Study On Transparent And Conductive Cdln₂O₄ Thin Films And Measurement Of High-Speed Photodetector Frequency Response

(1) Study on transparent and conductive CdIn₂O₄ thin filmsTransparent and conductive oxides CdIn₂O₄ thin films were prepared by radio-frequency reactive sputtering from a Cd-In alloy target. Theoretically, it is proposed that three types of point defects play the most important role in affecting the carrier concentration and the scattering of conduction electrons, namely, oxygen vacancies, impure point defects and dissolved surplus oxygen trap centers. At the same time, this dissertation formulated the effect of band-gap narrowing and Burstein-Moss(B-M) shift on optical band-gap.For preparing large area CIO films with low resistivity and high transmissivity, we studied the effect of oxygen density and substrate temperature on optical and electrical properties, respectively. By the measurement of Hall and Seebeck effects, the electrical parameters can be obtained, and the optical properties in ultraviolet, visible and infrared wave-band can be obtained by analyzing the optical spectrums of CIO films. A lot of experiments indicated that the band-gap narrowing greatly impact on optical band-gap. For obtaining correct optical band-gap, we use fitting method instead of extrapolation method. The experimental results show that a proper substrate temperature, namely Ts≈280℃ and oxygen density of 8%, should be used in sputtering for getting higher transmittance of light and conductivity.(2) Measurement of frequency response of high-speed photodetectorsUltra-wideband frequency response of high-speed photodetectors, such as GaAs and InGaAs optoelectronic diodes can be measured by utilizing the coherence of light (optical heterodyne technique). Experimentally, the double laser, single laser and amplified spontaneous emission techniques were used to measure frequency response respectively.In this dissertation, we mainly investigate the single laser technique for frequency response measurement and have a deep research for experiment-packaged three three-sections tunable distributed Bragg reflector (DBR) laser. In experiment, we research the optical spectrum and analyze the influence of driven current noise on optical spectrum linewidth of tunable DBR laser. The accurate photodetectors response can be obtained by calibrating the actually measured result according to linewidth and spectrum power. The experimental results prove that these means are effective and easy to carry out. In other one method for measuring response by using amplified spontaneous emission techniques, we study the effect of three kinds of interferometers on measurement dynamic range. Experiment show that using the delayed fiber ring interferometer in measurement system can obtain maximum measurement sensitivity.