Errol Antonio C. Sanchez

Demonstration of a Ge/GeSn/Ge Quantum-Well Microdisk Resonator on Silicon: Enabling High-Quality Ge(Sn) Materials for Micro- and Nanophotonics

We theoretically study and experimentally demonstrate a pseudomorphic Ge/Ge0.92Sn0.08/Ge quantum-well microdisk resonator on Ge/Si (001) as a route toward a compact GeSn-based laser on silicon. The structure theoretically exhibits many electronic and optical advantages in laser design, and microdisk resonators using these structures can be precisely fabricated away from highly defective regions in the Ge buffer using a novel etch-stop process. Photoluminescence measurements on 2.7 μm diameter microdisks reveal sharp whispering-gallery-mode resonances (Q > 340) with strong luminescence.

Hole Mobility Enhancement in Compressively Strained

Germanium tin (GeSn) pMOSFETs with channel Sn composition of 7% are fabricated using a low thermal budget process. GeSn pMOSFETs show enhancement in hole mobility over control Ge devices by 85% in high inversion charge density regime. Hole mobility improvement observed in GeSn channel pMOSFETs compared with Ge control is due to the biaxial compressive strain in GeSn resulting from epitaxial growth of GeSn thin films on relaxed Ge buffer layers.

{\rm Ge}_{0.93}{\rm Sn}_{0.07}

We have studied silicon nitride thin films deposited by hot-wire chemical vapor deposition as a function of the substrate temperature and hydrogen dilution. We found that adding H2 to the process significantly enhances silicon nitride film deposition. High-quality films can be grown at low substrate temperatures (<350 °C). At optimized conditions, a 500-A-thick silicon nitride film gives a nearly 100% surface coverage on a 100 nm scale object. H dilution dramatically increases the NH2 radicals in the process and leads to conformal films.

pMOSFETs

We present a new etch chemistry that enables highly selective dry etching of germanium over its alloy with tin (Ge(1-x)Sn(x)). We address the challenges in synthesis of high-quality, defect-free Ge(1-x)Sn(x) thin films by using Ge virtual substrates as a template for Ge(1-x)Sn(x) epitaxy. The etch process is applied to selectively remove the stress-inducing Ge virtual substrate and achieve strain-free, direct band gap Ge0.92Sn0.08. The semiconductor processing technology presented in this work provides a robust method for fabrication of innovative Ge(1-x)Sn(x) nanostructures whose realization can prove to be challenging, if not impossible, otherwise.

Conformal thin-film silicon nitride deposited by hot-wire chemical vapor deposition

Metal organic chemical vapor deposition of GaAs, InGaAs, and AlGaAs on nominal 300 mm Si(100) at temperatures below 550 °C was studied using the selective aspect ratio trapping method. We clearly show that growing directly GaAs on a flat Si surface in a SiO2 cavity with an aspect ratio as low as 1.3 is efficient to completely annihilate the anti-phase boundary domains. InGaAs quantum wells were grown on a GaAs buffer and exhibit room temperature micro-photoluminescence. Cathodoluminescence reveals the presence of dark spots which could be associated with the presence of emerging dislocation in a direction parallel to the cavity. The InGaAs layers obtained with no antiphase boundaries are perfect candidates for being integrated as channels in n-type metal oxide semiconductor field effect transistor (MOSFET), while the low temperatures used allow the co-integration of p-type MOSFET.

Highly Selective Dry Etching of Germanium over Germanium–Tin (Ge1–xSnx): A Novel Route for Ge1–xSnx Nanostructure Fabrication

High quality GaAs is selectively grown in 40 nm width Shallow Trench Isolation patterned structures. The patterned wafers have a V-shape Si (111) surface obtained by Tetramethylammonium hydroxide etching. By employing a SiCoNi™ pre-epi clean and two-step growth procedure (low temperature buffer and high temperature main layer), defects are effectively confined at the trench bottom, leaving a dislocation-free GaAs layer at the upper part. The high crystal quality is confirmed by transmission electron microscopy. Scanning spreading resistance microscopy indicates a high resistance of GaAs. The process conditions and GaAs material quality are highly compatible with Si technology platform.

Low defect InGaAs quantum well selectively grown by metal organic chemical vapor deposition on Si(100) 300 mm wafers for next generation non planar devices

High-quality amorphous silicon nitrides were deposited by hot-wire chemical vapor deposition using SiH4, NH3, and H2 gases. These films show a high deposition rate of 5A∕s, a low processing temperature of 300°C, an excellent conformal coverage, a low etching rate of 7A∕min, an index of refraction of 2.1, an optical band gap of 4.0eV, and a high breakdown field of 3MV∕cm. The effects of hydrogen dilution, substrate temperature, chamber pressure, and filament temperature on silicon nitride film property were studied to optimize the process. We found that adding H2 to the processing significantly enhances the silicon nitride films’ properties. The N content in the film increased significantly based on the infrared measurement. Hydrogen dilution is believed to play a key role for the conformal silicon nitride film. Hydrogen dilution also improves the process in that the gas ratio of NH3∕SiH4 has been greatly reduced with the assistance of the H2 gas. With substrate temperatures varying from 23°to400°C, this s...

Selective metal-organic chemical vapor deposition growth of high quality GaAs on Si(001)

The effect of phosphorus implantation and thermal annealing on properties of Si:C epitaxial films was investigated. High resolution x-ray diffraction analysis and secondary ion mass spectroscopy indicated that spike annealing only causes slight loss of substitutional carbon. Phosphorus implantation, even with low energy, could cause surface damages and loss of substitutional carbon. Although spike annealing effectively activates implanted phosphorus, it also results in significant substitutional carbon loss (from 1.2% to less than 0.5%) within the phosphorus diffused layer. The interaction of carbon and phosphorus resulted in a junction profile as abrupt as with 3 nm/decade.

Amorphous silicon nitride deposited by hot-wire chemical vapor deposition

We have obtained Anti-Phase Boundary (APB) free GaAs epilayers on “quasi-nominal” (001) silicon substrates, while using a thick germanium strain relaxed buffer between the GaAs layer and the silicon substrate in order to accommodate the 4% lattice mismatch between the two. As silicon (001) substrates always have a small random offcut angle from their nominal surface plane, we call them “quasi-nominal.” We have focused on the influence that this small (≤0.5°) offcut angle has on the GaAs epilayer properties, showing that it greatly influences the density of APBs. On 0.5° offcut substrates, we obtained smooth, slightly tensile strained (R = 106%) GaAs epilayers that were single domain (e.g., without any APB), showing that it is not necessary to use large offcut substrates, typically 4° to 6°, for GaAs epitaxy on silicon. These make the GaAs layers more compatible with the existing silicon manufacturing technology that uses “quasi-nominal” substrates.

A study of low energy phosphorus implantation and annealing in Si:C epitaxial films

The growth of epitaxy of silicon–carbon (Si1−yCy) alloy layers on (1 0 0) silicon substrates by chemical vapour deposition (CVD) with a novel precursor, neopentasilane, as the silicon source gas and methylsilane as the carbon source is reported. High quality Si1−yCy alloy layers at growth rates of 18 nm min −1 and 13 nm min −1 for fully substitutional carbon levels of 1.8% and 2.1%, respectively, were achieved. The highest substitutional carbon level achieved was 2.6% (strained perpendicular lattice constant of 5.347 u A) as determined by x-ray diffraction. (Some figures in this article are in colour only in the electronic version)