基于含三价稀土离子的氧化物薄膜的硅基电致发光器件
发布时间：2018-07-28 18:15
【摘要】：众所周知,作为微电子工业基础材料的硅是一种间接带隙半导体,发光效率非常低,这严重限制了硅基光电集成技术的发展。因此,需要利用其它发光材料制备用于硅基光电集成的光源。稀土离子具有特殊的电子结构,其发光具有色纯度高、稳定性好、受基体和外界环境影响小等特点,这使得人们以很大的热情研究稀土离子发光。稀土离子的有效激发通常需要适当的基体材料,而氧化物便是相当理想的基体材料,其中包括氧化物半导体。稀土掺杂的氧化物薄膜的制备工艺与集成电路制造工艺相兼容,因此,实现硅基稀土掺杂氧化物薄膜电致发光器件,对于拓宽稀土离子发光的应用范围和发展硅基光电集成所需的光源具有重要意义。本文详细研究了以掺入不同稀土离子的TiO2薄膜为发光层的硅基发光器件的电致发光及其物理机制。此外,还制备了禁带宽度相对较小(属于半导体范畴)的Tb4O7薄膜为发光层的MOS器件,实现了Tb3+离子的特征电致发光。本文取得的主要创新成果如下：(1)利用射频溅射法,在重掺p型硅片(p+-Si)上沉积Eu含量不同(0.8%和1.2%)的TiO2 (TiO2:Eu)薄膜,随后进行550或650 ℃的热处理。在此基础上,制备了基于TiO2:Eu/p+-Si异质结的器件,实现其电致发光。研究发现,与Eu3+相关的红色发光是由TiO2基体中的氧空位作为敏化中心向邻近的Eu3+离子传递的能量所激发的,而该过程减弱了与氧空位相关的可见发光。TiO2薄膜中更高的Eu含量和TiO2:Eu薄膜的更高热处理温度均能够促进从TiO2基体向Eu3+离子的能量传递。因此,通过提高TiO2薄膜中的Eu含量和TiO2：Eu薄膜的热处理温度,可以使器件的电致发光从氧空位相关的发光为主转变为与Eu相关的发光为主,从而展现出不同的发光颜色。(2)利用射频溅射法,在p+-Si上沉积不同Tm含量的TiO2薄膜,随后进行氧气氛下650℃热处理。在此基础上,制备基于TiO2:Tm/p+-Si异质结的器件,实现了源自TiO2基体的可见发光和源自Tm3+离子的近红外电致发光。研究发现,基于TiO2：Tm(0.9%)薄膜的器件发射出与Tm3+离子相关的～800 nm发光,同时与TiO2基体相关的可见发光显著减弱,表明与Tm3+相关的发光是由TiO2基体向Tm3+离子传递的能量激发的。随着TiO2：Tm薄膜中的Tm含量的增加,上述可见和近红外发光均显著增强,可归因于掺入更高含量的Tm3+在TiO2基体中引入了更多氧空位。此外,在TiO2:Tm(1.6%)薄膜中共掺F后,器件的可见和近红外发光被完全抑制。由于离子半径相近,掺入的F-离子倾向于占据氧空位的位置。这从侧面证实了TiO2基体与Tm3+离子之间的能量传递是通过氧空位作为敏化中心进行的。(3)利用射频溅射法,在p+-Si上沉积共掺Fe和Er的Ti02[Ti02:(Fe,Er)]薄膜,随后进行氧气氛下550℃热处理。在此基础上,制备了基于Ti02:(Fe, Er)/p+一Si异质结的器件。在正向偏压下,该器件仅发射出与Er3+离子相关的～1540nm近红外光。研究表明,共掺Fe抑制了与Er3+离子和TiO2基体中的氧空位相关的可见发光,而与Er3+离子相关的～1540 nm发光被一定程度地增强。Fe杂质在TiO2禁带中引入能级,作为电子和空穴的复合中心。载流子通过与Fe相关的能级辅助的间接复合所释放的能量仅能激发电子从Er3+离子的基态跃迁到次低的激发态,在随后的退激发过程中,仅发射出～1540 nm的近红外发光。(4)在重掺n型硅片(n+-Si)上先通过干法热氧化形成～10 nm的SiO2薄膜,然后利用射频溅射法沉积掺入不同稀土离子的TiO2(TiO2:RE,RE=Eu、Er、Tm或Nd)薄膜,随后进行氧气氛下700℃热处理。在此基础上,制备了ITO/TiO2:RE/SiO2/Si结构的器件。在低于10 V的直流偏压下,实现了该类器件的红色、绿色、蓝色和近红外的电致发光,它们源自于TiO2薄膜中的各种稀土离子受碰撞激发后的自发辐射。分析指出,当在ITO电极上施加足够高的正向电压时,n+-Si中的电子通过缺陷辅助隧穿机制进入SiO2层的导带,在电场驱动下,电子落入Ti02：RE层的导带,获得了相当于SiO2与TiO2导带势能差的能量(～4 eV),从而成为热电子。这些热电子碰撞激发TiO2薄膜中的RE3+离子,从而导致RE3+离子的特征发光。(5)利用射频溅射法,分别在重掺磷和重掺硼的硅衬底(n+-Si和p+-Si)上沉积Tb4O7薄膜,随后进行氩气氛下900℃热处理。在此基础上,制备以Tb4O7薄膜为发光层的MOS器件,实现了源自Tb3+离子内4f跃迁的绿色电致发光,其开启电压低于10 V。通过分析器件的电流-电压特性和电致发光谱,指出n+-Si(或p+～Si)中的电子(空穴)通过缺陷辅助隧穿机制进入Tb4O7的导带(价带),并在电场作用下加速,形成热电子(空穴),它们碰撞激发Tb4O7薄膜中固有的Tb3+离子,从而导致Tb3+离子的特征绿色发光。
[Abstract]:It is well known that silicon, an indirect band gap semiconductor, is an indirect band gap semiconductor with low luminescence efficiency, which seriously restricts the development of silicon based photoelectric integration technology. Therefore, other luminescent materials need to be used to prepare light sources for silicon based photoelectric integration. Rare earth ions have special electronic structures and their luminescence has color purity. It is characterized by high stability and small influence on the matrix and the external environment. This makes people study the luminescence of rare earth ions with great enthusiasm. The effective excitation of rare earth ions usually requires appropriate matrix material, and oxide is quite ideal matrix material, including oxide semiconductor. Therefore, the realization of silicon based rare earth doped oxide thin film electroluminescent devices is of great significance for widening the application range of rare earth ion luminescence and developing the light source required for silicon based photoelectric integration. In this paper, the silicon based luminescence of TiO2 films doped with different rare earth ions as the luminescent layer is studied in detail. The electroluminescence and the physical mechanism of the device are also made. In addition, the Tb4O7 thin film with a relatively small gap (belonging to the semiconductor category) is also prepared as the MOS device of the luminescent layer, and the characteristic electroluminescence of the Tb3+ ions is realized. The main achievements of this paper are as follows: (1) the content of Eu in the heavily doped P silicon wafer (p+-Si) is not deposited by radio frequency sputtering. The TiO2 (TiO2:Eu) film (0.8% and 1.2%) was followed by heat treatment at 550 or 650 C. On this basis, a device based on TiO2:Eu/p+-Si heterojunction was prepared to realize its electroluminescence. It was found that the red luminescence related to Eu3+ was excited by the oxygen vacancy in the TiO2 matrix as the energy transfer from the sensitization center to the adjacent Eu3+ ion. This process reduces the higher Eu content in the visible luminescent.TiO2 film related to the oxygen vacancy and the higher heat treatment temperature of the TiO2:Eu film, which can promote the energy transfer from the TiO2 matrix to the Eu3+ ion. Therefore, the electroluminescence of the device can be induced by increasing the Eu content in the TiO2 film and the heat treatment temperature of the TiO2:Eu film. The oxygen vacancy related luminescence mainly changed to Eu related luminescence, which showed different luminescence colors. (2) TiO2 films with different Tm content were deposited on p+-Si by radio frequency sputtering and then heated at 650 C under oxygen atmosphere. On this basis, the devices based on TiO2:Tm/p+-Si heterojunction were prepared, and the TiO2 matrix was realized. The visible luminescence and near infrared electroluminescence derived from Tm3+ ions have been found. It is found that the devices based on TiO2:Tm (0.9%) films emit a 800 nm luminescence associated with Tm3+ ions, while the visible luminescence associated with the TiO2 matrix decreases significantly, indicating that the luminescence related to the Tm3+ is excited by the energy transferred from the TiO2 matrix to the Tm3+ ions. The increase in the content of Tm in the 2:Tm film is significantly enhanced by the visible and near infrared luminescence, which is attributable to the introduction of more oxygen vacancies in the TiO2 matrix with a higher content of Tm3+. In addition, the visible and near infrared luminescence of the TiO2:Tm (1.6%) thin film is completely suppressed after the incorporation of F in the TiO2:Tm film. As the ionic radius is similar, the doping of F- ions tilting. It is confirmed that the energy transfer between the TiO2 matrix and the Tm3+ ion is carried out by the oxygen vacancy as the sensitization center. (3) the Ti02[Ti02: (Fe, Er) Film Co doped with Fe and Er (Fe, Er)) is deposited on p+-Si by radio frequency sputtering, then the heat treatment at 550 C under the oxygen atmosphere. On this basis, the preparation of Ti0 is made. 2: (Fe, Er) /p+ Si heterojunction devices. Under positive bias, the device only emits the near infrared light to 1540nm related to Er3+ ions. The study shows that the co doping of Fe inhibits the visible luminescence associated with the oxygen vacancy in the Er3+ ions and TiO2 matrix, and the ~ 1540 nm luminescence related to the Er3+ ion is enhanced to a certain extent. The energy level is introduced in the band as the compound center of the electrons and holes. The energy released by the carrier assisted indirect recombination with the Fe related energy level can only stimulate the electron transition from the base state of the Er3+ ion to the sub low excited state. In the subsequent deactivation process, the emission of near infrared luminescence to 1540 nm is only emitted. (4) the N type silicon wafer (n+-Si) is heavily doped. The SiO2 thin film to 10 nm was formed by dry thermal oxidation, and then the TiO2 (TiO2:RE, RE=Eu, Er, Tm or Nd) films doped with different rare earth ions were deposited by radio frequency sputtering, then the heat treated at 700 C under oxygen atmosphere. On this basis, the ITO/TiO2:RE/SiO2/Si junction device was prepared. Under the DC bias of less than 10 V, this kind of device was realized. The red, green, blue and near infrared electroluminescence of the devices originate from the spontaneous emission of various rare earth ions in the TiO2 film after collisions. It is pointed out that when the positive voltage is high enough on the ITO electrode, the electrons in n+-Si enter the conduction band of the SiO2 layer through the defect assisted tunneling mechanism, and the electric field is driven by the electric field. The conduction band falling into the Ti02:RE layer obtained the energy equivalent to the potential energy difference between SiO2 and TiO2 (~ 4 eV) and became hot electrons. These thermo electron collisions stimulated the RE3+ ions in the TiO2 film, resulting in the characteristic luminescence of the RE3+ ions. (5) the deposition of phosphorus and boron doped silicon substrates (n+-Si and p+-Si) by radio frequency sputtering. Tb4O7 film is then heated at 900 C in argon atmosphere. On this basis, a MOS device with a Tb4O7 film as a luminescent layer is prepared, and the green electroluminescence from the 4f transition in the Tb3+ ion is realized. The opening voltage is lower than 10 V. through the current voltage characteristic and electroluminescence spectrum of the analysis device, and the electron (hole) in n+-Si (or p+ to Si) is pointed out. Through the defect assisted tunneling mechanism, the conduction band (valence band) of Tb4O7 is entered, and the thermal electrons (holes) are formed under the action of the electric field. They collide and stimulate the inherent Tb3+ ions in the Tb4O7 film, which leads to the characteristic green luminescence of the Tb3+ ions.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN383.1;TB383.2
，
本文编号：2151191
[Abstract]:It is well known that silicon, an indirect band gap semiconductor, is an indirect band gap semiconductor with low luminescence efficiency, which seriously restricts the development of silicon based photoelectric integration technology. Therefore, other luminescent materials need to be used to prepare light sources for silicon based photoelectric integration. Rare earth ions have special electronic structures and their luminescence has color purity. It is characterized by high stability and small influence on the matrix and the external environment. This makes people study the luminescence of rare earth ions with great enthusiasm. The effective excitation of rare earth ions usually requires appropriate matrix material, and oxide is quite ideal matrix material, including oxide semiconductor. Therefore, the realization of silicon based rare earth doped oxide thin film electroluminescent devices is of great significance for widening the application range of rare earth ion luminescence and developing the light source required for silicon based photoelectric integration. In this paper, the silicon based luminescence of TiO2 films doped with different rare earth ions as the luminescent layer is studied in detail. The electroluminescence and the physical mechanism of the device are also made. In addition, the Tb4O7 thin film with a relatively small gap (belonging to the semiconductor category) is also prepared as the MOS device of the luminescent layer, and the characteristic electroluminescence of the Tb3+ ions is realized. The main achievements of this paper are as follows: (1) the content of Eu in the heavily doped P silicon wafer (p+-Si) is not deposited by radio frequency sputtering. The TiO2 (TiO2:Eu) film (0.8% and 1.2%) was followed by heat treatment at 550 or 650 C. On this basis, a device based on TiO2:Eu/p+-Si heterojunction was prepared to realize its electroluminescence. It was found that the red luminescence related to Eu3+ was excited by the oxygen vacancy in the TiO2 matrix as the energy transfer from the sensitization center to the adjacent Eu3+ ion. This process reduces the higher Eu content in the visible luminescent.TiO2 film related to the oxygen vacancy and the higher heat treatment temperature of the TiO2:Eu film, which can promote the energy transfer from the TiO2 matrix to the Eu3+ ion. Therefore, the electroluminescence of the device can be induced by increasing the Eu content in the TiO2 film and the heat treatment temperature of the TiO2:Eu film. The oxygen vacancy related luminescence mainly changed to Eu related luminescence, which showed different luminescence colors. (2) TiO2 films with different Tm content were deposited on p+-Si by radio frequency sputtering and then heated at 650 C under oxygen atmosphere. On this basis, the devices based on TiO2:Tm/p+-Si heterojunction were prepared, and the TiO2 matrix was realized. The visible luminescence and near infrared electroluminescence derived from Tm3+ ions have been found. It is found that the devices based on TiO2:Tm (0.9%) films