Metal-induced n+/n homojunction for ultrahigh electron mobility transistors

A self-organized n+/n homojunction is proposed to achieve ultrahigh performance of thin film transistors (TFTs) based on an amorphous (Zn,Ba)SnO3 (ZBTO) semiconductor with sufficiently limited scattering centers. A deposited Al layer can induce a highly O-deficient (n+) interface layer in the back channel of a-ZBTO without damaging the front channel layer via the formation of a metal-oxide interlayer between the metal and back channel. The n+ layer can significantly improve the field-effect mobility by providing a relatively high concentration of free electrons in the front n-channel ZBTO, where the scattering of carriers is already controlled. In comparison with a Ti layer, the Al metal layer is superior, as confirmed by first-principles density functional theory (DFT) calculations, due to the stronger metal-O bonds, which make it easier to form a metal oxide AlOx interlayer through the removal of oxygen from ZBTO. The field-effect mobility of a-ZBTO with an Al capping layer can reach 153.4 cm2/Vs, which is higher than that of the pristine device, i.e., 20.8 cm2/Vs. This result paves the way for the realization of a cost-effective method for implementing indium-free ZBTO devices in various applications, such as flat panel displays and large-area electronic circuits. A layer of aluminum improves the performance of electronic devices useful for high-resolution flat displays, according to researchers in South Korea. Thin-film transistors are ultrafast electrical switches comprising stacked layers of semiconductors, metals and oxide materials. Their tiny size and planar architecture make them useful for large-area electronics and displays. A key performance metric for these devices is mobility: a measure of how quickly a charged particle can move through the semiconductor. Ji-Min Park from Chungnam National University in Daejeon and colleagues have shown how adding a capping layer of a highly oxidizing metal such as aluminum can greatly enhance the mobility of zinc barium tin oxide thin-film transistors. This cost-effective and useful improvement was achieved without introducing significant defects into the semiconductor. The formation of the conductive region (n+ layer) in (Zn,Ba)SnO3 (ZBTO) semiconductor is proposed to achieve high performance of thin-film transistors (TFTs). The aluminum metal capping layer is adopted to enhance the field-effect mobility of ZBTO TFTs. The capped Al layer takes out oxygen in the back-channel region, where the AlOx interlayer is formed. As a result, the field-effect mobility of Al-capped ZBTO TFTs is remarkably increased from 20.8 to 153.4 cm2/Vs. Furthermore, the Al-capped ZBTO TFTs are stable even when exposed to air for 3 months.