In-memory computing could be used to improve energy efficiency but requires high-density memory cells. One way to increase memory density, while maintaining the same footprint, is to stack memory cells on top of each other. Although stacking is possible using conventional semiconductors (such as polycrystalline silicon), fabrication challenges (such as sidewall uniformity, doping profile variation, high thermal budgets and metal diffusion) can negatively impact performance. Peide Ye and colleagues now report a vertical thin-film transistor made using all-oxide semiconductors.

The researchers — who are based at Purdue University and Samsung Electronics — fabricated the devices via atomic layer deposition. They use an ultrathin indium oxide (In₂O₃) layer as the channel and a thick degenerate indium oxide layer as the gate electrode, which allows the metal diffusion that typically occurs in metal or nitride metal gate fabrication processes to be avoided. The process can also be used to make ferroelectric field-effect transistors, which exhibit a memory window of 1.85 V, an on/off ratio of 10⁴, a retention time of 10 years and an endurance of more than 10⁹ cycles.

内存计算可用于提高能源效率，但需要高密度存储单元。在保持相同占用空间的同时增加存储密度的一种方法是将存储单元堆叠在一起。尽管可以使用传统半导体（例如多晶硅）进行堆叠，但制造挑战（例如侧壁均匀性、掺杂分布变化、高热预算和金属扩散）可能会对性能产生负面影响。 Peide Ye 及其同事现在报告了一种使用全氧化物半导体制成的垂直薄膜晶体管。

来自普渡大学和三星电子的研究人员通过原子层沉积制造了这些设备。他们使用超薄氧化铟（In ₂ O ₃ ）层作为沟道，并使用厚的简并氧化铟层作为栅电极，这可以避免通常在金属或氮化物金属栅极制造工艺中发生的金属扩散。该工艺还可用于制造铁电场效应晶体管，其存储窗口为1.85 V，开/关比为10 ⁴ ，保留时间为10年，耐久性超过10 ^{9 个}周期。