Interface passivation and trap reduction via hydrogen fluoride for molybdenum disulfide on silicon oxide back-gate transistors

Layered semiconductor molybdenum disulfide (MoS2) has recently emerged as a promising material for flexible electronic and optoelectronic devices because of its finite bandgap and high degree of gate control. Here, we report a hydrogen fluoride (HF) passivation technique for improving the carrier mobility and interface quality of chemical vapor deposited monolayer MoS2 on a SiO2/Si substrate. After passivation, the fabricated MoS2 back-gate transistors demonstrate a more than double improvement in average electron mobility, a reduced gate hysteresis gap of 3 V, and a low interface trapped charge density of ~5.8 × 1011 cm−2. The improvements are attributed to the satisfied interface dangling bonds, thus a reduction of interface trap states and trapped charges. Surface x-ray photoelectron spectroscopy analysis and first-principles simulation were performed to verify the HF passivation effect. The results here highlight the necessity of a MoS2/dielectric passivation strategy and provides a viable route for enhancing the performance of MoS2 nano-electronic devices

Meta-analysis Followed by Replication Identifies Loci in or near CDKN1B, TET3, CD80, DRAM1, and ARID5B as Associated with Systemic Lupus Erythematosus in Asians

Systemic lupus erythematosus (SLE) is a prototype autoimmune disease with a strong genetic involvement and ethnic differences. Susceptibility genes identified so far only explain a small portion of the genetic heritability of SLE, suggesting that many more loci are yet to be uncovered for this disease. In this study, we performed a meta-analysis of genome-wide association studies on SLE in Chinese Han populations and followed up the findings by replication in four additional Asian cohorts with a total of 5,365 cases and 10,054 corresponding controls. We identified genetic variants in or near CDKN1B, TET3, CD80, DRAM1, and ARID5B as associated with the disease. These findings point to potential roles of cell-cycle regulation, autophagy, and DNA demethylation in SLE pathogenesis. For the region involving TET3 and that involving CDKN1B, multiple independent SNPs were identified, highlighting a phenomenon that might partially explain the missing heritability of complex diseases

Genome-Wide Association Study in Asian Populations Identifies Variants in ETS1 and WDFY4 Associated with Systemic Lupus Erythematosus

Systemic lupus erythematosus is a complex and potentially fatal autoimmune disease, characterized by autoantibody production and multi-organ damage. By a genome-wide association study (320 patients and 1,500 controls) and subsequent replication altogether involving a total of 3,300 Asian SLE patients from Hong Kong, Mainland China, and Thailand, as well as 4,200 ethnically and geographically matched controls, genetic variants in ETS1 and WDFY4 were found to be associated with SLE (ETS1: rs1128334, P = 2.33×10−11, OR = 1.29; WDFY4: rs7097397, P = 8.15×10−12, OR = 1.30). ETS1 encodes for a transcription factor known to be involved in a wide range of immune functions, including Th17 cell development and terminal differentiation of B lymphocytes. SNP rs1128334 is located in the 3′-UTR of ETS1, and allelic expression analysis from peripheral blood mononuclear cells showed significantly lower expression level from the risk allele. WDFY4 is a conserved protein with unknown function, but is predominantly expressed in primary and secondary immune tissues, and rs7097397 in WDFY4 changes an arginine residue to glutamine (R1816Q) in this protein. Our study also confirmed association of the HLA locus, STAT4, TNFSF4, BLK, BANK1, IRF5, and TNFAIP3 with SLE in Asians. These new genetic findings may help us to gain a better understanding of the disease and the functions of the genes involved

Metamorphic AlInAs/GaInAs HEMTs on GaAs substrates by MOCVD

Metamorphic AlInAs/GaInAs high-electron mobility transistors with very good device performance have been grown by metal-organic chemical vapor deposition (MOCVD), with the introduction of an effective multistage buffering scheme. Measured room-temperature Hall mobilities of the 2-DEG were over 8000 cm(2)/V . s with sheet carrier densities larger than 4 x 10(12) cm(-2). Transistors with 1-mu m gate length exhibited transconductance up to 626 mS/mm. The unity current gain cutoff frequency f(T) and the maximum oscillation frequency f(max) were 39.1 and 71 GHz, respectively. These results are very encouraging toward the manufacturing of metamorphic devices on GaAs substrates by MOCVD

