Showing papers by "Youdou Zheng published in 2001"

Crystal tilting in the epitaxial laterally overgrown GaN films on sapphire substrate by hydride vapor phase epitaxy

Abstract: Crystal tilts in the lateral overgrowth of GaN over SiO/sub 2/ mask on Sapphire Substrate by HVPE away from the opening region are demonstrated and characterized by scanning electron (SEM) and high resolve x-ray diffraction (HRXRD). The tilts and stripe morphologies are directly related to the mask width and "fill factors" (ratio of stripe opening width to stripe period). It is found that the growth condition, such as the introduction HCl, C/sub 3/H/sub 8//H/sub 2/ and the growth rate also have a significant effect on the wing tilt. The mechanisms of these factors affecting the wing tilts and stripe morphologies are discussed respectively.

Epitaxial lateral overgrowth of GaN on molecular beam epitaxy GaN buffer layers on Si substrates by hydride vapour phase epitaxy

Abstract: Hydride vapour phase epitaxy GaN epitaxial lateral overgrowth (ELO) materials were grown on patterned molecular beam epitaxy GaN buffer layers on Si (111) substrates. The ELO process leads to an improvement in the structural properties of the GaN on Si. The impact of the growth conditions such as substrate temperature and NH3 partial pressure (or flow rate) are reported for growth on these substrates. Continuous ELO materials have been obtained on a small period of ELO substrate with a high density of pits on the sample surface. The role of Si gas phase transport on the ELO materials is discussed.

Switching kinetics of interface states in deep submicrometre SOI n-MOSFETs

Abstract: Switching kinetics characteristics of interface traps in deep-submicrometre SOI n-MOSFETs have been investigated by random telegraph signals (RTSs). Two different types of behaviour of noising centres, Coulomb-attractive and Coulomb-repulsive centres, have been observed. By studying the gate bias and temperature dependence of the transition time and amplitude of the RTSs caused by the noising centres, it has been demonstrated experimentally that a thermally activated process may dominate for Coulomb-repulsive centres, while quantum mechanical tunnelling is a favoured process for Coulomb-attractive centres. In particular, RTSs with very large amplitude (>60%), which are almost independent of measurement temperature and gate bias, are observed in an ultra-narrow channel, which is well described by the quantum tunnelling model.

Epitaxial lateral overgrowth of GaN by HVPE and MOVPE

Abstract: Epitaxial lateral overgrowth (ELO) of GaN on SiO2 masked (0001) GaN substrate has been investigated by using chloride-based growth chemistries via hydride vapor phase epitaxy and metalorganic vapor phase epitaxy with diethylgallium chloride as the Ga source. It has been found that both the lateral and vertical growth rate, and geometric morphology of lateral overgrown GaN prisms are dependent on growth conditions (growth temperature and V/III ratio) and orientations. A high growth temperature and low V/III ratio is helpful to increase the lateral growth rate and flatten the top c-plane of GaN prisms. High quality coalesced flat-top ELO GaN has been fabricated by HVPE and no void is observable at the coalescence interface.

Structural study of chemical vapor deposition of Si on GaN

Abstract: We have grown high quality Si epilayers on wurtzite gallium nitride substrate by low-pressure chemical vapor deposition. X-ray photoelectron spectra and Auger electron spectra were employed to analyze the components and chemical structures of Si/GaN. The results indicated that there was nitrogen diffusion from the GaN layer to the Si layer and substitutional N accumulation near the interface, which agreed with carrier concentration obtained from electrical conductivity measurements.