INVESTIGATION ON ELECTRONIC CHARACTERISTICS OF SiGe MULTI-QUANTUM WELL CHANNEL MOSFETs ON A SOI SUBSTRATE

我们研制了一种基于超净技术的异质外延化学气相沉积装置，并利用该装置在硅或绝缘体上硅（SOI）衬底上生长了SiGe量子威尔斯阱。我们通过TEM、西姆斯和光致发光测试验证了威尔斯阱的物理性质，发现威尔斯阱没有缺陷，Si/SiGe界面非常尖锐。量子威尔斯阱的能级与理论能级一致。我们在SOI衬底上（这里使用SIMOX晶片）在550℃下生长了40 nm的Si，并用5.9 nm厚的栅氧化硅制作了PMOSFET。该器件的I-V特性与直接在SIMOX晶片上形成的PMOSFET的I-V特性几乎相同。结果表明，外延和器件工艺具有良好的精度和准确性。我们在SIMOX晶片上制作了SiGe量子阱沟道PMOSFET（栅极Si氧化物：5.9 nm，Si帽层：7 nm，SiGe合金的Ge分数：0.2，阱宽度：13 nm，SOI厚度：280 nm，SOI晶片上的Si缓冲层：40 nm）。我们通过饱和区和亚阈值区的I-V特性证实了SiGe阱中空穴的电流。对Si势垒高度为145 meV的单、三重SiGe量子威尔斯阱中重空穴的能级和电荷密度进行了数值计算。SiGe层中重空穴的有效质量取0.266 m0，层的介电常数取12.6。假设威尔斯井中的孔密度低于10 μ <10>cm 2<-3>。阐明了单量子威尔斯阱的能级与阱宽的关系，并论证了三量子威尔斯阱的能级或电荷密度与硅势垒宽度的关系。

We had developed a heteroepitaxial chemical vapor deposition apparatus on the basis of ultra-clean technology and grew SiGe quantum wells on a silicon or SOI (Silicon On Insulator) substrate by the apparatus. We verified the physical quality of the wells through TEM, SIMS and photoluminescence measurements and found that the wells were defect-free and the Si/SiGe interfaces were very sharp. The energy levels of the quantum wells agreed with those of the theoretical ones. We grew the 40-nm Si at 550℃ on a SOI substrate (a SIMOX wafer was here used) and fabricated a PMOSFET with the 5.9-nm-thick gate silicon oxide. The I-V characteristics of the device were almost all equal to those for the PMOSFET directly formed on a SIMOX wafer. The results indicated the good precision and accuracy of the epitaxial and device processes. We made SiGe-quantum-well-channel PMOSFETs on a SIMOX wafer (gate Si oxide : 5.9 nm, Si cap layer : 7 nm, Ge fraction of SiGe alloy : 0.2, well width : 13 nm, SOI thickness : 280 nm, Si buffer layer on a SOI wafer : 40 nm). We confirmed the current of holes confined to the SiGe well through the I-V characteristics in the saturation and subthreshold regions. Numerical calculation was carried out for the energy levels and charge densities of heavy holes in single and triple SiGe quantum wells with the Si barrier height of 145 meV.We used 0.266 m_0 as the effective mass of heavy holes in the SiGe layers and 12.6 as the permittivity of the layers. A low hole density below 10^<10> cm^<-3> in the wells was assumed. We clarified the energy levels of the single quantum wells related to the well width and demonstrated the relationship between the energy level or charge density and the Si Barrier width of the triple quantum wells.