纳米金刚石薄膜紫外探测器研究

Development of Ultraviolet Photodetector with Nano-Diamond Films

利用微波等离子体化学气相沉积(MPCVD)技术,制备了高表面光洁度(其表面的高度标准偏差约为8.6nm)的纳米金刚石薄膜,在其表面上制作了共平面MSM结构的紫外探测器。电荷-深能级瞬态谱(Q-DLTS)测试表明,纳米金刚石薄膜的带隙中引入了一个能级,能级激活能E_a=0.134eV,俘获截面σ_s=2.81×10^(-22)cm^2,能级密度N_I～10^(12)cm^(-2)。利用脉冲氙灯作为光源对器件的紫外探测性能进行了测试,器件在10V偏压下的脉冲光电流峰值可达9μA,光电流的响应时间为ms量级。分析得出,纳米金刚石薄膜中存在的这个浅能级,由于其低的激活能和小的俘获截面起到非平衡载流子的陷阱作用,导致紫外探测器具有较慢的响应速度和较高的光电流。

A Schottky type,coplanar,metal-semiconductor-metal(MSM) structured,ultraviolet(UV) photo-detector was developed with the highly smooth,nano-crystalline diamond films(NDF),grown by microwave plasma chemical vapor deposition(MPCVD) on Si(100) substrates.The microstructures and properties of the nano-diamond films were characterized with X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and charge-based deep level transient spectroscopy(Q-DLTS).The results show that a trapping center with an activation energy,E_a=0.134eV,an energy density,N_t～10^(12) cm^(-2),and a capture cross section,σ_s=2.81×10^(-22)cm^2,was introduced into the nano-diamond films.In the test with a pulsed xenon lamp,a photocurrent up to 9μA,at a bias of 10V and a response time of a few ms, was obtained.The possible mechanism is that the shallow level may serve as the trapping center rather than recombination center because the low activation energy and the small capture section result in the slow response and high photocurrent.