大面积可转移Beta-氧化镓单晶薄膜的制备及性质研究

Beta-gallium oxide with wide band-gap and high breakdown field can be made from lost-cost devices such as power devices with high breakdown voltage，deep ultraviolet optoelectronic devices and light emitting devices. Generally the growth substrates of beat-Ga2O3 have expensive cost, poor thermal and electrical conductivities. If the large-area (> 1 inch) epitaxial Ga2O3 single-crystalline thin films are exfoliated from their growth substrates, Ga2O3-based devices will draw much attention. The separation of nanoporous GaN two-layer and distributed Bragg reflector (DBR) thin films from sapphire substrates is easy. Based on such a realization, large-area and transferrable beta-Ga2O3 single-crystalline thin films grown on the nanoporous GaN thin films will be fabricated by metal-organic chemical vapor deposition (MOCVD) and post-annealing method. To obtain the optimum growth processing parameters of transferrable beta-Ga2O3 single-crystalline films, the structure and photoelectric properties which are influenced by the growth conditions such as doping concentration and growth temperature will be investigated systemically. The doped properties and mechanism of Sn-doped beta-Ga2O3 films will be evaluated systemically. Schottky barrier diodes (SBDs) of beta-Ga2O3 films will be fabricated as an example. The properties of SBDs such as breakdown voltage, ideality factors, and Schottky barrier height, which can be influenced by the growth conditions, will be discussed systemically. The photoelectric and photoluminescence properties and doping mechanism of beta-Ga2O3 films with rare earth elements will be evaluated systemically. Light emitting devices (LEDs) of beta-Ga2O3 thin films with rare earth elements will be fabricated. The properties of LEDs such as I-V and electroluminescence, which can be influenced by the growth condtions, will be studied systemically. The beta-Ga2O3 single-crystalline films can be transferred to multiple platforms, so this project will be helpful to the research and development of beta-Ga2O3 based devices as well as the integration of them and other photoelectric devices, and provides theory basis and experimental data for their applications.

具有宽带隙、高击穿电场的单晶Beta-氧化镓可制造耐高压功率器件、深紫外光电器件和发光器件。由于生长衬底价格昂贵和导热导电能力差，因此若实现氧化镓薄膜的剥离，势必促进其在相关器件中的应用。课题以纳米多孔GaN薄膜和多孔GaN分布布拉格反射镜（DBR）为衬底，利用其易于剥离的特点，采用MOCVD等方法制备大面积（>1英寸）、可转移的Beta-氧化镓单晶薄膜。系统研究生长和后退火条件对外延膜结构和性质的影响，确定高质量外延膜剥离的最佳制备工艺；研究Sn掺杂的氧化镓薄膜的掺杂性质与机理，并以肖特基势垒二极管为例，研究器件性能与生长条件间的相互关系；研究具有DBR结构、稀土元素掺杂的外延膜的掺杂性质与机理，制备发光器件，研究器件性能与生长条件间的相互关系。由于氧化镓薄膜可转移至多功能平台，因此该项目的开展将有助于氧化镓基器件与其它光电器件的集成，并为这类薄膜的应用提供重要的理论和实验数据。

具有宽带隙、高击穿电场的单晶Beta-氧化镓可制造耐高压功率器件、深紫外光电探测器和发光器件。由于同质外延衬底价格昂贵和导热导电能力差，因此若制备出高质量、导热和导电能力强、价格便宜的异质外延薄膜并实现剥离，势必促进其在相关器件中的应用。为了制备高质量Beta-Ga2O3单晶薄膜并实现转移，我们首先对纳米多孔（NP）GaN和NP-GaN分布布拉格反射镜（DBR）制备及剥离进行了研究。在此基础上，在多孔GaN薄膜（含DBR）、SrTiO3和KTaO3等衬底上异质外延Beta-Ga2O3单晶薄膜及掺杂薄膜，制备出具有晶格结构完整、载流子迁移率高和发光效率高的Beta-Ga2O3单晶薄膜，其主要研究内容如下：（1）首次采用退火技术制备多孔p型GaN外延膜，并异质外延出载流子迁移率高（40 cm2 V-1 s-1）、晶格结构完整的、高质量Ta掺杂Beta-Ga2O3单晶薄膜（MOCVD技术），有其所制备的自驱动深紫外光电探测器最大光电响应度可达8.67 A/W；（2）首次采用MOCVD和电化学刻蚀技术制备出晶格结构完整的、大面积可转移的Beta-Ga2O3单晶薄膜，有其所制备的日盲探测器最大光响应度为130mA/W@2V；(3)采用电化学刻蚀技术制备出高反射率（> 99%）的多孔GaN DBR和反射率高（>80%）、可转移的DBR镜，并异质外延生长出Eu掺杂Ga2O3单晶薄膜（PLD技术），其发光强度为参比薄膜的20倍。在此基础上，实现具有DBR镜的Beta-Ga2O3单晶薄膜的大面积转移，其发光强度呈现较明显的增强；（4）采用电化学刻蚀和PLD外延生长技术在纳米多孔GaN薄膜上外延晶格结构完整的Er掺杂Beta-Ga2O3单晶薄膜。与参比薄膜相比，生长在多孔GaN衬底上单晶薄膜的发光强度增加了2倍；（5）采用MOCVD技术在SrTiO3和KTaO3衬底外延出晶格结构完整、载流子浓度（1015-1018 cm-3）可调Beta-Ga2O3(100)单晶薄膜；（6）明确了上述单晶薄膜的外延生长机制、导电机理和发光机制。该项目的开展将有助于提升我国Ga2O3单晶薄膜的制备技术，并为这类薄膜的应用提供重要的理论和实验数据。