Zhiming Chen

Ultraviolet-light-enhanced luminescence in SiC thin films grown on Si by hot filament chemical vapor deposition and ultraviolet-light-induced luminescence in anodized SiC

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 (325 nm, 10 mW) 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 2.2 eV in comparison with the initial peak position of about 1.9 eV. These effects were also temperature dependent.

Light induced luminescence centers in porous SiC prepared from nano-crystalline SiC grown on Si by hot filament chemical vapor deposition

Abstract Intense photoluminescence (PL) was observed at room temperature from porous SiC samples prepared in electrochemical anodization from nano-crystalline SiC thin films grown on Si (100) substrates by hot filament chemical vapor deposition. Raman scattering spectroscopy and high-resolution transmission electron microscopy confirmed the nano-crystalline structure of the host films. For the porous samples formed under weaker anodization conditions, it was found that prolonged irradiation with ultraviolet (UV) light from a He–Cd laser (325 nm, 10 mW) can induce an enhanced new PL band and change the peak energy from 1.9 eV to 2.1 eV at room temperature. A defect model is suggested to explain the UV light induced PL change in porous SiC.

Epitaxial growth of cubic silicon carbide on silicon by sublimation method

Cubic silicon carbide (3C-SiC) is the most promising material for active devices. Most researches of 3C-SiC epitaxial technology have been focused on chemical vapor deposition (CVD) in the past, but the growth rate of CVD is low. We attempt to grow epitaxial 3C-SiC on Si by sublimation method according to bulk sublimation growth technology. The typical sample is characterized by X-ray diffraction and Raman scattering spectroscopy. The results reveal that the sample is well crystalline.

Liquid phase epitaxial growth of 3C-SiC films deposited on Si

Abstract 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 2θ=35.65° in XRD is attributed to the diffraction of (111) planes in 3C-SiC. The energy difference between C1s and Si2p binding energy in XPS data is 183.2 eV, which is well consistent with the result published before for single crystal 3C-SiC. Although the only sharp and strongest peak at 796.6 cm−1 in the Raman spectrum also confirms the crystal structure, the additional broadened weak peak at 523.6 cm−1 may imply the existence of some lattice defects related to nitrogen unintentionally introduced in the growth process.

Photoluminescence from Porous-Like SiC and Its Light-Induced Enhancement

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 (325 nm, 10 mW) 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.

Simulation of a near infrared light-activated 4H-SiC Darlington transistor switches

The novel near infrared light-activated Darlington heterojunction transistor power switch made of SiC has been proposed, in which SiCGe/SiC pn is employed to produce a base current by means of optical illumination. By using two-dimensional numerical simulation MEDICI, the SiCGe/SiC photodetector can be triggered by a near infer-red laser beam if the composition parameters of the Sil-x-yCxGey have been chosen properly. Performance of the near Infrared light-activated power switch was simulated, which has shown that the light-activated device has very good switching characteristics at 0.85/spl mu/m for optical intensity of 1.0 Watt/cm2. Based on our simulation results, the distribution of current density predicts that the auxiliary transistor is turned on at first by a low density of photocurrent and then the main transistor is turned on. The collector current of the device in the on-state is concentrated in a region underneath the main emitter.

ROOM TEMPERATURE PHOTOLUMINESCENCE OF POLYCRYSTALLINE SIC PREPARED FROM CARBON-SATURATED SI MELT

Intense photoluminescence (PL) has been observed at room temperature from the polycrystalline SiC samples prepared from carbon-saturated Si melt at a temperature ranging from 1500 to 1650°C. Composition and structure of the samples have been confirmed by means of X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. PL measurements with 325 nm UV light excitation revealed that the room temperature PL spectrum of the samples consists of 3 luminescent bands, the peak energies of which are 2.38 eV, 2.77 eV and 3.06 eV, respectively. The 2.38 eV band is much stronger than the others. It is suggested that some extrinsic PL mechanisms associated with defect or interface states would be responsible to the intensive PL observed at room temperature.

Fabrication and characteristics of a Si multiple-quantum dots single electron transistor on SIMOX substrate

We report Si-based multiple-quantum dots single electron transistors (SETs) on p-type SIMOX substrates, based on electron beam (EB) lithography and reactive ion etching (RIE) processes. These processes offer controlled fabrication of the quantum wires (QWs) and quantum dots (QDs). Coulomb blockade and single electron tunneling are observed in the SETs.