AIN thick films were grown on c-plane sapphire substrates by hydride vapor phase epitaxy at high temperature. The evolution of the strain state and crystal quality of AIN with increase of thickness were investigated b...AIN thick films were grown on c-plane sapphire substrates by hydride vapor phase epitaxy at high temperature. The evolution of the strain state and crystal quality of AIN with increase of thickness were investigated by transmission electron microscopy, field-emission scanning electron microscopy, Raman spectra and atomic force microscopy （AFM）. As the thickness increased, the stress in the epilayers decreased gradually, which was attributed to the reaction of dislocations at the first several microns in thickness. When the thickness was more than 20 μm, the stress was almost fully relaxed due to the formation of cracks. Wet etching experiments indicated that the dislocation density decreased with the increase of thickness. The AFM images showed that the density of dark spots on the surface obviously decreased and the atomic steps became straight as the thickness increased.展开更多
The Ti/Al/Ni/Au metals were deposited on undoped AlN films by electron beam evaporation. The influence of annealing temperature on the properties of contacts was investigated. When the annealing temperatures were betw...The Ti/Al/Ni/Au metals were deposited on undoped AlN films by electron beam evaporation. The influence of annealing temperature on the properties of contacts was investigated. When the annealing temperatures were between 800 and 950 ℃, the AlN-Ti/Al/Ni/Au contacts became ohmic contacts and the resistance decreased with the increase of annealing temperature. A lowest specific contacts resistance of 0.379 Ω·cm^2 was obtained for the sample annealed at 950 ℃. In this work, we confirmed that the formation mechanism of ohmic contacts on Al N was due to the formation of Al-Au, Au-Ti and Al-Ni alloys, and reduction of the specific contacts resistance could originate from the formation of Au2Ti and AlAu2 alloys. This result provided a possibility for the preparation of Al N-based high-frequency, high-power devices and deep ultraviolet devices.展开更多
基金Project supported by the National Basic Research Program of China(No.2012CB619305)the National Natural Science Foundation of China(Nos.61274127,61474133,61325022)the CAS Project of Introduction of Outstanding Technical Talent
文摘AIN thick films were grown on c-plane sapphire substrates by hydride vapor phase epitaxy at high temperature. The evolution of the strain state and crystal quality of AIN with increase of thickness were investigated by transmission electron microscopy, field-emission scanning electron microscopy, Raman spectra and atomic force microscopy （AFM）. As the thickness increased, the stress in the epilayers decreased gradually, which was attributed to the reaction of dislocations at the first several microns in thickness. When the thickness was more than 20 μm, the stress was almost fully relaxed due to the formation of cracks. Wet etching experiments indicated that the dislocation density decreased with the increase of thickness. The AFM images showed that the density of dark spots on the surface obviously decreased and the atomic steps became straight as the thickness increased.
文摘The Ti/Al/Ni/Au metals were deposited on undoped AlN films by electron beam evaporation. The influence of annealing temperature on the properties of contacts was investigated. When the annealing temperatures were between 800 and 950 ℃, the AlN-Ti/Al/Ni/Au contacts became ohmic contacts and the resistance decreased with the increase of annealing temperature. A lowest specific contacts resistance of 0.379 Ω·cm^2 was obtained for the sample annealed at 950 ℃. In this work, we confirmed that the formation mechanism of ohmic contacts on Al N was due to the formation of Al-Au, Au-Ti and Al-Ni alloys, and reduction of the specific contacts resistance could originate from the formation of Au2Ti and AlAu2 alloys. This result provided a possibility for the preparation of Al N-based high-frequency, high-power devices and deep ultraviolet devices.
