We investigate a multiple-gate GaAs-based nanowire field-effect transistor (FET) for detecting spatially distributed molecular charges. Spatial resolution is implemented to the nanowire by arranging narrow metal gate array. In this device the molecule charge position and the metal gate position are correlated through capacitive coupling between the molecule and a metal gate. Then a molecule charge in the gate periphery with appropriate gate biasing selectively reflects in the nanowire current. To demonstrate our concept, we fabricate a GaAs-based nanowire FET having a 50-nm-length Schottky gate array with 50-nm interval and investigate to arrange the charged molecules at arbitrary position using Tetraphenylporphyrin (TPP).
An alternative to the transistor for high-frequency detector applications is the two-terminal self-switching diode (SSD). The SSD is based on a nanometer-wide channels and a lateral gate connected to a drain. SSDs with In65Ga35As channels were fabricated and characterized. The design was optimized for low noise detection. In on-wafer measurements 2-315 GHz, a responsivity >150 V/W and noise-equivalent power (NEP) 50-100 pW/Hz½ was measured with a 50 Ω source. In the measured frequency range, this is the lowest NEP for SSDs demonstrated.
An heteroepitaxial bonded III-Von Si nanopatterned waveguide is demonstrating a wavelength selective behavior thanks to a super-periodicity added to its sub-wavelength, below band-gap, structuration. Effective Medium Theory has been implemented for modal effective index determination, allowing a quick and nevertheless detailed investigation of the role of a large number of geometrical parameters. Such nanostructured waveguides offer the versatility for designing complex geometries required for hybrid advanced optical functions on silicon.
Terahertz power dependence of the photoresponse of field effect transistors, operating at frequencies from 0.1 to 3 THz for incident radiation power density up to 100 kW/cm(2) was studied InGaAs high electron mobility transistors. The observed signal saturation behavior is explained by analogy with current saturation in standard direct currents output characteristics. The theoretical model of terahertz field effect transistor photoresponse was developed shows a good description match with experimental data. Our experimental results show that dynamic range of field effect transistors based terahertz detectors is very high and can extend from mW/cm(2) up to kW/cm(2).
We report a novel method for direct InP/SOI wafer bonding based on hydrophilic/hydrophobic treatment, which requires only a low annealing temperature of 320°C. Scanning acoustic microscope (SAM) measurements show that the proposed treatment helps form a firm bond between the wafer pair. The bonding strength is measured with a destructive approach, and the bonding interface is evaluated by scanning electron microscope (SEM).
This paper reports current gain and high-frequency characteristics of InP DHBTs with a passivation ledge and various emitter sizes. With the passivation ledge, current gain of over 40 is maintained even for a 0.25-μm-emitter HBT. The ft is over 420 GHz for HBTs with emitters ranging from 0.25 to 0.5 μm. On the other hand, the fmax greatly increases from 320 to 440 GHz with decreasing emitter width from 0.5 to 0.25 μm. These results indicate that the 0.25-μm-emitter HBT exhibits balanced high-frequency performance (ft= 449 GHz and fmax= 440 GHz) while maintaining a current gain of over 40.
We have successfully demonstrated epitaxial growth of an InP layer to fabricate an InGaAsP/InP buried heterostructure (BH) on Si substrate, in which a thin InGaAsP-based active layer is directly bonded to SiO 2 /Si substrate before fabricating the BH. An O 2 plasma-assisted wafer bonding is used to combine a 2-inch Si substrate with 1-μm thick thermal oxide and a 2-inch InP substrate with the active layer. We confirm that the crystal quality is not significantly degraded compared with that on InP substrate. These results indicate that the proposed fabrication method is suitable for integrating III-V materials on Si substrate.
We investigated the effects of introducing tertiary-butyl chloride (TBCl) on InP and InAsP nanowire growth for the purpose of improving the tapering shape. The InP nanowire length was increased by supplying TBCl at low flow rates, and decreased gradually by supplying it at high flow rates. The growth in the radial direction was effectively suppressed by using TBCl. InAsP nanowires were also grown with TBCl. We obtained long and less tapered structures with good crystal quality. Selectivity of Cl etching to InAs and InP is discussed.
We have investigated the effects of reactive gases used during the deep reactive ion etching process of InP-based photonic structures in an inductively-coupled plasma (ICP) reactor. Samples with a specific structure, including 9 InAsP/InP quantum wells (QW) with graded As/P composition, were designed. Different chlorine-based gas chemistries were tested. Characterization was performed using cathodo-Iuminescence (CL) and photo-luminescence (PL) at different temperatures, and secondary ion mass spectrometry (SIMS). The luminescence lines display a blue shift upon exposure to the reactive gases, and a strong spectral sharpening. We discuss the influence of Cl diffusion and thermal processes during etching on these modifications.
Using high quality, single crystalline InP nanowire grown on silicon substrate, we demonstrates sensitive avalanche photodiode with 26.6 A/W and bipolar junction phototransistor with 4 A/W integrated onto silicon substrate. The avalanche photodiode has unique radial p-n junction that allows it to reach a high avalanche gain of 100 at a low bias of 1 V. The bipolar junction phototransistor integrates a sensitive photodiode with a receiver circuit, creating a compact, monolithic receiver circuit for optical interconnect application. These devices are promising in bringing low energy, high bandwidth optical interconnects to silicon electronics.
