Marinus Hopstaken

High Efficiency Cu2ZnSn(S,Se)4 Solar Cells by Applying a Double In2S3/CdS Emitter

High-efficiency Cu2ZnSn(S,Se)4 solar cells are reported by applying In2S3/CdS double emitters. This new structure offers a high doping concentration within the Cu2ZnSn(S,Se)4 solar cells, resulting in a substantial enhancement in open-circuit voltage. The 12.4% device is obtained with a record open-circuit voltage deficit of 593 mV.

Band alignment at the Cu2ZnSn(SxSe1−x)4/CdS interface

Energy band alignments between CdS and Cu2ZnSn(SxSe1−x)4 (CZTSSe) grown via solution-based and vacuum-based deposition routes were studied as a function of the [S]/[S+Se] ratio with femtosecond laser ultraviolet photoelectron spectroscopy, photoluminescence, medium energy ion scattering, and secondary ion mass spectrometry. Band bending in the underlying CZTSSe layer was measured via pump/probe photovoltage shifts of the photoelectron spectra and offsets were determined with photoemission under flat band conditions. Increasing the S content of the CZTSSe films produces a valence edge shift to higher binding energy and increases the CZTSSe band gap. In all cases, the CdS conduction band offsets were spikes.

Sharp Reduction of Contact Resistivities by Effective Schottky Barrier Lowering With Silicides as Diffusion Sources

An extremely low contact resistivity of 6-7 × 10^-9 Ω·cm² between Ni_0.9Pt_0.1Si and heavily doped Si is achieved through Schottky barrier engineering by dopant segregation. In this scheme, the implantation of B or As is performed into silicide followed by a low-temperature drive-in anneal. Reduction of effective Schottky barrier height is manifested in the elimination of nonlinearities in IV characteristics.

Understanding mobility mechanisms in extremely scaled HfO 2 (EOT 0.42 nm) using remote interfacial layer scavenging technique and V t -tuning dipoles with gate-first process

We demonstrate a novel “remote interfacial layer (IL) scavenging” technique yielding a record-setting equivalent oxide thickness (EOT) of 0.42 nm using a HfO2-based MOSFET high-к gate dielectric. Intrinsic effects of IL scaling on carrier mobility are clarified using this method. We reveal that the mobility degradation observed for La-containing high-к is not due to the La dipole but due to the intrinsic IL scaling effect, whereas an Al dipole brings about additional mobility degradation. This unique nature of the La dipole enables aggressive EOT scaling in conjunction with IL scaling for the 16 nm technology node without extrinsic mobility degradation.

Oxygen passivation of vacancy defects in metal-nitride gated HfO2/SiO2/Si devices

We show that oxygen can be diffused through thin TiN layers to correct flatband voltage offsets in HfO2/SiO2/Si structures, achieving nearly band-edge capacitance voltage characteristics without undue growth of parasitic SiO2. Photoemission reveals that the TiN remains conductive despite mild oxidation, although over-oxidation results in insulating layers. Secondary ionization mass spectroscopy of samples treated with isotopically labeled O18 was used to assess how much oxygen is required to fully passivate the defects caused by thermal processing of metallized HfO2/SiO2/Si devices.

Ultra Low Contact Resistivities for CMOS Beyond 10-nm Node

Contact resistances are directly measured for contacts with sizes from 25 to 330 nm using e-beam based nano-TLM devices. Record low contact resistivities ~1.5 × 10^-9 Ω· cm² are extracted from Ni(Pt) silicide contacts on in situ boron-doped Si_0.7Ge_0.3 with a chemical boron-doping density of 2 × 10²¹/cm³. This is very promising for pMOS applications beyond the 10-nm node. A clear dependence of contact resistance on the silicide thickness has also been found.

Characterization of thin epitaxial emitters for high-efficiency silicon heterojunction solar cells

We report silicon heterojunction solar cells with conversion efficiencies exceeding 21% using appropriately designed emitter structures comprised of highly doped thin epitaxial layers grown by plasma-enhanced chemical vapor deposition at temperatures close to 200 °C. We show that at a given doping concentration, there is an optimum epitaxial layer thickness, above which the conversion efficiency is limited by Auger recombination and bandgap narrowing within the epitaxial layer. In contrast, below the optimum thickness, the conversion efficiency is limited by carrier recombination at the emitter surface of the crystalline silicon substrate.

Self-aligned III-V MOSFETs: Towards a CMOS compatible and manufacturable technology solution

We demonstrate self-aligned fully-depleted III-V MOSFETs using CMOS-compatible device structures and manufacturable process flows. Processes with good manufacturability and scalability, such as, gate definition and spacer formation using RIE, and formation of self-aligned source/drain extensions (SDE) and self-aligned raised source/drain (RSD), have been established on III-Vs. We demonstrate short-channel devices down to gate length LG = 30 nm. Our best short-channel devices exhibit peak saturation transconductance GMSAT = 1140 μS/μm at LG = 60 nm and supply voltage VDD = 0.5 V.

Confinement and integration of magnetic impurities in silicon

Integration of magnetic impurities into semiconductor materials is an essential ingredient for the development of spintronic devices such as dilute magnetic semiconductors. While successful growth of ferromagnetic semiconductors was reported for III-V and II-VI compounds, efforts to build devices with silicon technology were hampered by segregation and clustering of magnetic impurities such as manganese (Mn). Here, we report on a surface-based integration of Mn atoms into a silicon host. Control of Mn diffusion and low-temperature silicon epitaxy lead to confined Mn δ-layers with low interface trap densities, potentially opening the door for a new class of spintronic devices in silicon.

Density change upon crystallization of Ga-Sb films

Besides crystallization time and temperature, the mass density change upon crystallization is a key parameter governing the reliability of phase change random access memory. Indeed, few percentages density change induces considerable mechanical stress in memory cells, leading to film delamination with subsequent electrical failures. This letter presents an extensive study of density change upon crystallization in a series of Ga-Sb thin films with various antimony contents. The mass density of the films is precisely determined by x-ray reflectivity in both their amorphous and crystalline states. The variations of the density in crystalline and amorphous films according to the Sb content found to cross with a zero-density change for 70 at. % Sb. The peculiar behavior of Ga-Sb thin films upon crystallization may be linked to their stress state and mechanical properties.