Understanding and controlling point defects in semiconductors are essential for developing advanced electronic and optoelectronic devices. Germanium telluride (GeTe), a semiconductor with a rhombohedral-to-cubic structural phase transition and a high concentration of intrinsic vacancies on the Ge sublattice, has recently attracted much interest for thermoelectric applications. However, the role of Ge vacancies in structural change and performance optimization remains obscure. Herein, we first unraveled the importance of Ge vacancies by combining first-principles calculations and Boltzmann transport theory. It is revealed that (1) Ge vacancies are more likely to spontaneously form in cubic GeTe, addressing its defective character; (2) Ge vacancies play a vital role in stabilizing cubic GeTe; and (3) Ge vacancies produce unfavorable band structure modification, leading to a reduced power factor. The following experiment found that AgInTe₂ alloying promotes a symmetry change from rhombohedral to cubic and deteriorates the thermoelectric performance, in good agreement with the abovementioned conclusions. More importantly, a single-phase cubic GeTe-based material with stable n-type conduction was first discovered based on the defect chemistry approach. Our findings shed new light on the critical role of Ge vacancies in the structure-property relationship and stimulate the strategy of point defect engineering for future thermoelectric applications.

了解和控制半导体中的点缺陷对于开发先进的电子和光电设备至关重要。碲化锗（GeTe）是一种具有菱形-立方结构相变且Ge子晶格上的本征空位高度集中的半导体，最近已引起热电应用的广泛兴趣。但是，Ge空位在结构变化和性能优化中的作用仍然不清楚。在这里，我们首先通过结合第一性原理计算和玻尔兹曼输运理论来阐明锗空位的重要性。结果表明：（1）Ge空位更容易自发形成立方GeTe，解决了其缺陷。（2）锗空位在稳定立方锗中起着至关重要的作用；（3）Ge空位产生不利的能带结构改变，导致功率因数降低。以下实验发现AgInTe₂合金化促进了从菱面体到立方体的对称性变化，并降低了热电性能，与上述结论非常吻合。更重要的是，首先基于缺陷化学方法发现了具有稳定n型导电性的单相立方GeTe基材料。我们的发现为锗空位在结构-性质关系中的关键作用提供了新的线索，并激发了用于未来热电应用的点缺陷工程策略。