structure. It is confirmed that two modes exist in the triple-barrier structure: one is "normal mode consisting of doublet and the other is degenerated mode of singlet. The critical condition between the two modes is given and its physical meaning is examined. Moreover, it is confirmed that both the normal mode and the degenerated mode exist also in symmetric n-fold barrier structures (n≥3).

A new design of power supply based on the idea of switched capacitors, as applied to pocket computer systems, is presented. This new type of power supply is inductorless and, consequently, suitable for hybridization and even monolithic integration. The new design is also based on distinguishing characteristics of pocket digital computer systems, in which a switched-capacitor converter can work well, since minimal regulation is required. The new device may enable the pocket computer system to be powered by only one battery, resulting in a simple topology. Two switched-capacitor converters, +12 V/-12 V, +5 V and +5 V/+12 V, -12 V, are shown, respectively, as an example for demonstrating the basic principle and its performance. PSPICE simulation and laboratory models show good results for this new type of power supply.

Intense wide-band photoluminescence (PL) was observed at room temperature from both SiC thin films grown on silicon substrates by hot-filament chemical vapor deposition and anodized SiC thin films formed by electrochemical anodization in HF-ethanol solution. It was found that prolonged irradiation with ultraviolet light from a He-Cd laser (325nm, 10mW) generally enhanced the PL intensity of as-grown SiC but induced a new PL band in anodized SiC at room temperature. The light-induced PL emission in anodized SiC was centered at the energy between 2.1 and 2.2eV in comparison with the initial peak position of about 1.9eV. These effects were also temperature dependent.

Intense photoluminescence (PL) from porous-like SiC has been observed at room temperature. The samples were prepared by electrochemical anodization from nanocrystalline SiC thin films grown on Si (100) substrates in hot filament chemical vapor deposition. It has been found that a light-induced enhancement of the PL intensity will take place if the incident light beam from an He-Cd laser (325nm, 10mW) is employed for the excitation. Blue-shift of the PL peak energy from about 1.9 eV of as-anodized samples to about 2.1 eV and an accompanied spectral widening have also been observed for a long enough irradiation time. However, the novel effects have not been observed at low temperature. Origin of the light-induced change is suggested to be related to some light-induced metastable defects.