| 题名 | LiAlO2、LiGaO2晶体的生长及其上ZnO薄膜制备研究 |
| 作者 | 黄涛华 |
| 学位类别 | 博士 |
| 答辩日期 | 2008 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 周圣明 |
| 关键词 | LiAlO2 LiGaO2 ZnO 晶体生长 MOCVD 磁控溅射 |
| 其他题名 | Growth of LiAlO2, LiGaO2 crystals and deposition of ZnO films on these substrates |
| 中文摘要 | 近年来，以GaN和ZnO为代表的宽禁带半导体材料以其优越的性质和广阔的应用前景获得了越来越多的关注，它们在光电器件、大功率、高温电子器件等方面展现出巨大的潜力。LiAlO2和LiGaO2作为它们很有前景的衬底也受到了广泛的关注，但是这两种衬底晶体生长困难限制了其应用。本论文系统研究了LiAlO2和LiGaO2晶体的生长，并在衬底上进行了ZnO薄膜的生长。论文主要包括以下几个方面的内容： 1．在前有基础上，采用中频感应提拉法生长了LiAlO2晶体，通过建立合适的温场后，很好地抑制了晶体生长中Li2O的挥发，在优化各种工艺参数后，成功地生长了直径为2inch完整的、高质量的LiAlO2晶体，而且工艺具有很好的重复性。(100) LiAlO2的X射线四晶摇摆曲线半高宽最小仅为17.7arcsec，这是目前为止报道的最小值，位错密度也只有3.0×103 cm-2，晶体在可见及红外波段具有高的透过率，其红外波段的截止波长为6.7 μm。在生长装置中采用更大的铱坩埚及铱后热器后，优化工艺生长的LiAlO2晶体具有更大的尺寸及更高的质量，而且降温时间也大为缩短了。 2．采用中频感应提拉法生长了LiGaO2晶体，探索出了提拉法生长此晶体的合适温场条件、工艺参数，生长中的挥发几乎被完全抑制，成功生长了完整、透明的高质量LiGaO2晶体。(001) LiGaO2的X射线四晶摇摆曲线半高宽仅为16.2arcsec，这也是目前为止报道的最小值；LiGaO2 (001) 、(100)和(010)面的位错密度均低于104 cm-2。 3．采用金属有机化学气相沉积（MOCVD）和磁控溅射法在LiAlO2(100)面上制备了ZnO薄膜。用MOCVD方法获得了单一取向的非极性m面ZnO薄膜，(1100)峰半高宽为0.79°；利用原子力显微镜在薄膜上观察到了明显的长方形晶粒；偏振透射光谱、偏振拉曼光谱表明(1100)ZnO薄膜在面内是各向异性的。而磁控溅射法获得的则是混合取向的多晶ZnO薄膜，随衬底温度升高，(1100)峰的相对强度有所增强，不同温度下薄膜的形貌差异较大；样品的拉曼光谱中都出现E1（LO）振动模式，表明存在较多的氧空位、间隙锌等缺陷。 4．采用磁控溅射法在LiGaO2(001)面在不同温度下生长了ZnO薄膜，所有的ZnO薄膜均为高度c轴择优取向，薄膜内均存在着压应力。当衬底温度为200-600℃时，出现了较强的紫外发射峰，而可见光发射峰几乎看不到，其中600℃生长的薄膜的紫外发射峰最强，峰半高宽也是最小的，约为140meV；在800℃生长的ZnO薄膜其PL谱上有一个很强的绿光发射峰。 5．采用磁控溅射法在600℃相同的条件下在LiGaO2(001)、(100)、(010)衬底上生长了ZnO薄膜，薄膜的择优取向分别为[0001]、[1100] 、[1120]，其形貌差异很大，其中(0001) ZnO薄膜呈现出明显的六方柱状晶粒，(1100)取向的薄膜内的晶粒尺寸最大。从这三个不同取向的ZnO薄膜的PL谱上几乎未看到可见光发射峰，其中(1100)薄膜具有最强的紫外发射峰和最小的峰半高宽。 |
| 英文摘要 | In recent years, Wide Band Gap (WBG) semiconductors such as GaN and ZnO have received more and more attention due to their superior properties and potential applications in photoelectric devices, high power and high temperature electronic devices. Much attention has also been paid to LiAlO2 and LiGaO2 crystals because they can be used as the substrates of GaN and ZnO. However, the difficulty in growing the two crystals has hampered their applications. In this paper, the Czochralski growth of LiAlO2 and LiGaO2 crystals were studied, and ZnO films were fabricated on the substrates. Results obtained are described as follows: 1. LiAlO2 crystal has been grown by Czochralski method. The evaporation of Li2O has been controlled by establishing a suitable temperature field in the furnace. After optimizing the growth procedure, we can reproducibly obtain large size (2 inch) and high quality LiAlO2 crystals. The full width at half maximum (FWHM) of the rocking curve for LiAlO2 (100) slice is only 17.7 arcsec, which is the smallest among the reported values at present. The overall dislocation density is only about 3.0×10 3 cm-2. The crystal shows high transmittance in visible and IR region, and the cutoff wavelength in infrared region is 6.7 μm. When we used a bigger iridium and an iridium afterheater, the quality of as-grown crystal has been further improved. The cooling time has also been greatly shortened. 2. High quality LiGaO2 crystal has been grown by Czochralski method. The volatilization during the crystal growth has almost been completely suppressed by decreasing the axial temperature gradient and optimizing the growth procedure. The FWHM of LiGaO2 (001) slice is only 16.2 arcsec which is also the smallest among the reported values. The dislocation densities on (001), (100) and (010) planes are all less than 10 4/cm2. 3. ZnO films were grown on LiAlO2 (100) substrate by MOCVD and magnetron sputtering, respectively. The ZnO film fabricated by MOCVD is (1100)(m-plane) oriented. The FWHM of (1100) ZnO film is 0.79°. Grains with rectangular shape are observed in m-plane ZnO film by AFM. The polarized absorption spectra and the polarized Raman spectra show that the film is anisotropy in plane. However, the ZnO films fabricated by magnetron sputtering have not obvious preferred orientation. With the increase of growth temperature, the relative intensity of peak increases. All films show different morphologies. The E1 (LO) mode is observed in the Raman spectra of all ZnO films. 4. ZnO films were grown on LiGaO2 (001) by RF magnetron sputtering. All ZnO films have highly c-axis preferred orientation. The stresses in the films are compressive. All ZnO films show a typical near-band-edge (NBE) UV emission peak. The UV peak of ZnO film grown at 600℃ shows the highest intensity with the smallest FWHM of 140meV. For the ZnO film fabricated at 800℃, a strong deep-level emission is observed. 5. ZnO films were fabricated on LiGaO2 (001), (100) and (010) planes by RF magnetron sputtering in the same condition. It is found that the orientation of ZnO films is strongly dependent on the substrate plane. [0001],[1100] and [1120] oriented ZnO films are obtained on LiGaO2 (001), (100) and (010), respectively. The ZnO films with different orientations show different morphologies. Well-aligned hexagonal columnar grains in the (0001) ZnO film are clearly observed. All ZnO films show a typical near-band-edge UV emission peak at about 378 nm (3.27eV), and no visible emission is observed. The UV peak of (1100) ZnO film shows the highest intensity with the smallest FWHM of 135meV. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15599]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 黄涛华. LiAlO2、LiGaO2晶体的生长及其上ZnO薄膜制备研究[D]. 中国科学院上海光学精密机械研究所. 2008. |
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