• Journal of the Korean Ceramic Society
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• v.35 no.5
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• pp.486-492
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• 1998

Silicon carbide (SiC) thin films were deposited on the porous silicon substrates by chemical vapour de-position(CVD) using MTS as a source material. The deposited films were ${\beta}$-SiC with poor crystallity con-firmed by XRD measurement. It was considered that the films showed the mixed characteistics of cry-stalline and amorphous SiC where amorphous SiC where amorphous SiC played a role of buffer layer in interface between as-dep films and Si substrate. The buffer layer reduced lattice mismatch to some extent the generally occurs when SiC films are deposited on Si. The low temperature (10K) PL (phtoluminescence) studies showed two broad bands with peaks at 600 and 720 for the films deposited at 1100$^{\circ}C$ The maximum PL peak of the crystalline SiC was observed at 600 nm and the amrophous SiC of 720 nm was also confirmed. PL peak due the amorphous SiC was smaller than that of the crystalline SiC, PL of porous Si might be disapperared due to densification during heat treatment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.7
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• pp.564-569
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• 2002

Heteroepitaxial GaN films were grown on sapphire substrates in order to study the effects of the buffer layer's surface roughness and thermal treatment on the epitaxial layer's quality. For this, GaN buffer layers were grown at $550^{\circ}C$ with various TMGa flow rates and durations of growth, and annealed at $1010^{\circ}C$ for 3 min after the temperature was raised by 23 ~ $92^{\circ}C/min$, and then GaN epitaxial layers were grown at $1000^{\circ}C$. It has been found that the buffer layer's surface roughness and the thermal treatment condition are critical factors on the quality of the epitaxial layer. When a buffer layer was frown with a TMGa flow rate of $24\mu mole/min$ for 30 sec, the surface roughness of the buffer lather was minimum and when the thermal ramping rate was $30.6^{\circ}C/min$ on this layer, the successively grown epitaxial layer's crystalline and optical qualities were optimized with a specular morphology. The minimum full width at half maximum(FWHM) of GaN(0002) x-ray diffraction peak and that of near-band-edge(NBE) peak from a room temperature photoluminescence (PL) were 5 arcmin and 9 nm, respectively.

• Korean Journal of Optics and Photonics
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• v.3 no.3
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• pp.183-190
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• 1992

Luminescence properties of asymmetric double quantum well structure composed of $Al_x/Ga_{1-x}$ /As AIAs/GaAs have been studied by steady state and time-resolved photoluminescence and phtoluminescence excitation spectroscopy at low temperature. Two quantum well samples with different barrier thickness (15$\AA$ and 150$\AA$) were prepared to investigate the dependence of tunneling characteristics on barrier thickness. The abscence of excitonic recombination peak from $Al_x/Ga_{1-x}$As well for the 15$\AA$ barrier sample indicates a very fast electron tunneling to GaAs well. Meanwhile, T-X transition between well and barrier is supposed to be a major route for the fast decay of luminescence from $Al_x/Ga_{1-x}$As well in the 150$\AA$ barrier sample. Time-resolved photduminescence from GaAs well of 15$\AA$ sample shows the exsitence of the rise with 100 ps which is attributed to the hole tunneling.