We report on In0.63Ga0.37As FinFETs utilizing nanowires grown by selective-area growth as channel. These nanowires are defined by crystallographic planes rather than pattern transfer using etching. The fabricated devices exhibit maximum transconductance gm, max = 2.05 mS/um at Vds = 0.5 V, as well as record-high extrapolated ft = 300 GHz and fmax = 342 GHz, on the non-planar III-V MOSFET platform.
We present a method to prepare a mixed resist material composed of a positive electron-beam resist (ZEP520A) and C60 fullerene. The method is modified from previous methods in literatures to achieve an optimized mixing. An improvement of the mixed material on the thermal resistance respect to the same structures fabricated with normal ZEP resist has been demonstrated by fabricating multimode interference couplers and coupling regions of micro-ring resonators. An improvement on the propagation loss of the InP membrane waveguides from 6.6 to 3.3 dB/cm using this mixed material is also shown.
The nature of the ground optical transition in (In, Ga)As/GaP quantum dots is thoroughly investigated through k·p calculations and a supercell tight-binding simulation. Quantum dot morphology is deduced from scanning-tunneling-microscopy images. The strain field has a strong influence on the conduction band states. Indeed, for a pure GaAs QD, the wavefunction of the ground electron state is spatially confined in the GaP matrix, close to the dot apex, in a tensile strain region, having mainly Xz character. Time resolved and hydrostatic pressure photoluminescence experiments strongly support the theoretical conclusions. Promising results from the literature on (In, Ga)As/GaP quantum dot will be reviewed.
An ultralow-dc-power negative-differential-conductance (NDC) microwave amplifier using resonant tunneling diodes (RTDs) is presented and its noise figure characteristic is for the first time reported. The fabricated amplifier exhibits an extremely low dc-power consumption of 155 μW along with good RF performances of an RF gain of 8.1 dB, a return loss of more than 11 dB, and a noise figure of 4.5 dB at 5.5 GHz. The gain-to-dc power ratio was estimated to be 52.2 dB/mW. The figures-of-merit (FOMs) of the achieved gain-to-dc power ratio and noise figure are record for sub-mW low-power monolithic amplifiers at the related frequency band.
1.3μm Electroabsorption Modulated DFB Lasers (EMLs) operating at 45°C are presented for higher order intensity modulation formats. The application of Pulse Amplitude Modulation (PAM) is experimentally demonstrated for PAM4/PAM8 coding at symbol rates of 28 GBd. With integrated impedance matching the low cost EML shows an increased optical modulation bandwidth of 40 GHz. NRZ eyes at 56 Gb/s have been measured with dynamic extinction ratio of > 9 dB which demonstrates the potential of the devices for PAM at higher symbol rates. The EML performance is discussed for application in single channel solutions of direct detection 100G atacomm systems.
We show that heteroepitaxy of thin films of InP on Al0.48In0.52As by MOVPE does not result in continuous flat layer growth, but instead develops a number of low dimensional structures, e.g. quantum dots and rings. We consider local phase separation/alloying-induced strain and preferred aggregation of adatom species on the substrate surface together with reduced wettability of InP on AlInAs to be the cause of the observed surface organization. This behavior has not been previously reported, and it opens a new application window for creating strain-free type-II staggered QD structures for possible applications in optical memories, detectors, and solar cells.
For several compositions of In 1-x Ga x As y P 1-y lattice-matched to InP spectroscopic measurements were made. With the help of the Tanguy model, the refractive indices are calculated in the infrared transparent and absorption region. From these measurements general parameters for the Tanguy model are derived for the In 1-x Ga x As y P 1-y material system lattice-matched to InP.
We have demonstrated the operation of thin body GaSb-on-insulator (GaSb-OI) p-MOSFETs on Si wafers fabricated by direct wafer boding (DWB). We have developed a wafer-scale transfer technique for transferring ultrathin GaSb layers to Si wafers. We have found that the hole mobility of the thin body GaSb-OI p-MOSFETs depends on the GaSb thickness and the GaSb channel surface condition.
We report on multi-wavelength pump-probe characterization of the fundamental gain dynamics in recently developed InAs/InP quantum-dot semiconductor optical amplifiers. Recovery of the gain at various wavelengths following a powerful optical pump pulse, was recorded at different bias levels and different excitation powers. Wavelength dependencies of gain saturation depth, of the level to which the gain recovers and of the recovery rates were obtained. Unlike in quantum-dash amplifiers, these quantum-dots exhibit no instantaneous gain response, confirming their zero-dimensional nature.
We demonstrate an ultra-low threshold nanowire laser monolithically integrated on a (001) silicon substrate. By using a V-groove template we were able to reduce the laser threshold by one order of magnitude (0.19pJ per pulse) compared with our earlier devices and dramatically increased the yield throughout the wafer.
