The impact of strain engineering on hole mobility of In(x)Ga(1-x)As channels for III-V pMOSFET

Whilst the high electron mobility of compound semiconductors makes them attractive for beyond 22 nm CMOS, a key challenge in implementing III-V materials is their modest hole mobility. Addressing this issue motivates an investigation of the impact of strain to optimize the hole transport properties of III-V MOSFET channel materials. In this work, the researchers describe the dependence of hole mobility on the bi-axial compressive strain of InxGa1-xAs layers with indium concentrations in the range 53%-85%. The vertical architecture of the material structure of this study resembles a III-V high mobility transistor where the dopant is spatially separated from the device channel. Mobility and channel carrier concentration were determined using Hall effect measurements. While the 53% In-content (0% strain) structures demonstrated modest mobilities of 60-70 cm2/Vs, the strained structures exhibited superior transport with the 85% In-content (2.1% strain) channel demonstrating mobilities of 427-433 cm2/Vs with sheet hole densities of 1.33e12 - 1.6e12 cm-2 depending on the doping level used. To their knowledge, the room temperature mobility of the 2.1% strained structures are the highest ever reported for an InxGa1-xAs channel

Critical current diffraction pattern of SIFS Josephson junctions with step-like F-layer

We present the latest generation of superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions with a step-like thickness of the ferromagnetic (F) layer. The F-layer thicknesses $d_1$ and $d_2$ in both halves were varied to obtain different combinations of positive and negative critical current densities $j_{c,1}$ and $j_{c,2}$. The measured dependences of the critical current on applied magnetic field can be well described by a model which takes into account different critical current densities (obtained from reference junctions) and different net magnetization of the multidomain ferromagnetic layer in both halves.Comment: 7 pages, 3 figure

Fabrication and characterization of short Josephson junctions with stepped ferromagnetic barrier

We present novel low-T_c superconductor-insulator-ferromagnet-superconductor (SIFS) Josephson junctions with planar and stepped ferromagnetic interlayer. We optimized the fabrication process to set a step in the ferromagnetic layer thickness. Depending on the thickness of the ferromagnetic layer the ground state of the SIFS junction has a phase drop of either 0 or pi. So-called 0-pi Josephson junctions, in which 0 and pi ground states compete with each other, were obtained. These stepped junctions may have a double degenerate ground state, corresponding to a vortex of supercurrent circulating clock- or counterclockwise and creating a magnetic flux which carries a fraction of the magnetic flux quantum \Phi_0. Here, we limit the presentation to static properties of short junctions

An investigation of (NH4)2S passivation on the electrical, and interfacial properties of the Al2O3/GaSb system for p-type and n-type GaSb layers

III-V materials have emerged as potential candidates to replace silicon in metal-oxide-semiconductor (MOS) devices for logic applications beyond the 15nm technology node. GaSb, in particular, offers a means to realizing a high-performance, low-power complementary logic solution owing to its high electron and hole mobilities. However, achieving a passivated, high-quality III-V/dielectric interface remains the biggest impediment to implementing a III-V logic solution. Among the various surface passivation strategies developed to engineer an improved interface, sulfur passivation ((NH4)2S) has been successful on GaAs and InGaAs. However, there is little discussion in the literature regarding this strategy on GaSb. In this work, we address the effectiveness of sulfur passivation, under differing (NH4)2S concentrations, on n-type and p-type GaSb MOS capacitors. The samples were chemically treated in 1%, 5%, 10% or 22% (NH4)2S solutions for 10 min at 295 K, prior to atomic-layer-deposition (ALD) of Al2O3. The capacitors were electrically and physically characterised using capacitance-voltage (C-V) measurements and transmission electron microscopy (TEM). Capacitors treated with 1% solution exhibited the largest capacitance modulation by the gate. The capacitance modulation and maximum accumulation capacitance decreased with increased (NH4)2S concentrations due to enhanced chemical etching of the GaSb surface resulting in degraded interface. Atomic force microscopy (AFM) further revealed the etching characteristics of GaSb in (NH4)2S as well as the etched surface roughness which are important when realizing GaSb transistors