A pseudo-single-crystalline germanium film for flexible electronics

Abstract

We demonstrate large-area (∼600 μm), (111)-oriented, and high-crystallinity, i.e., pseudo-single-crystalline, germanium (Ge) films at 275 °C, where the temperature is lower than the softening temperature of a flexible substrate. A modulated gold-induced layer exchange crystallization method with an atomic-layer deposited Al2O3 barrier and amorphous-Ge/Au multilayers is established. From the Raman measurements, we can judge that the crystallinity of the obtained Ge films is higher than those grown by aluminum-induced-crystallization methods. Even on a flexible substrate, the pseudo-single-crystalline Ge films for the circuit with thin-film transistor arrays can be achieved, leading to high-performance flexible electronics based on an inorganic-semiconductor channel.

Orientation control of intermediate-composition SiGe on insulator by low-temperature Al-induced crystallization

“…Several attempts have been made to fabricate high-quality SiGe alloys through layer exchange [34][35][36][37][38][39][40][41]. Large-grained (~10 µm), preferentially (111)-oriented SGOIs were achieved when the Si or Ge compositions were low (< 20%); however, the grain size and (111)-orientation fraction deteriorated as SiGe approached the intermediate compositions (20-80%) [37,39].…”

Direct synthesis of multilayer graphene on an insulator by Ni-induced layer exchange growth of amorphous carbon

“…In the field of group-IV semiconductors including Si, [27][28][29][30][31] Ge, [32][33][34][35] and SiGe, 36,37 metal-induced layer exchange (MILE) allows large-grained (>30 lm) highly oriented thin films to be formed on insulators. In MILE, an amorphous semiconductor layer crystallizes by "layer exchange" between the amorphous layer and a catalyst metal layer.…”

Effects of gold‐induced crystallization process on the structural and electrical properties of germanium thin films

“…After 10 days of annealing at 300°C, Al regions were interconnected with each other; in other words, layer exchange occurred. Furthermore, there are many studies where the annealing time is too long for Au‐induced layer exchange crystallization . In this study, Au‐rich regions were not interconnected with each other so no layer exchange was observed.…”

“…Therefore, MIC method is the most promising method to obtain high quality poly‐Ge films at temperatures much lower than those required in the absence of a metal catalyst. In MIC, Al, Au, and Ag have been used as the catalyst metals for crystallizing α ‐Ge films. These metals can lower the crystallization temperature of α ‐Ge films by forming eutectic alloy during thermal annealing .…”