Fabrication and Charcterization of All Oxide-semiconductor PIN Diodes

氧化物材料由于具有多种本征功能，从电学到磁学、光学等领域都得到了广泛的应用。近年来半导体技术的发展将氧化物材料推向了电子学的最前沿，如果能找到氧化物材料的掺杂方法，它们将成为比现有半导体更强大的电子材料。这种梦想现在在我们目前的研究中正在实现。也就是说，氧化物材料的价态控制已经建立，就像普通半导体一样。现在，掺杂的氧化物可以被称为氧化物半导体。本课题组首次完成了全氧化物半导体PIN二极管的研制，遇到的第一个困难是存在于氧化物层中的陷阱（晶格缺陷引起的缺陷）。换句话说，这意味着通过PLD（脉冲激光沉积）方法生长的氧化物膜包含许多缺陷。现在，陷阱密度降低到<10 E17/cm 3，这可以有利地与高达> 10 E19的起始值相比。本文提出了一种利用PIN二极管结构测量陷阱密度的新方法，在PIN二极管的i层中插入铁电BaTiO_3和发射（激子）ZnO层，分别研究了少子注入和注入发光过程中的铁电性。最突出的结果是ZnO薄膜的形成，它提供了激子发光自由的深能级发射。这一成功是从一个新的发现，使得膜界面的精度控制可以通过ZnO/LaSrTiO 3的组合来实现。

By virtue of variety of intrinsic functions involing in, the oxide materials have been used in wide fields so far from the electronic to the magnetic and optical fields. Recent progress of the semiconducting technologies have pushed the oxide materials to the most front in the electronics.If some doping method for the oxide materials would be in our hand, they could serve as electronic materials more powerful than the existing semiconductors. This kind of dream is now coming true in our present research. Namely, the valence control of the oxide material has been established just like for the ordinary semiconductors. Now, the doped oxides can be called as the oxide semiconductors. First demonstration of the PIN diode prepared with all oxide semiconductors has been done by our group.The first obstacle we faced was the trap (defects arising from the lattice imperfection) existing in all oxide layeres. In other words, it means that the oxide films grown by the PLD (pulsed laser deposition) method contained a number of defects. Now, the trap density was reduced down to <10E17/cm3, which can be favorably compared with the starting value of as high as >10E19. In the work, we proposed a new measuring method of trap density using the PIN diode structure.We inserted the ferroelectric BaTiO3 and emissive (excitonic) ZnO layer as the i-layer of the PIN diode and explored the ferroelectricity during the minority carrier injection and injection luminescence, respectively. The outstanding result is the formation of ZnO film which provides the excitonic luminescence free from the deep level emission. This success was obtained from a new finding such that the film-interface precision control can be achieved by a combination of ZnO/LaSrTiO3.