【作者】 张银珠；

【导师】 叶志镇；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2006， 博士

【摘要】 ZnO是一种直接带隙宽禁带Ⅱ-Ⅵ族化合物半导体材料,其晶体结构、晶格常数和禁带宽度都与GaN非常接近。ZnO最大的优势在于它的激子束缚能很大,约为60meV,是GaN激子束缚能的两倍多,可以在室温或更高温度下实现激子受激发光。因此,ZnO在短波长光电器件领域有着巨大的应用潜力。 本文利用自行设计建立的脉冲激光沉积（PLD）系统,进行了Zn_1-xMg_xO合金薄膜和ZnO/Zn_1-xMg_xO多层异质结构的生长、p型Zn_1-xMg_xO薄膜的初步探索以及p型ZnO薄膜的掺杂研究,并研制了一个硅基ZnO光电导型紫外探测器。研究硅基ZnO/Zn_1-xMg_xO多层异质结构和量子阱结构的结晶质量和发光特性,为ZnO光电器件的研发奠定基础。而Zn_1-xMg_xO薄膜p型转变的成功能为ZnO异质p-n结器件做好材料准备。本文采用一种新的共掺技术——Li-N双受主共掺,成功制备了低电阻率的p-ZnO薄膜。 1.硅基Zn_1-xMg_xO合金薄膜及ZnO/Zn_1-xMg_xO异质结和量子阱结构 利用自制PLD系统在p-Si（100）上生长Zn_1-xMg_xO合金薄膜。从生长参数对薄膜的结构、形貌和光学性能的对比研究中,找到可适用于硅基ZnO/Zn_1-xMg_xO异质结构生长的合金薄膜的优化工艺参数。优化条件下制得的薄膜晶体质量良好,均具有高度c轴择优取向性,其晶体结构与ZnO的一致,表面粗糙度约为1nm,与ZnO的晶格失配度仅为-0.35%。 首次采用PLD技术在Si（100）和ZnO/Si（100）上生长Zn_1-xMg_xO/ZnO/Zn_1-xMg_xO双异质结,得到了具有完全c轴择优取向的晶粒致密的多层异质结构。其室温PL谱中均可以观察到异质结中ZnO层位于～3.3eV的近带边发光,无明显的深能级缺陷发光,表明多层异质结构的结晶质量较高。在ZnO/Si（100）上还尝试生长了ZnO/Zn_1-xMg_xO多量子阱结构,所得的是多层纳米结构。 首次以Li为受主掺杂元素,实现了Zn_1-xMg_xO薄膜的p型转变,电阻率为10.1Ωcm,载流子浓度为2.45x10¹⁸cm^-3,迁移率为0.251cm²/Vs。这项工作还在继续系统研究中。更多还原

【Abstract】 ZnO is a Ⅱ-Ⅵ compound semiconductor with a direct wide band gap of 3.3 eV. Its crystal structure, lattice parameter and band gap are quite close to those of GaN. The most significant advantage of ZnO lies in its extremely large exciton binding energy, about 60 meV, over double than that of GaN, which allows stimulated excitonic emission at room temperature or even higher temperature. Therefore, ZnO is a potential candidate for applications in short-wave optoelectronic devices, such as bule/violet light emitting diodes and laser diodes.Zn_1-xMg_xO alloy thin films and ZnO/Zn_1-xMg_xO heterostructures on silicon, as well as p-type Zn_1-xMg_xO and ZnO thin films, were prepared by home-made pulsed laser deposition （PLD）. In addition, a photoconductive ultraviolet detector based on ZnO films grown by PLD was fabricated on silicon. The crystalline quality and photoluminescent properties of the ZnO/Zn_1-xMg_xO heterostructures on silicon were investigated for exploiting ZnO-based optoelectronic devices. In this work, low resistivity p-type ZnO thin films were realized via a new kind of co-doping method, Li-N co-doping. 1. Zn_1-xMg_xO alloy thin films and ZnO/Zn_1-xMg_xO heterostructures on siliconHigh-quality Zn_1-xMg_xO alloy thin films with c-axis preferred orientation were grown on p-Si（100） by PLD. The alloy thin films had the same crystal structure with ZnO. The film prepared under optimized condition was highly crystalline, with a surface roughness of ¹ run and a small lattice mismatch with ZnO of -0.35%.ZnO/Zn_1-xMg_xO double heterostructures （DHs） were firstly fabricated on Si（lOO） and ZnO/Si（100） by PLD, respectively. The near band emission （-3.29 eV） from the ZnO layer in DHs was observed in the room-temperature photoluminescence sprectum. The deep level emission was quite weak, indicating high crystalline quality of the DHs. ZnO/Zn_1-xMg_xO multi-quantum wells （MQWs） with ten period were also firstly attempted to grow on ZnO/Si（100）.p-type Zn_1-xMg_xO thin films were firstly realized by PLD via Li mono-doping.The lowest resistivity was 10.1 Qcm, with a high hole concentration of 2.45xl018cm"3, and a Hall mobility of 0.251 cm2/Vs.2. Li* N double-acceptor codoping p-type ZnO thin filmsLow-resistivity p-type ZnO thin films were successfully fabricated by Li-N dual-acceptor doping method employing PLD. ZnO:Li ceramics with different Li content were used as Li agent and high-voltage ionized N2O was used as N source.Process parameters were optimized for Li-N codoping p-type ZnO thin films. The lowest resistivity of p-ZnO:（Li,N） thin films was 3.99 Qcm, with a high hole concentration of 9.12xl018cm3, and a Hall mobility of 0.172 cm2/Vs. The film was prepared at 450 °C with a pulsed laser fluence of 300 mJ, and a N2O pressure of 15 Pa with an ionizing power of 3.5 W. Li content in the target was 0.1 at%.There were four emission bands in 10 K PL spectrum of p-ZnO:（Li,N） thin film. The bands located at 3.374 eV, 3.318 eV, 3.215 eV and 3.154 eV, respectively, which were probably due to neutral acceptor bound exciton （A°X） and three donor-acceptor （DAP） transitions. The corresponding related acceptor levels of the three （DAP） transition were calculated to be -120 meV, -222 meV, and -283 meV, respectively. The levels located at -120 meV and -222 meV were assigned to Li acceptor and N acceptor respectively.Furthermore, physical mechanism of Li-N dual-acceptor doping was discussed and a co-doping model was proposed.3. ZnO photoconductive UV detector on siliconHigh-resistivity ZnO thin film with completely c-axis orientation was grown on Si（lll） by PLD. A photoconductive ultraviolet detector was fabricated based on this ZnO film with an M-S-M structure. Al was used as planar interdigital metal electrodes. The cutoff wavelength of Al-ZnO-Al ultraviolet detector was 370 nm, and its photoresponsivity was 0.5 A/W at 5 V bias.更多还原