| Transparent conducting oxides (TCOs), combining a high optical transparency and low conductive resistivity, have a wide range of applications in many fields such as photovoltaic, solar energy, flat panel displays, and field-effect transistor. Many oxide materials, such as ZnO, SnO2, and In2O3 are the most commonly systems, which have been applied as passive transparent conductive windows in active semiconducting devices, such as pn junctions, field effect transistors, and ultraviolet lasers. However, these materials still have some limitations such as instability of oxygen content, fatigue, and degradation. Thus, there has been a challenge to find an appropriate alternative transparent material to exhibit better properties. Perovskite-structured oxide is an important class of materials due to the good properties such as ferroeletricity, ferromagnetism, superconductivity, and piezoelectricity. At the same time, multilayer structure of perovskite materials for microelectronic materials and devices also have great potential applications. Therefore, there has been a great necessity for the further study on its structure and the physical mechanism.Alkaline earth stannates is a kind of perovskite materials, the general formula is RSnO3 (R=Ba, Sr, and Ca). They are important transparent materials due to good optical and electrical properties. It is a very important semiconductor material and it is widely used in many fields. Among RSnO3, BaSnO3 (BSO) is an ideally cubic perovskite-type oxide. It behaves as an n-type semiconductor, which has a wide bandgap and exhibits a high transmittance. And it remains stable up to 1000℃. The BSO material is used in the fields of physics, sensor device epitaxial structure and photoelectric techniques.Recent research shows that BSO doped with lanthanum (La) shows great advantages. La-doped BaSnO3 (BLSO) has a high mobility of 320 cm2V-1s-1. It has a bandgap of more than 4 eV, which is significantly larger than those from typical transparent conductive oxides. Consequently, BLSO is a promising candidate for transparent conductor applications and epitaxial multilayer devices. Recently, Shan et al. have explored an intrinsic relationship between optical properties and La concentration for BLSO system. There have also been some works on electronic band structure and infrared optical phonons of BLSO bulk material.Temperature dependence of optical properties and bandgap energy of BLSO film has not been studied to date. Therefore, it is desirable for us to conduct a more thorough study on the spectral behavior on the BLSO films. In this article, the BLSO films are grown on (0001) sapphire substrates by the sol-gel method. Temperature and concentration dependence of electronic transitions and optical properties has been systematically discussed.We reported that the temperature dependence of transmittance spectra of Ba1-xLaxSnO3 films with La concentration from x=0 to 0.10. The general regular of the transmission spectrum with temperature and composition has been obtained. The dielectric function and the bandgap energy of the BLSO film are obtained by fitting. We build a temperature-concentration double dependency model of BLSO films by fitting from Bose-Einstein model. The bandgap has a positive relationship with the concentration. However, it shows a negative relationship with the temperature. For lightly La doping (x≤0.04), the BLSO film has a strong dependence on the temperature and the concentration while it has a weak dependence for heavily La doping (x≥0.06).We also reported that the temperature dependence of electrical resistivity, and analysis of the concentration and temperature dependence of the resistivity of the materials. The characteristics of dependence is similar to its optical properties, which shows a strong dependence on lightly La doping and a weak dependence on heavily La doping. For heavily La doping, there has been a critical point of concentration. As the concentration exceeds the critical point, the bandgap energy increased significantly. For the internal mechanism, it is due to the variation of the lattice structure. The substitution for Ba ions form La ions causes the abnormal expansion of the BLSO films.In the semiconductor material electrical property testing system, the main work in this article is "temperature dependence Ⅰ-Ⅴ characteristic curve testing system" and "piezoelectricity testing system". During the research of the semiconductor materials, we usually need to test the various performances in a complex environment. In the past, the manual control of the instrument is complicated and inefficient, which requires a lot of time to set up the experimental instrument and record data. We are able to use a computer terminal to control multiple devices and realize integrated system function. The experimenter can achieve a comprehensive test function through the computer terminal, which has an important significance. |
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