Formation of ultra-thin Ge_(1-x)Sn_x/Ge_(1-x-y)Si_xSn_y quantum heterostructures and their electrical properties for realizing resonant tunneling diode

摘要

Huge thermal noise owing to the narrow energy bandgap is one of the critical issues for group Ⅳ-based photonics in the mid-infrared regime. With this motivation, we examined to form Ge_(1-x)Sn_x/Ge_(1-x-y)Si_xSn_y quantum heterostructures (QHs) by molecular beam epitaxy for realizing resonant tunneling diodes composed of group-Ⅳ materials. We confirmed the formation of approximately 2nm-thick Ge_(1-x)Sn_x/Ge_(1-x)Si_xSn_y, QHs with atomically flat interfaces by x-ray diffraction and transmission electron microscopy methods. Moreover, by the current density-voltage (J-V) measurement at 10 K, we observed the occurrence of a non-linear distinct hump in the J-V characteristic, which is possibly originated from quantum transport of heavy holes. According to the tunneling transmission spectra simulation result, the hump property would be due to two possible scenarios: a resonant tunneling of heavy holes in the QH and/or a resonance phenomenon that heavy holes pass just above a potential barrier.