Si/SiGe Multiple-Quantum-well Resonant Tunneling Device

共振隧穿器件。已经被归类为速度最快的器件之一，超过了2D器件，如HEMT和MODFET，以及JJ器件，并有望满足从GHz到THz的高速操作需求。到目前为止，隧道器件已被应用于获得高隧道势垒的III-V材料系统。如果实现了Si/SiGe隧道效应器件，我们可以扩展一种新的硅基超高速集成器件系统。然而，自1988年首次报道a Si/SiGe RTD以来，I-V曲线负阻(NDR)区的峰谷电流比(PVCR)一直很低，在RT时为1.2。在理论分析的基础上，我们首次将电子隧穿和多量子阱相结合应用于a-Si/SiGe RTD，并在1998年成功地提高了a-Si/SiGe RTD的PVCR值，获得了大于7.6的PVCR值。在这项工作中，我们进一步研究了RTD器件的结构和工艺，以增强NDR效应。结果，我们发现应变释放缓冲器的表面结晶质量对NDR性能有很大的影响，并提出了一种退火薄的双层缓冲器和一种退火薄的多层缓冲器，该缓冲器具有薄的SiGe层和高浓度的Ge。所提出的缓冲液具有高结晶质量的表面。通过在电子隧道多势垒RTD中引入高晶体质量的缓冲器，我们成功地实现了在RT时PVCR值大于180，这与III-V RTD相当或更高。这一结果表明了SiGe RTDS中非常低的非弹性散射的重要器件物理特性。研究表明，采用SiGe材料可以获得与III-V RTD相当的PVCR性能，这为进一步推广Si/SiGe隧道器件提供了巨大的动力。

Resonant tunneling devices. Have been categorized into one of the highest speed devices which surpass 2D devices, such as HEMT and MODFET, and JJ devices, and have been expected to meet the demand for high speed operations from GHz to THz. So far, the tunneling devices have been applied to III-V material systems with which high tunneling barriers are obtained. If Si/SiGe tunneling devices are realized, we can expand a new Si-based ultra-high speed integration device system. However, the peak-to-valley current ratio (PVCR), in the negative differential resistance (NDR) region of, the I-V curve, as a figure of merit, has been low and 1.2 at RT since the first report of a Si/SiGe RTD in 1988. On the basis of the theoretical analysis, we have applied for the first time a combination of electron tunneling and a multiple quantum well to a Si/SiGe RTD and have succeeded in enhancing the PVCR value of a Si/SiGe RTD and obtaining a PVCR value of more than 7.6 in 1998. In this work, we have further investigated the RTD device structure and process to enhance the NDR effect. As a result, we have found that the surface crystalline quality of a strain-relief buffer largely affects the NDR performance, and have proposed an annealed thin two-layer buffer and an annealed thin multi-layer buffer, which has a thin SiGe layer with a high concentration of Ge. The proposed buffers exhibit surfaces with high crystallin quality. By introducing the high crystalline quality buffer to a electrontunneling multiple-well RTD, we have succeeded in realizing a PVCR value of more than 180 at RT which is comparable to or more than those of III-V RTDs. This result indicates the important device physics of very low inelastic scattering in SiGe RTDs. Through this research, it has' been demonstrated that the PVCR performance comparable to those of III-V RTDs has been obtained by the use of SiGe materials, which gives a great motive force to further extend Si/SiGe tunneling devices.