Hexagonal Si−Ge Class of Semiconducting Alloys Prepared by Using Pressure and Temperature

Abstract

Multi-anvil and laser-heated diamond anvil methods have been used to subject Ge and Si mixtures to pressures and temperatures of between 12 and 17 GPa and 1500-1800 K, respectively. Synchrotron angle dispersive X-ray diffraction, precession electron diffraction and chemical analysis using electron microscopy, reveal recovery at ambient pressure of hexagonal GeÀ Si solid solutions (P6 3 / mmc). Taken together, the multi-anvil and diamond anvil results reveal that hexagonal solid solutions can be prepared for all GeÀ Si compositions. This hexagonal class of solid solutions constitutes a significant expansion of the bulk GeÀ Si solid solution family, and is of interest for optoelectronic applications.

Structural transitions at high pressure and metastable phase in Si0.8Ge0.2

“…According to this study, the behaviour of the alloys follows that of the main component (Ge in case of Ge dominant alloy and Si in case of Si dominant alloy). The possibility to recover metastable phases was also observed by ex-situ HP-HT experiments for different SiGe compositions [29].…”

“…At lower pressure, the rhombohedral r8 phase partially transforms to another phase that can be indexed as the body-centered cubic structure (bc8). Pure bc8 was recovered for elemental Si and Ge [7], [9], [73], [74] and Si0.8Ge0.2 and binary [29], [75].…”

“…More recently, an hexagonal structure showing a tunable direct bandgap has received a huge interest because of potential applications in optoelectronics [26]. The hexagonal phase is obtained by heteroepitaxial growth of SixGe1-x on a nanowire of GaAs [26] and, interestingly, can be also synthesized by high-pressure and high-temperature (HP-HT) treatments [2], [27]- [29]. Surprisingly, while the amount of work dealing with phase transitions and transformations in pure silicon and germanium during the pressure cycle is significant, there are far fewer experimental studies on the high pressure (HP) behaviour of SixGe1-x alloys, and on the formation of their metastable phases after a pressure cycle.…”

Structural and Functional Properties of Si and Related Semiconducting Materials Processed by High-Pressure Torsion

“…98100) More recently, hexagonal Si 1¹x Ge x was obtained using multi-anvil and laser-heated diamond anvil methods. 61) However, the formation of metastable phases in SiGe alloys has not been studied so far. In order to investigate the metastable phases of SiGe alloys, we utilized homogeneous bulk Si 0.5 Ge 0.5 crystals obtained by the TLZ method, 6771) and performed HPT at the nominal pressure of 24 GPa using 5-mm diameter disks.…”

“…In addition, little work has been reported on the formation of metastable phases in SiGe alloys. 60,61) This overview paper focuses on recent HPT studies of Si and Si 0.5 Ge 0.5 alloy, and further discusses their phase transformations and electrical, thermal, and optical properties. 6264)…”