Abstract

In a metal/n-Ge structure, Fermi level pinning tends to occur. The insertion of an oxide layer at the interface between electrodes and n-Ge can effectively reduce the Schottky barrier height. However, the attachment of metal and oxide can cause diffusion of oxygen to the metal due to Gibbs free energy, which degrades the contact characteristics. In this study, we investigated the effects of a laminated electrode on the current density at a metal/GeO₂/n-Ge structure. Ni, Pt, Al, or Ti layers with thicknesses of 0.5–20 nm were formed, followed by a deposition of 200-nm-thick Al. The J–V curves of these samples showed that the current density of the Al/Ti/GeO₂/n-Ge structure was the largest among them and was about 126 times larger than that of the Al/GeO₂/n-Ge structure. We also found that the current density depended on the film thickness of Ti and was the highest at the film thickness of about 2.5 nm or less. To investigate the effect of the Ti interlayer on the current density, we obtained the depth profiles of X-ray photoelectron spectroscope spectra of the Al/Ti/GeO₂/n-Ge and Al/GeO₂/n-Ge structures. Analysis showed that the diffusion of the oxygen to Al was limited by the 20-nm-thick Ti, and the oxygen was diffused to Al when the film thickness of Ti was about 1 nm. These results demonstrate that laminated oxide structures such as AlO_x/TiO_x and TiO_x/GeO₂ can form on the sample with 1-nm-thick Ti, which increases the current density.

Graphic Abstract

抽象的

在金属/ n-Ge结构中，倾向于发生费米能级钉扎。在电极与n-Ge之间的界面处插入氧化物层可有效降低肖特基势垒高度。但是，由于吉布斯自由能，金属和氧化物的结合会导致氧向金属的扩散，从而降低了接触特性。在这项研究中，我们研究了层压电极对金属/ GeO ₂ / n-Ge结构上电流密度的影响。形成厚度为0.5–20 nm的Ni，Pt，Al或Ti层，然后沉积200 nm厚的Al。这些样品的J – V曲线表明，Al / Ti / GeO ₂的电流密度/ n-Ge结构是其中最大的，并且比Al / GeO ₂ / n-Ge结构的126倍大。我们还发现电流密度取决于Ti的膜厚，并且在约2.5 nm或更小的膜厚处最高。为了研究钛夹层对电流密度的影响，我们获得了Al / Ti / GeO ₂ / n-Ge和Al / GeO ₂ / n-Ge结构的X射线光电子能谱光谱的深度分布。分析表明，氧向Al的扩散受到厚度为20nm的Ti的限制，并且当Ti的膜厚度为约1nm时，氧扩散至Al。这些结果表明，诸如AlO _x / TiO _x和TiO的叠层氧化物结构_x / GeO ₂可以在Ti厚度为1 nm的样品上形成，这会增加电流密度。

图形摘要