Chengyue Yang

Uneven splitting-ratio 1 \times 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.

Analysis of the inhomogeneous barrier and phase composition of W/4H-SiC Schottky contacts formed at different annealing temperatures

The electrical characteristics of W/4H-SiC Schottky contacts formed at different annealing temperatures have been measured by using current–voltage–temperatures (I–V–T) and capacitance–voltage–temperatures (C–V–T) techniques in the temperature range of 25 °C–175 °C. The testing temperature dependence of the barrier height (BH) and ideality factor (n) indicates the presence of inhomogeneous barrier. Tungs model has been applied to evaluate the degree of inhomogeneity, and it is found that the 400 °C annealed sample has the lowest T 0 of 44.6 K among all the Schottky contacts. The barrier height obtained from C–V–T measurement is independent of the testing temperature, which suggests a uniform BH. The x-ray diffraction (XRD) analysis shows that there are two kinds of space groups of W when it is deposited or annealed at lower temperature (≤ 500 °C). The phase of W2C appears in the sample annealed at 600 °C, which results in the low BH and the high T 0. The 500 °C annealed sample has the highest BH at all testing temperatures, indicating an optimal annealing temperature for the W/4H-SiC Schottky rectifier for high-temperature application.