The effect of surface morphology of 6H-SiC substrate on the ohmic contact properties of Ti/6H-SiC structure is studied. The H-terminated surface on Si-face 6H-SiC is obtained by both dipping SiC into HF acid solution for 15 s and thermal heating SiC in hydrogen atmosphere at 1100 ℃ for 10 min, while the H-terminated surface on C-face 6H-SiC could be obtained only by the latter method. Ti is deposited on Si-face and C-face SiC substrates with H-terminated surfaces and ohmic contact is obtained without high-temperature annealing.
The 3C-SiC thin films used herein are grown on Si substrates by chemical vapor deposition. A1 contacts with differ- ent thickness values are deposited on the 3C-SiC/Si （100） structure by the magnetron sputtering method and are annealed at different temperatures. We focus on the effects of the annealing temperature on the ohmic contact properties and mi- crostructure of A1/3C-SiC structure. The electrical properties of A1 contacts to n-type 3C-SiC are characterized by the transmission line method. The crystal structures and chemical phases of A1 contacts are examined by X-ray diffraction, Raman spectra, and transmission electron microscopy, respectively. It is found that the A1 contacts exhibit ohmic contact behaviors when the annealing temperature is below 550 ℃, and they become Schottky contacts when the annealing tem- perature is above 650 ℃. A minimum specific contact resistance of 1.8 × 10-4 Ω cm2 is obtained when the A1 contact is annealed at 250 ℃.
A high-quality Ga2O3 thin film is deposited on an SiC substrate to form a heterojunction structure. The band alignment of the Ga2O3/6H-SiC heterojunction is studied by using synchrotron radiation photoelectron spectroscopy, The energy band diagram of the Ga2O3/6H-SiC heterojunction is obtained by analysing the binding energies of Ga 3d and Si 2p at the surface and the interface of the heterojunction. The valence band offset is experimentally determined to be 2.8 eV and the conduction band offset is calculated to be 0.89 eV, which indicate a type-II band alignment. This provides useful guidance for the application of Ga2O3/6H-SiC electronic devices.
This paper reports that the （Ga, Co）-codoped ZnO thin films have been grown by inductively coupled plasma enhanced physical vapour deposition. Room-temperature ferromagnetism is observed for the as-grown thin films. The x-ray absorption fine structure characterization reveals that Co2＋ and Ga3＋ ions substitute for Zn2＋ ions in the ZnO lattice and exclude the possibility of extrinsic ferromagnetism origin. The ferromagnetic （Ga, Co）-codoped ZnO thin films exhibit carrier concentration dependent anomalous Hall effect and positive magnetoresistance at room tempera- ture. The mechanism of anomalous Hall effect and magneto-transport in ferromagnetic ZnO-based diluted magnetic semiconductors is discussed.
Undoped and V-doped 6H-SiC single crystals have been grown by the physical vapor transport method.The V concentration is determined to be 3.76×10^17 at/cm^3 and 6.14×10^17 at/cm^3 by secondary ion mass spectrometry for low V-doped and high V-doped SiC samples,respectively.The undoped 6H-SiC shows diamagnetism,while the V-doped 6H-SiC exhibits weak ferromagnetism.The lower V-doped sample shows stronger ferromagnetism compared to that of the higher V-doped sample.However,the structural characterization indicates that the lower V-doped SiC has a relative poor crystalline quality.It is found that both V dopants and defects are essential for introducing ferromagnetic exchange in V-doped SiC single crystals.
