A new material structure with Al 0.22Ga 0.78As/In 0.15Ga 0.85As/GaAs emitter spacer layer and GaAs/In 0.15- Ga 0.85As/GaAs well for resonant tunneling diodes is designed and the corresponding device is fabricated.RTDs DC characteristics are measured at room temperature. Peak-to-valley current ratio and the available current density for RTDs at room temperature are computed.Analysis on these results suggests that adjusting material structure and optimizing fabrication processes will be an effective means to improve the quality of RTDs.
Optical filters capable of single control parameter based wide tuning are implemented and studied.A prototype surface micromachined 1 3μm Si based MOEMS (micro opto electro mechanical systems) tunable filter exhibits a continuous and large tuning range of 90nm at 50V tuning voltage.The filter can be integrated with Si based photodetector in a low cost component for coarse wavelength division multiplexing systems operating in the 1 3μm band.
A 1.55μm Fabry-Perot (F-P) thermo-optical t unable filter is fabricated.The cavity is made of amorphous silicon (a-Si) layer grown by electron-beam evaporation technique.Due to the excellent thermo-optical property of a-Si,the refractive index of the F-P cavity will be changed by heating;the transmittance resonant peak will therefore shift substantially.The measured tuning rang is 12nm, FWHM (full-width-at-half-maximum) of the transmissi on peak is 9nm,and heating efficiency is 0.1K/mW.The large FWHM is mainly due to th e non-ideal coating deposition and mirror undulation.Possible improvements to increase the efficiency of heating are suggested.
