A Power-Efficient High-Throughput 32-Thread SPARC Processor

This first generation of "Niagara" SPARC processors implements a power-efficient Chip Multi-Threading (CMT) architecture which maximizes overall throughput performance for commercial workloads. The target performance is achieved by exploiting high bandwidth rather than high frequency, thereby reducing hardware complexity and power. The UltraSPARC T1 processor combines eight four-threaded 64-b cores, a floating-point unit, a high-bandwidth interconnect crossbar, a shared 3-MB L2 Cache, four DDR2 DRAM interfaces, and a system interface unit. Power and thermal monitoring techniques further enhance CMT performance benefits, increasing overall chip reliability. The 378-mm² die is fabricated in Texas Instrument's 90-nm CMOS technology with nine layers of copper interconnect. The chip contains 279 million transistors and consumes a maximum of 63 W at 1.2 GHz and 1.2 V. Key functional units employ special circuit techniques to provide the high bandwidth required by a CMT architecture while optimizing power and silicon area. These include a highly integrated integer register file, a high-bandwidth interconnect crossbar, the shared L2 cache, and the IO subsystem. Key aspects of the physical design methodology are also discussed     

Resistive switching characteristics of ultra-thin TiOx

We investigated the resistive switching characteristics of Ir/TiO_x/TiN structure with 50 nm active area. We successfully formed ultra-thin (4 nm) TiO_x active layer using oxidation process of TiN BE, which was confirmed by X-ray Photoelectron Spectroscopy (XPS) depth profiling. Compared to large area device (50 μm), which shows only ohmic behavior, 250 and 50 nm devices show very stable resistive switching characteristics. Due to the formation and rupture of oxygen vacancies induced conductive filament at Ir and TiO_x interface, bipolar resistive switching was occurred. We obtained excellent switching endurance up to 10⁶ times with 100 ns pulse and negligible degradation of each resistance state at 85 °C up to 10⁴ s.     

Ultra-low temperature sensitive deep-well quantum cascade lasers (λ - 4.8 μm) via uptapering conduction band edge of injector region

A new design feature for deep-well quantum cascade (QC) lasers, in which the conduction band edge of the injector region is uptapered, results in virtual suppression of carrier leakage out of the active regions of 4.8 mm emitting devices. For heatsink temperatures in the 20?90°C range the characteristic temperature coefficients for threshold, T₀, and slope efficiency, T₁, reach values as high as 278 and 285 K, respectively, which are nearly twice the values for conventional QC lasers. At 20°C, the threshold current density for uncoated, 30 period, 3 mm-long devices is only ~1.8 kA/cm².     

Energy Loss Mechanism in Organic and Inorganic Light-Emitting Diodes

We report that there exists a similar energy loss mechanism in fluorescent/phosphorescent organic light-emitting diodes (F/P OLEDs) and inorganic semiconductor optoelectronic devices [1310-nm InGaAsP-InP superluminescent diodes (SLDs)]. The loss of energy in inorganic SLDs based on thickness-altered asymmetric multiple quantum-well (QW) structures occurs depending sensitively on the sequence of QWs, an analogous behavior also observed in F/P OLEDs depending on the sequence of phosphorescent dopants for different colors. It is shown that such an energy (power) loss is evitable by placing long-wavelength QWs near the p-side in inorganic SLDs and similarly long-wavelength phosphors near the hole-transporting layer in F/P OLEDs.     

Generalized construction of binary bent sequences with optimal correlation property

We generalize the construction method of the family of binary bent sequences introduced by Olsen, Scholtz, and Welch (1982) to obtain a family of generalized binary bent sequences with optimal correlation and balance property by using the modified trace transform. Then, the conventional binary bent sequence becomes a special case of our construction method. Several families of the generalized binary bent sequences are constructed by using the bent functions on the intermediate field. Using some of the generalized binary bent sequences, new families of binary sequences with optimal correlation and balance property can be constructed by the lifting idea similar to No (1988) sequences, which are referred to as binary bent-lifted sequences.     

Variable structure observer of mismatched uncertain dynamical systems

To improve the steady state estimation error due to mismatched uncertainty, a variable structure observer for mismatched uncertain dynamical systems is proposed by using the generalised matrix inverse. Simulation results show that the estimation error is largely decreasing using the proposed observer.<>     

Electrical and optical properties of deep-red top-surface-emittinglasers

By studying thermal behavior of all-MBE surface-emitting lasers, barrier heights and optimum cavity design parameters are obtained. The barrier heights for holes between hetero-interfaces of Al_0.3Ga_0.7As-Al_0.65Ga_0.35As and AlAs-Al_0.65Ga_0.35As (Δx=-0.35) are measured to be 77 meV at zero bias for the deep-red top-surface-emitting laser. The barrier height decreases linearly with forward bias voltage, explaining the nonlinearity in current-voltage characteristics of the top-surface-emitting laser. The contribution of electrons to electrical resistance is estimated to be negligibly small compared to that of holes for the structure consisting of Δ_x =0.35. Minimum threshold current and maximum differential quantum efficiency observed around 200 K indicate slight mismatch between gain maximum and Fabry-Perot resonance for the deep-red top-surface-emitting laser