Showing papers by "Samit K. Ray published in 1997"

Electrical properties of oxides grown on strained Si using microwave N2O plasma

Abstract: Microwave plasma oxidation (below 200 °C) of strained Si on relaxed Si1−xGex buffer layers in N2O ambient is reported. The electrical properties of grown oxide have been characterized using a metal-oxide-semiconductor structure. Fixed oxide charge density and mid-gap interface state density are found to be 6×1010 cm−2 and 1.2×1011 cm−2 eV−1, respectively. The oxide on strained-Si samples has exhibited hole trapping behavior and moderately low interface state generation on constant current stressing.

Characterization of Strained Epitaxial Si1–x Gex Films Grown using Gas Source Molecular Beam Epitaxy

Abstract: State-of-the-art silicon-germanium heteroepitaxy techniques are reviewed. Strained Si1–x Gex epitaxial films have been grown by Gas Source Molecular Beam Epitaxy (GSMBE) on p-Si. The films have bee...

Oxidation of strained Si in a microwave electron cyclotron resonance plasma

Abstract: Electron cyclotron resonance plasma oxidation of strained Si on relaxed Si1−xGex buffer layers in O2 ambient at room temperature is reported. The electrical properties of grown oxide have been characterized and compared with thermally grown oxides using a metal-oxide semiconductor structure. At a low field, the accumulation of holes in the buried Si1−xGex layer, due to the type-II band offset, has been observed. The experimental results from thermally grown oxides have been compared with the simulation results obtained using a heterostructure Poisson solver.

Pt/p-strained-Si Schottky diode characteristics at low temperature

Abstract: The Schottky barrier height and ideality factor of Pt on p-type strained Si (grown on a graded relaxed Si0.82Ge0.18 buffer layer) have been investigated in the temperature range (90–150 K) using the current-voltage characteristics and are found to be temperature dependent. While the ideality factor decreases with an increase in temperature, the barrier height increases. Simulation based on a drift-diffusion emission model has been used to explain the experimental results.

Schottky diode characteristics of Ti on strained-Si

Abstract: The Schottky barrier height and ideality factor of Ti on p-type strained-Si (grown on a graded relaxed Si0.82Ge0.18 buffer layer) were investigated in the temperature range 200–300 K using the current-voltage (I-V) characteristics and were found to be temperature dependent. While the ideality factor decreases with an increase in temperature, the barrier height increases.

Enhancement of drain current in vertical SiGe/Si PMOS transistors using novel CMOS technology

Abstract: CMOS devices are being scaled for density and speed. However, scaling gate length is impeded by lithographic technology and scaling device width is limited by low hole mobility in PMOS transistors. In vertical MOS transistors, however, lithography does not limit the channel length. Current drive in PMOS devices may also be increased by use of a SiGe channel. In fact, the hole mobility in strained SiGe normal to the growth plane is predicted to be significantly larger than in its unstrained counterpart. Therefore, we propose vertical Si/sub 1-x/Ge/sub x//Si PMOS and Si NMOS transistors and demonstrate (1) 100% increase of drive current in a vertical SiGe PMOS device, (2) the first experimental evidence of the enhancement of out-of-plane hole mobility in a vertical PMOSFET, and (3) experimental results for vertical NMOS devices, thus exhibiting the promise of vertical SiGe/Si CMOS.

Ultrathin Oxides on Strained Epitaxial Si1–xGex Films at Low Temperature

Abstract: Integration issues of SiGe strained layers in Si-technology-based integrated circuits are addressed. The present status of the silicon dioxide formation on SiGe films is reviewed. Results of our studies on the low temperature (150–200°C) growth of ultrathin oxides using microwave plasma (in both O2 and N2O ambient), compositional analysis, electrical characterization and interfacial properties of the oxides are presented. Hole confinement in a Gas Source Molecular Beam Epitaxy (GSMBE) grown Si0.74Ge0.26/Si quantum well on silicon using (i) computer simulation and (ii) C-V measurements are also demonstrated.

SiGe/Si vertical PMOSFET device design and fabrication

Abstract: As channel lengths shrink continuously to smaller dimensions in order to improve performance and packing density, lithography, isolation, power supply and short channel effects have proved to be major limitations. Recently vertical MOSFETs (VMOS), also known as surround gate transistors, or 3-D side- wall transistors have been shown to overcome these process limitations. In this paper, we review the various VMOS technologies and applications and compare the performance of these devices to planar devices. We also present a novel deep submicron vertical SiGe/Si PMOSFET fabricated by Ge implantation. The Ge was implanted in the Si vertical channel to form a strained SiGe layer to increase drive current in P channel devices. PMOS drive current can be increased by about 100% compared to Si control devices. Thus, this technology offers CMOS circuit designers the flexibility to match PMOS and NMOS current drive capabilities, which was previously limited by the difference in electron and hole mobilities in Si.

Schottky Barrier Height of Ti on Strained Layer Si/Si1–xGex Films

Abstract: The Schottky barrier height of Ti on p-type Si1–xGex/Si and Si have been investigated-in the temperature range 110–250 K using the current voltage technique. Rutherford Backscattering Spectroscopy ...