摘要:
将纳米技术与传统的微电子工艺相结合,片上制备了横向结构氧化锌(ZnO)纳米线阵列紫外探测器件,纳米线由水热法直接自组织横向生长于叉指电极之间,再除去斜向的多余纳米线,其余工艺步骤与传统工艺相同。分别尝试了铬(Cr)和金(Au)两种金属电极的器件结构：由于Cr电极对其上纵向生长的纳米线有抑制作用,导致横向生长纳米线长度可到达对侧电极,光电响应方式为受表面氧离子吸附控制的光电导效应,光电流大但增益低,响应速度慢,经二次电极加固,纳米线根部与电极金属直接形成肖特基接触,光电响应方式变为光伏效应,增益和速度得到了极大改善；由于Au电极对其上纵向生长的纳米线有催化作用,导致溶质资源的竞争,相同时间内横向生长的纳米线不能到达对侧,而是交叉桥接,但却形成了紫外光诱导的纳米线间势垒结高度调控机理,得到的器件特性为最优,在波长为365 nm的20 mW/cm2紫外光照下,1 V电压时暗电流为10?9 A,光增益可达8×105,响应时间和恢复时间分别为1.1 s和1.3 s。
Abstract:
In this paper, we integrate nano technology into traditional microelectronic processing, and develop an on-chip UV sensor based on lateral growth ZnO nanowire arrays. Traditional procedures are used to fabricate the interdigital electrodes, and ZnO nanowires are self-organized and grown between electrodes laterally by hydrothermal method. Additional inclined nanowires are removed during the post-processing procedures, such as ultrasound cleansing and electrode reinforcement. Two kinds of electrode structures are applied, i.e. , Cr and Au. For the Cr electrode device structure, because Cr will restrain nanowires from growing vertically on its top, the laterally grown nanowire is long enough to reach the other side of the electrode. The corresponding photoelectric response mechanism is photoconduction controlled by surface oxide ion adsorption. Although the photocurrent is large, the gain is low, and the response speed is slow. Under the UV radiations of 20 mW/cm2 and of 365 nm in wavelength, the dark current is 2.2 × 10?4 A with 1 V bias voltage, the gain is up to 64, the photocurrent cannot reach saturation after 25 s, and the recovery time is 51.9 s. A secondary electrode can be fabricated after growing the nanowire arrays to reinforce the connection between the electrode and the ends of the nanowires. However, the direct contact between metal and semiconductor will form a Schottky contact. The photoelectric response mechanism is then changed to photovoltaic effect, which can greatly improve the gain and response speed. Under UV radiations of 20 mW/cm2 and of 365 nm in wavelength, the dark current is 4.3 × 10?8 A with 1 V bias voltage, the gain is up to 1300, the respond time is 3.8 s, and the recovery time is 5.7 s. For the Au electrode device structure, because Au is catalysis for ZnO nanowire growth, nanowires grown in lateral direction will compete with those grown in vertical direction, and hence the laterally grown nanowires are not long enough to reach the other side of the electrode. Nanowires grown from two sides of the electrodes will meet each other and form a bridging junction, however, this will turn the photoconduction mechanism from surface ion controlled into a bridging junction controlled, which yields the best device performance. Before removing the inclined nanowires by ultrasound cleansing, under UV radiations of 20 mW/cm2 and of 365 nm in wavelength, the dark current is 8.3 × 10?3 A with 1 V bias voltage, the gain is up to 1350, the respond time is 3.3 s, and the recovery time is 3.4 s. After removing the inclined nanowires, under UV radiations of 20 mW/cm2 and of 365 nm in wavelength, the dark current is 10?9 A with 1 V bias voltage, the gain is up to 8 × 105, the respond time is 1.1 s, and the recovery time is 1.3 s.
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