Microstructures of GaN Buffer Layers Grown on Si(111) Using Rapic Thermal Process Low-Pressure Metalorganic Chemical Vapor Deposition

Microstructures of GaN buffer layers grown on Si(111)substrates using rapid thermal process low-pressure metalorganic chemical vapor deposition are investigated by an atomic force microscope(AFM)and a high-resolution transmission electron microscope(HBTEM).AFM images show that the islands appear in the GaN buffer layer after annealing at high temperature.Cross-sectional HBTEM micrographs of the buffer region of these samples indicate that there are bunched steps on the surface of the Si substrate and a lot of domains in GaN misorienting each other with small angles.The boundaries of those domains locate near the bunched steps,and the regions of the Him on a terrace between steps have the same crystal orientation.An amorphous-like layer,about 3nm thick,can also be observed between the GaN buffer layer and the Si substrate.

Study of Optical Nonlinearity in Hydrogenated Amorphous Silicon Carbide Film

Hydrogenated amorphous silicon carbide(a-Sic_(x):H)films were prepared by glow discharge technique with gas mixture of silane(SiH_(4))and methan(CH_(4)).The room-temperature optical bistability was demonstrated in uncoated a-SiC_(x):H films at the excitation wavelength about 532nm.The switch-on intensity of device is about 0.8 MW/cm^(2) and the switching time is in the nanosecond scale.The physical origin of the optical nonlin5arity in these materials is also discussed.

Subband Optical Transitions in a-Si:H Quantum Well Structures

The hydrogenated amorphous silicon(a-Si:H)/silicon carbide(a-SiCx:H)quantum well(QW)and superlattice structures were fabricated by glow discharge deposition.Wavelength differential absorption spectroscopy has been applied to study the subband transition in a-Si:H/a-SiC_(x):H Q W,and derivative spectra change clearly from a linear to a step-like form when a-Si:H well-layer thickness has decreased below 40Å.These results indicate that three-dimensional parabolic band transition is turned into subband transition in the a-Si:H QW.

Photoluminescence Excitation Spectroscopy and Light Emission Mechanism of Porous Silicon

Much information concerning the light emission mechanism can be extracted fromthe investigation of photoluminescence(PL)and photoluminescence excitation (PLE)spectroscopy. There were many reports on the relation between the spectroscopicproperties of porous silicon and the sample preparation and post processingconditions. Several kinds of light emission models have been proposed based onthese experiments. Some articles reported the results of spectroscopic properties ofporous silicon in relation with different excitation conditions and suggested that

Observations on temperature dependence of photoconductivity in hydrogenated amorphous silicon

It is well known that the photoconductive sensitivity is often used to roughly characterize the quality of amorphous semiconductors, because it involves not only the optical processes of carrier excitation, trapping and recombination but also the various transport mechanisms of excited carriers. The results published by many groups show that a wide range of properties can be observed in samples produced under a variety of deposition conditions.

Raman Scattering from Fine Zn Particles Coated with ZnO

Raman scattering from Zn fine spheric particles coated with ZnO of variable thickness is measured, and a broad line can be found. The Raman line shifts to lower frequency side with the increase of oxide thickness. A theoretical analysis based on the existence of surface phonon mode has been made. Agreement between experiment and theory is good.