DC Characteristics of Lattice-Matched InAlN/AlN/GaN High Electron Mobility Transistors

Lattice-matched InAlN/AlN/GaN high electron mobility transistors (HEMTs) grown on sapphire substrate by using low-pressure metallorganic chemical vapor deposition were prepared, and the comprehensive DC characteristics were implemented by Keithley 4200 Semiconductor Characterization System. The experimental results indicated that a maximum drain current over 400 mA/mm and a peak external transconductance of 215 mS/mm can be achieved in the initial HEMTs. However, after the devices endured a 10-h thermal aging in furnace under nitrogen condition at 300 ℃, the maximum reduction of saturation drain current and external transconductance at high gate-source voltage and drain-source voltage were 30% and 35%, respectively. Additionally, an increased drain-source leakage current was observed at three-terminal off-state. It was inferred that the degradation was mainly related to electron-trapping defects in the InAlN barrier layer.

n-type Polycrystalhne Si Thick Films Deposited on SiN_x-coated Metallurgical Grade Si Substrates

For photovoltaic applications,low-cost SiNx-coated metallurgical grade silicon（MG-Si） wafers were used as substrates for polycrystalline silicon（poly-Si） thick films deposition at temperatures ranging from 640 to880 ℃ by thermal chemical vapor deposition.X-ray diffraction and Raman results indicated that high-quality poly-Si thick films were deposited at 880 ℃.To obtain n-type poly-Si,the as-deposited poly-Si films were annealed at 880 ℃ capped with a phosphosilicate glass.Electrical properties of the n-type poly-Si thick films were investigated by four-probe and Hall measurements.The carrier concentration and electron mobility of the n-type poly-Si film was estimated to be 1.7 x 1019cm-3and 68.1 cm2V-1s-1,respectively.Highquality poly-Si thick films deposited on MG-Si wafers are very promising for photovoltaic applications.