Combined Iodine- and Sulfur-Based Treatments for an Effective Passivation of GeSn Surface

Abstract

GeSn alloys are metastable semiconductors that have been proposed as building blocks for silicon-integrated short-wave and mid-wave infrared photonic and sensing platforms.Exploiting these semiconductors requires, however, the control of their epitaxy and their surface chemistry to reduce non-radiative recombination that hinders the efficiency of optoelectronic devices. Herein, we demonstrate that a combined sulfur-and iodine-based treatments yields effective passivation of Ge and Ge0.9Sn0.1 surfaces. X-ray photoemission spectroscopy and in situ spectroscopic ellipsometry measurements were used to investigate the dynamics of surface stability and track the reoxidation mechanisms. Our analysis shows that the largest reduction in oxide after HI treatment, while HF+(NH4)2S results in a lower reoxidation rate. A combined HI+(NH4)2S treatment preserves the lowest oxide ratio <10 % up to 1 hour of air exposure, while less than half of the initial oxide coverage is reached after 4 hours. These results highlight the potential of S-and I-based treatments in stabilizing the GeSn surface chemistry thus enabling a passivation method that is compatible with materials and device processing.

Scalable fabrication of self-assembled GeSn vertical nanowires for nanophotonic applications

“…Hence, the GeSn NW PD presents a high reverse dark current at room temperature while an ultrasmall reverse dark current at 77 K due to suppression of Shockley–Read–Hall (SRH) recombination via surface traps at low temperature. Through surface defect removing (such as digital etching [ 44 ]) and surface passivation [ 45 ] techniques, the reverse dark current can be further suppressed.…”

Room Temperature Lasing in GeSn Microdisks Enabled by Strain Engineering

“…[13] Further strategies, combining quantum confinement of carriers and strain engineering of the band structure, should have a high potential to overcome point defects and surface recombination losses, and to reach the room temperature lasing with significantly reduced thresholds. [18,31,32]…”

Surface bonding state of germanium via cyclic dry treatments using plasma of hydrogen iodine and pure oxygen gases

“…In the wet process case, hydroiodic acid (HI) solution removes Ge oxide, and the iodine atoms terminate Ge surface. 33,34) Iodine terminated Ge surface is relatively stable even under long air exposure compared with other hydrogen halide counterparts, such as HF, HCl, and HBr. 33) The larger halogen atoms serve as a better steric barrier to prevent re-oxidation of the Ge surface.…”