Influences of high-temperature annealing on atomic layer deposited Al2 O3/4H-SiC

High-temperature annealing of the atomic layer deposition (ALD) of Al2O3 films on 4H-SiC in O 2 atmosphere is studied with temperature ranging from 800℃ to 1000℃. It is observed that the surface morphology of Al2O3 films annealed at 800℃ and 900℃ is pretty good, while the surface of the sample annealed at 1000℃ becomes bumpy. Grazing incidence X-ray diffraction (GIXRD) measurements demonstrate that the as-grown films are amorphous and begin to crystallize at 900℃. Furthermore, C-V measurements exhibit improved interface characterization after annealing, especially for samples annealed at 900℃ and 1000℃. It is indicated that high-temperature annealing in O2 atmosphere can improve the interface of Al2O3 /SiC and annealing at 900℃ would be an optimum condition for surface morphology, dielectric quality, and interface states.     

Photon higher-order squeezing effects of the q analogue of a single-mode field interacting with a Ξ-type three-level atom

The nonlinear theory of interaction between the q analogue of a single-mode field and a Ξ-type threelevel atom has been established. And the formal solution of the Schrodinger equation in the representation and its average number are obtained. Then, the photon squeezing effects are studied through numerical calculation. The results show that the q deformation nonlinear action has a lot of influence on the quantum coherence and quantum properties. When q approaches 1, the theory reduces to the common linear theory.     

Design and fabrication of a compact multimode interference splitter with silicon photonic nanowires

A compact multimode interference （MMI） splitter with silicon photonic nanowires on silicon-on-insulator （SOI） substrate is designed and fabricated. The footprint of the MMI section is only approximately 3×10 （μm）. The simulation results show that the device may have a low excess loss of 0.04 dB. The transmission loss of the silicon photonics wire is measured to be 0.73±0.3 dB/mm. The compact size and low transmission loss allow the device to be used in ultra-compact photonic integrated circuits. The device exhibits a good light splitting function. In a spectral range of 1549-1560 nm, the excess loss is 1.5 dB and the average imbalance between the two channels is 0.51 dB.     

Numerical and experimental study of the mesa configuration in high-voltage 4H–SiC PiN rectifiers

The effect of the mesa configuration on the reverse breakdown characteristic of a SiC PiN rectifier for high-voltage applications is analyzed in this study.Three geometrical parameters,i.e.,mesa height,mesa angle and mesa bottom corner,are investigated by numerical simulation.The simulation results show that a deep mesa height,a small mesa angle and a smooth mesa bottom(without sub-trench) could contribute to a high breakdown voltage due to a smooth and uniform surface electric field distribution.Moreover,an optimized mesa structure without sub-trench(mesa height of 2.2 μm and mesa angle of 20°) is experimentally demonstrated.A maximum reverse blocking voltage of 4 kV and a forward voltage drop of 3.7 V at 100 A/cm~2 are obtained from the fabricated diode with a 30-μm thick N~- epi-layer,corresponding to 85% of the ideal parallel-plane value.The blocking characteristic as a function of the JTE dose is also discussed for the PiN rectifiers with and without interface charge.     

Uneven splitting-ratio 1×2 multimode interference splitters based on silicon wire waveguides

Two types of 1×2 multi-mode interference(MMI) splitters with splitting ratios of 85:15 and 72:28 are designed.On the basis of a numerical simulation,an optimal length of the MMI section is obtained.Subsequently,the devices are fabricated and tested.The footprints of the rectangular MMI regions are only 3×18.2 and 3×14.3(μm).The minimum excess losses are 1.4 and 1.1 dB.The results of the test on the splitting ratios are consistent with designed values.The devices can be applied in ultra-compact photonic integrated circuits to realize the "tap" function.