硅衬底Ba1-xSrxNbyTi1-yO3薄膜光敏特性的研究

利用硅平面工艺和氩离子束镀膜技术在SiO2/Si衬底上淀积一层厚45nm的钛铌酸锶钡(Ba1-xSrxNbyTi1-yO3)薄膜，制成Al/Ba1-xSrxNbyTi1-yO3/SiO2/Si结构平面型薄膜电阻器。测试了该薄膜电阻器的吸收光谱，不同照度、电压下的光电流，调制光下的频率特性。实验结果表明：在钛酸钡中掺入锶(Sr)和铌(Nb)后，禁带内引入了杂质能级，钛铌酸锶钡禁带宽度变为2.7eV，且可见光区域存在连续的吸收峰。该薄膜在近紫外及可见光范围内具有良好的光敏特性，其灵敏度和光电导增益较高，并且具有较好的线性光照特性。光照强度较低时，电阻器的光照特性属于单分子复合过程；光照强度较高时，电阻器的光照特性属于双分子复合过程。通过对该薄膜电阻器频率特性的测量得出：在光照度为200lx时，薄膜中光生载流子的寿命为27ms。

A Study on Photosensitivity Characteristics of Ba1-xSrxNbyTi1-yO3 Thin Film on SiO2/Si Substrate

Ba_(1-x)Sr_xNb_yTi_(1-y)O_3 thin film (45nm) deposited on a SiO_2/Si substrate by the argon ion-beam sputtering technique is employed to fabricate planar thin-films resistors used in the IC standard technology.The absorption spectra of the Ba_(1-x)Sr_xNb_yTi_(1-y)O_3 thin films, the photocurrent under different illumination and voltage, and the photocurrent-frequency characteristics of the film-resistors are studied.The experimental results show that Sr and Nb doped in BaTiO_3 produce the impurity energy level in forbidden gap. Therefore,the energy gap drops down to 2.7eV and there are some consecutive absorption peaks in the visible region. The film has good photobehavior in the range from near ultraviolet to visible light, and it has high photosensitivity, high photoconductive gain and high linear illumination performance. While the illumination intensity is weak, the variaion of the current will be large, which is called one-center recombination process; while the illuminaion is strong, the variation will be smooth and more linear, which is called two-center recombination process.In this paper, the frequency response of the Ba_(1-x)Sr_xNb_yTi_(1-y)O_3 thin-film resistor is investigated. The lifetime of optically excited carriers is 27ms at 200Lux.