Mn-doped SiGe thin films grown by UHV/CVD with room-temperature ferromagnetism and high hole mobility

具有室温铁磁性和高空穴迁移率的锰掺杂硅锗薄膜

In this work,silicon-germanium(SiGe)thin films are epitaxially grown on Ge substrates by ultra-high vacuum chemical vapor deposition and then doped with Mn element by ion-implantation and subsequent rapid thermal annealing(RTA).The characterizations show that the epitaxial SiGe thin films are single-crystalline with uniform tensile strain and then become polycrystalline after the ion implantation and following RTA.The magnetization measurements indicate that the annealed thin films exhibit Mn concentration-dependent ferromagnetism up to 309 K and the X-ray magnetic circular dichroism characterizations reveal the spin and orbital magnetic moments from the substitutional Mn element.To minimize the influence of anomalous Hall effect,magneto-transport measurements at a high magnetic field up to 31 T at 300 K are performed to obtain the hole mobility,which reaches a record-high value of~1230 cm^(2)V^(-1)s^(-1),owing to the crystalline quality and tensile strain-induced energy band modulation of the samples.The first demonstration of Mn-doped SiGe thin films with roomtemperature ferromagnetism and high carrier mobility may pave the way for practical semiconductor spintronic applications.

本文采用超高真空化学气相沉积系统在锗衬底上外延生长了第IV族硅锗薄膜,然后通过离子注入和快速热退火进行锰元素掺杂.结构测试表明,外延的硅锗薄膜是具有均匀拉伸应变的单晶,随后的离子注入和快速热退火使其变为多晶.磁性测试表明,退火后的薄膜表现出依赖于锰掺杂浓度的铁磁性,居里温度最高可达309 K;X射线磁圆二色谱揭示了替代位锰元素的自旋和轨道磁矩.为最大限度地减少反常霍尔效应的影响,磁输运测试在高达31 T的强磁场下进行,该薄膜在300 K温度下空穴迁移率达到创纪录的~1230 cm^(2)V_(−1)s^(−1).此高迁移率归因于样品较高的结晶质量和拉伸应变对能带的调制.本文首次展示了具有室温铁磁性和高载流子迁移率的锰掺杂硅锗薄膜,有望促进基于第IV族半导体的自旋电子材料与器件的实际应用.