emit a 800 nm luminescence associated with Tm3+ ions, while the visible luminescence associated with the TiO2 matrix decreases significantly, indicating that the luminescence related to the Tm3+ is excited by the energy transferred from the TiO2 matrix to the Tm3+ ions. The increase in the content of Tm in the 2:Tm film is significantly enhanced by the visible and near infrared luminescence, which is attributable to the introduction of more oxygen vacancies in the TiO2 matrix with a higher content of Tm3+. In addition, the visible and near infrared luminescence of the TiO2:Tm (1.6%) thin film is completely suppressed after the incorporation of F in the TiO2:Tm film. As the ionic radius is similar, the doping of F- ions tilting. It is confirmed that the energy transfer between the TiO2 matrix and the Tm3+ ion is carried out by the oxygen vacancy as the sensitization center. (3) the Ti02[Ti02: (Fe, Er) Film Co doped with Fe and Er (Fe, Er)) is deposited on p+-Si by radio frequency sputtering, then the heat treatment at 550 C under the oxygen atmosphere. On this basis, the preparation of Ti0 is made. 2: (Fe, Er) /p+ Si heterojunction devices. Under positive bias, the device only emits the near infrared light to 1540nm related to Er3+ ions. The study shows that the co doping of Fe inhibits the visible luminescence associated with the oxygen vacancy in the Er3+ ions and TiO2 matrix, and the ~ 1540 nm luminescence related to the Er3+ ion is enhanced to a certain extent. The energy level is introduced in the band as the compound center of the electrons and holes. The energy released by the carrier assisted indirect recombination with the Fe related energy level can only stimulate the electron transition from the base state of the Er3+ ion to the sub low excited state. In the subsequent deactivation process, the emission of near infrared luminescence to 1540 nm is only emitted. (4) the N type silicon wafer (n+-Si) is heavily doped. The SiO2 thin film to 10 nm was formed by dry thermal oxidation, and then the TiO2 (TiO2:RE, RE=Eu, Er, Tm or Nd) films doped with different rare earth ions were deposited by radio frequency sputtering, then the heat treated at 700 C under oxygen atmosphere. On this basis, the ITO/TiO2:RE/SiO2/Si junction device was prepared. Under the DC bias of less than 10 V, this kind of device was realized. The red, green, blue and near infrared electroluminescence of the devices originate from the spontaneous emission of various rare earth ions in the TiO2 film after collisions. It is pointed out that when the positive voltage is high enough on the ITO electrode, the electrons in n+-Si enter the conduction band of the SiO2 layer through the defect assisted tunneling mechanism, and the electric field is driven by the electric field. The conduction band falling into the Ti02:RE layer obtained the energy equivalent to the potential energy difference between SiO2 and TiO2 (~ 4 eV) and became hot electrons. These thermo electron collisions stimulated the RE3+ ions in the TiO2 film, resulting in the characteristic luminescence of the RE3+ ions. (5) the deposition of phosphorus and boron doped silicon substrates (n+-Si and p+-Si) by radio frequency sputtering. Tb4O7 film is then heated at 900 C in argon atmosphere. On this basis, a MOS device with a Tb4O7 film as a luminescent layer is prepared, and the green electroluminescence from the 4f transition in the Tb3+ ion is realized. The opening voltage is lower than 10 V. through the current voltage characteristic and electroluminescence spectrum of the analysis device, and the electron (hole) in n+-Si (or p+ to Si) is pointed out. Through the defect assisted tunneling mechanism, the conduction band (valence band) of Tb4O7 is entered, and the thermal electrons (holes) are formed under the action of the electric field. They collide and stimulate the inherent Tb3+ ions in the Tb4O7 film, which leads to the characteristic green luminescence of the Tb3+ ions.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN383.1;TB383.2
，
本文编号：2151191
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