基于绝缘层中载流子碰撞离化的氧化锌基日盲雪崩探测器研究

Zinc oxide (ZnO) based solar-blind ultraviolet avalanche photodetectors have a variety of potential applications, but the challenging issue of p-type doping makes the realization of common p-i-n structured ZnO-based avalanche photodetectors almost impossible. Aiming at this topic, we propose that by taking advantage of the carrier-multiplication caused by impact ionization process occurred in an insulation layer under a relatively large electric field, ZnO-based avalanche photodetectors operating in solar-blind ultraviolet spectrum region may be realized. With such assumption, Au/MgO/MgZnO:Ga/MgO/Au structures will be designed and constructed experimentally. In these structures, ultraviolet photons whose energy is larger than the bandgap of the MgZnO layer will be absorbed by this gallium doped low-resistance MgZnO layer, then free carriers will be generated in this layer. These photogenerated carriers will be drifted to the corresponding electrodes by the applied bias, and they have to tunnel through the MgO layer. They will be accellerated greatly by the strong electric field in the MgO layer when enter this layer. These energetic carriers will impact with the lattice of the MgO layer to release their energy and excite more free carriers in the MgO layer. The newly excited carrers will again gain much kinetic energy given by the strong electric field, and impact again with the lattice of the MgO to produce more carriers. In this way, carrier multiplication occurs in the MgO layer. The multiplicated carriers will be separated by the bias voltage, and collected by the electrodes to serve for the photoresponse of the photodetector. In this way, ZnO-based solar-blind ultraviolet avalanche photodetectors will be achieved. The idea proposed in this project may provide an alternative promising route to ZnO-based solar-blind ultraviolet avalanche photodetectors by bypassing the challenging issue of p-type doping of ZnO-based materials.

氧化锌(ZnO)基日盲雪崩探测器在诸多方面有广泛的潜在应用，但目前ZnO的p型掺杂问题尚未完全解决，使得基于p-i-n结构的ZnO基雪崩探测器难以实现。针对上述问题，本项目中我们提出利用较高电场下MgO绝缘层内会通过碰撞离化产生载流子倍增的原理来实现ZnO基日盲雪崩探测器，实验上拟设计并构建Au/MgO/MgZnO:Ga/MgO/Au结构。该结构中，禁带宽度位于日盲波段的低电阻率MgZnO层吸收光子产生光生载流子，这些载流子在电场驱动下进入MgO中，并被该层中较高的电场加速。这些被加速的载流子会与MgO晶格碰撞而在MgO中激发出新的载流子，该新的载流子又会被MgO中的电场加速，并再次与MgO的晶格碰撞而产生载流子的倍增。这些倍增的载流子被电场分离从而实现ZnO基日盲紫外雪崩探测器。该方案规避了ZnO p型掺杂尚不成熟的难题，有望为ZnO基日盲雪崩探测器的实现提供新的可行途径。

工作在日盲波段（220- 280 nm）的紫外探测器由于没有了太阳这一地球上最大辐射源的干扰，具有背景干扰小、目标信号容易探测、不易产生虚警等优点，因而在对于虚警率要求极高的军事领域如超高速飞行器火箭或导弹的预警和探测有广泛应用前景。 近年来基于宽禁带半导体如氧镁锌、铝镓氮、氧化镓、金刚石等的日盲探测器因其体积小、能耗低、无需冷却等优点因而成为近年研究的热点。但是，如何实现日盲波段的高性能探测器依然是一个艰巨的挑战。本项目中我们提出利用绝缘层在较高电场下也可以发生载流子与晶格的碰撞离化从而产生载流子倍增来实现日盲紫外雪崩探测器的思想，实验上构建了Au/MgO/ZnO/MgO/Au结构，并在该结构中实现了ZnO基雪崩探测器，被同行在综述性论文中评论为“第一次实现了氧化锌基雪崩探测器”，及“可能为高性能ZnO基紫外探测器的实现提供一条可行途径”等。另外，我们提出以禁带宽度位于日盲波段的氧化镓作为工作介质，20V偏压下实现了响应度为17 A/W，量子效率达8228%，探测度为7.0× 10^12 Jones，暗电流为6.2× 10-10 A的日盲探测器。我们还利用碳点和氧化锌量子点复合，实现了探测度和噪声等效功率分别为3.1× 10^17 cmHz1/2/W和7.8×10^-20 W的ZnO基紫外探测器。在本项目资助下，项目组人员共发表SCI论文31篇，其中影响因子大于3.0的26篇。项目负责人获得国家杰出青年基金、中组部万人计划青年拔尖人才、人力资源与社会保障部百千万人才工程、长春市有突出贡献专家等荣誉称号，中科院百人计划终期评估中获得“优秀“。培养博士生6名，硕士生2名。团队获吉林省自然科学一等奖1项。