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 novel technique has been developed to lithographically make fine patterns on PZT films. Employing chemical modification in acetylacetone (AcAc), we have obtained an UV photosensitive PZT sol from which the PZT films to be patterned can be prepared. With methanol as solvent and AcAc as chemical modifier, three sols used to compose the PZT coating sol are obtained from Zirconium oxynitrate (ZrO(NO3)2), lead acetate (Pb (CH3COO)2), and tetrabutyl titanate ((C4H9O)4Ti), respectively. By means of UV-vis and FT-IR spectrophotometers we have found that AcAc can associate with Zr, Pb, and Ti ions to form three chelate complexes, the UV absorption peaks of which are located at wavelength 304, 315 and 329 nm, respectively. However, the photosensitive PZT coating sol has UV absorption peak at around 312 nm. Both the chelate complexes in sol and the UV absorption peak can be remained in the gel films. When the photosensitive PZT gel film is irradiated by UV light containing 312 nm wavelength, its solubility in solvents such as alcohol, acetone and so on is reduced remarkably, while the UV absorption peak disappears with the dissociation of the chelate complexes correspondingly. Utilizing the characteristics, a fine pattern can be obtained by irradiation of UV light on the PZT gel film through a pattern mask and dissolving the non-irradiated area in suitable solvent. After annealing at 680

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 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.

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).

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.

A SiC light-activated Darlington heterojunction transistor is proposed for anti-EMI (electromagnetic interference) applications, in which a monolithically integrated SiCGe/SiC pn heterojunction photodiode is employed to produce a light-induced base current for triggering the transistor. Performance of the proposed light-activated power switch was simulated using MEDICI tools. Feasibility of the proposal is confirmed by its good light-activation characteristics obtained from the simulation. The simulation also demonstrates that good I-V characteristics with a light-independent turn-on voltage knee of about 5 V may be achievable to the light-activated power switch has.

SiCGe/SiC heterojunction structure is required in development of SiC optoelectronic devices and light-activated switching devices. We present in this paper a primary attempt to grow the ternary alloy SiCGe on SiC substrates under varied growth conditions in a conventional hot-wall CVD system. SiH4, GeH4 and C3H8 were employed as silicon, germanium and carbon sources, respectively. The samples were measured by means of SEM, XPS, XRD, optical absorption, etc. Two different growth modes i.e., island growth and porous growth were observed. It has been shown that germanium atoms can be effectively incorporated into the ternary alloys, which makes their optical gaps to be narrowed with increasing Ge content. However, incorporation of Ge induces a heavy lattice mismatch, which limits the film thickness by the formation of mismatch defects. It has been shown that use of a buffer layer can effectively improve the growth quality of the ternary alloy.

Optoelectronic characteristies of the SiCl-ZGeZ/SiC heterojunction photodiode are simulated using MEDICI after the theoretical investigation of key properties for SiCl-xGex. The calculations show that SiCl-xGex/SiC with x=0.3 may have a small lattice mismatch with 3C-SiC and a good response to the visible light and the near infrared light. The response spectrum of the SiCl-xGex/SiC heterojunction photodiode, which consists of a p-type SiCl-xGex absorption layer with a doping concentration of 1×1015cm-3 ,a thickness of 1.6μm and x=0.3, has a peak of 250mA/W at 0.52μm and the peak can even reach 102mA/W at 0.7μm.

In this paper, we present a novel method to grow 3C-SiC crystal in a liquid-phase epitaxy-like manner, but without any substantial substrate. The starting material to be used in this method is the 3C-SiC-thin film deposited on Si substrate in a gas-phase heteroepitaxial technology. The free 3C-SiC film which remained of the molten Si substrate epitaxially grows up from the Si solution saturated by SiC in a highly purified graphite crucible heated by an inductive heater. XRD, XPS and Raman spectroscopy were used to characterize the samples. The only one peak with full width at half maximum (FWHM) of 0.2 at 20 = 35.65