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Structural and electrical characteristics of epitaxial germanium (Ge) heterogeneously integrated on silicon (Si) via a composite, large bandgap AlAs/GaAs buffer are investigated. Electrical characteristics of N-type metal-oxide-semiconductor (MOS) capacitors, fabricated from the aforementioned material stack are then presented. Simulated and experimental X-ray rocking curves show distinct Ge, AlAs, and GaAs epilayer peaks. Moreover, secondary ion mass spectrometry, energy dispersive X-ray spectroscopy (EDS) profile, and EDS line profile suggest limited interdiffusion of the underlying buffer into the Ge layer, which is further indicative of the successful growth of device-quality epitaxial Ge layer. The Ge MOS capacitor devices demonstrated low frequency dispersion of 1.80% per decade, low frequency-dependent flat-band voltage, V FB , shift of 153 mV, efficient Fermi level movement, and limited C-V stretch out. Low interface state density (D it ) from 8.55 × 10 11 to 1.09 × 10 12 cm −2 eV −1 is indicative of a high-quality oxide/Ge heterointerface, an effective electrical passivation of the Ge surface, and a Ge epitaxy with minimal defects. These superior electrical and material characteristics suggest the feasibility of utilizing large bandgap III-V buffers in the heterointegration of high-mobility channel materials on Si for future high-speed complementary metal-oxide semiconductor logic applications.INDEX TERMS Germanium (Ge), heteroepitaxy, metal-oxide semiconductor (MOS) devices, silicon (Si), III-V materials.

The growth, morphological, and electrical properties of thin-film Ge grown by molecular beam epitaxy on Si using a two-step growth process were investigated. High-resolution x-ray diffraction analysis demonstrated ∼0.10% tensile-strained Ge epilayer, owing to the thermal expansion coefficient mismatch between Ge and Si, and negligible epilayer lattice tilt. Micro-Raman spectroscopic analysis corroborated the strain-state of the Ge thin-film. Cross-sectional transmission electron microscopy revealed the formation of 90  ° Lomer dislocation network at Ge/Si heterointerface, suggesting the rapid and complete relaxation of Ge epilayer during growth. Atomic force micrographs exhibited smooth surface morphology with surface roughness < 2 nm. Temperature dependent Hall mobility measurements and the modelling thereof indicated that ionized impurity scattering limited carrier mobility in Ge layer. Capacitance- and conductance-voltage measurements were performed to determine the effect of epilayer dislocation density on interfacial defect states (Dit) and their energy distribution. Finally, extracted Dit values were benchmarked against published Dit data for Ge MOS devices, as a function of threading dislocation density within the Ge layer. The results obtained were comparable with Ge MOS devices integrated on Si via alternative buffer schemes. This comprehensive study of directly-grown epitaxial Ge-on-Si provides a pathway for the development of Ge-based electronic devices on Si.

BACKGROUND:Civilian extremity trauma with vascular injury carries a significant risk of morbidity, limb loss, and mortality. We aim to describe the trends in extremity vascular injury repair and compare outcomes between trauma and vascular surgeons. METHODS:We performed a single-center retrospective review of patients 18 years or older with extremity vascular injury requiring surgical intervention between January 2009 and December 2019. Demographics, injury characteristics, operative course, and hospital course were analyzed. Descriptive statistics were used to examine management trends, and outcomes were compared for arterial repairs. Multivariate regression was used to evaluate surgeon specialty as a predictor of complications, readmission, vascular outcomes, and mortality. RESULTS:A total of 231 patients met our inclusion criteria; 80% were male with a median age of 29 years. The femoral vessels were most commonly injured (39.4%), followed by the popliteal vessels (26.8%). Trauma surgeons performed the majority of femoral artery repairs (82%), while vascular surgeons repaired the majority of popliteal artery injuries (84%). Both had a similar share of brachial artery repairs (36% vs. 39%, respectively). There were no differences in complications, readmission, vascular outcomes, and mortality. Median time from arrival to operating room was significantly shorter for trauma surgeons. There was a significant downward trend between 2009 and 2017 in the proportion of total and femoral vascular procedures performed by trauma surgeons. On multivariate regression, surgical specialty was not a significant predictor of need for vascular reintervention, prophylactic or delayed fasciotomies, postoperative complications, or readmissions. CONCLUSION:Traumas surgeons arrived quicker to the operating and had no difference in short-term clinical outcomes of brachial and femoral artery repairs compared with patients treated by vascular surgeons. Over the last decade, there has been a significant decline in the number of open vascular repairs done by trauma surgeons.