Growth of ultra-high mobility In0.52Al0.48As/InxGa1−xAs (x ≥ 53%) quantum wells on Si substrates using InP/GaAs buffers by metalorganic chemical vapor deposition

InGaAs quantum wells (QWs) cladded by InAlAs barriers were grown on Si by metalorganic chemical vapor deposition. InP/GaAs/Si buffer templates were first prepared using a two-step growth method. We were able to significantly reduce the dislocation density in the upper InP buffer and obtain smooth surface morphology by fine-tuning the growth parameters and inserting an InGaAs interlayer in the InP buffer. On these InP/GaAs/Si compliant substrates, we investigated InGaAs QWs with various well/barrier parameters and Si-delta doping. We obtained two-dimensional electron gas mobilities over 10,000 cm2 V−1 s−1 at 300 K and above 39,000 cm2 V−1 s−1 at 77 K on Si substrates

Inverted-Type InGaAs Metal-Oxide-Semiconductor High-Electron-Mobility Transistor on Si Substrate with Maximum Drain Current Exceeding 2 A/mm

Inverted-type In0.51Al0.49As/In0.53Ga0.47As metal-oxide-semiconductor high-electron-mobility transistor grown by metal organic chemical vapor deposition on a Si substrate was demonstrated. 8 nm atomic-layer-deposited Al2O3 was used as gate dielectric. N++ InGaAs with an electron density of 4.5 x 10(19) cm(-3) was selectively regrown in the source/drain regions to reduce parasitic resistance while eliminating the conventional gate recess etching. 130-nm channel-length devices have exhibited a drain current up to 2.03 A/mm at V-ds = 0.6 V and an ultralow on-resistance of 163 Omega mu m. An effective mobility of 2975 cm(2) V-1 s(-1) was also extracted, indicating the high-quality epitaxial growth by metal organic chemical vapor deposition. (C) 2012 The Japan Society of Applied Physic

Fabrication of 100-nm Metamorphic AlInAs/GaInAs HEMTs Grown on Si Substrates by MOCVD

High-performance metamorphic Al0.49In0.51As-/Ga-0.47-In-0.53 As high-electron-mobility transistors (mHEMTs) grown on Si substrates by metal-organic chemical vapor deposition (MOCVD) using an effective multistage composite buffer scheme have been fabricated. Room-temperature Hall measurements show an average sheet carrier density of 4.5 x 10(12) cm(-2) with a mobility of over 7500 cm(2)/V . s. Maximum transconductance of mHEMTs with a 100-nm gate length was similar to 770 mS/mm, which is nearly the same as that of mHEMTs with the same dimension grown on GaAs substrates by MOCVD. The unity current gain cutoff frequency (f(T)) and the maximum oscillation frequency (f(max)) were 210 and 146 GHz, respectively. To our best knowledge, these results are the best reported for MOCVD-grown mHEMTs on Si

AlInAs/GaInAs mHEMTs on Silicon Substrates Grown by MOCVD

Metamorphic Al(0.50)In(0.50)As/Ga(0.47)In(0.53)As high electron mobility transistors (mHEMT) grown by Metalorganic Chemical Vapor Deposition (MOCVD) on silicon substrates have been successfully demonstrated for the first time. The grown structures exhibited 2-DEG mobilities over 4500 lcm(2)/V-s, with sheet carrier densities larger than 8 x 10(12) cm(-2) at room temperature. A 1.0-mu m transistor exhibits a maximum transconductance of 587mS/mm. The cut off and maximum oscillation frequencies were 32.3 and 44GHz, respectively.Metamorphic Al_0.50In_0.50As/Ga_0.47In _0.53As high electron mobility transistors (mHEMT) grown by Metalorganic Chemical Vapor Deposition (MOCVD) on silicon substrates have been successfully demonstrated for the first time. The grown structures exhibited 2-DEG mobilities over 4500 cm²/V-s, with sheet carrier densities larger than 8 x 10¹² cm^-2 at room temperature. A 10-μm transistor exhibits a maximum transconductance of 587mS/mm. The cut off and maximum oscillation frequencies were 32.3 and 44GHz, respectively