Kikuo Makita

Si nano-photodiode with a surface plasmon antenna

We developed a Si nano-photodiode with a surface plasmon (SP) antenna for a SiON waveguide-integrated structure. We showed that interfacial periodic nano-scale metal-semiconductor-metal Schottky electrodes function as an SP optical antenna and also as an optical coupler between a SiON waveguide and a very thin Si-absorption layer.

High-speed and low-dark-current flip-chip InAlAs/InAlGaAs quaternary well superlattice APDs with 120 GHz gain-bandwidth product

High-speed flip-chip InAlAs/InAlGaAs quaternary well superlattice avalanche photodiodes grown by gas-source molecular beam epitaxy have been achieved with 120-GHz gain-bandwidth product. These photodiodes exhibit a maximum bandwidth of 15 GHz, 0.34- mu A dark current at a multiplication factor of 20, a capacitance of 0.17 pF, 65% quantum efficiency, and a low breakdown voltage of about 20 V. A clear eye opening at a multiplication factor of 20 was obtained for 10-Gbs nonreturn to zero signals. This indicates that these devices have potential for high-speed, high-sensitivity and low-power-consumption, long-wavelength optical receivers.<<ETX>>

Temperature dependence of impact ionization coefficients in InP

Impact ionization coefficients for electrons and holes in InP were measured experimentally at 25–175 °C in the 400–600 kV/cm electric field range with planar avalanche photodiodes, in which the n‐InP avalanche region was separated from the light absorbing InGaAs and/or InGaAsP layers. α and β monotonically decreased with elevated temperatures; β/α slightly decreased with increasing temperature. Comparison of the experimental results with Okuto–Crowell formula on the impact ionization coefficient gave the phonon energy ERO=46 meV and the phonon scattering mean free path λ0=41.7 A for electron impact ionization and ERO=36 meV and λ0=41.3 A for hole impact ionization, respectively. Curves calculated by using these parameters agree with the experimental results quite satisfactorily at each temperature.

Impact ionization rates in

Impact ionization rates for electrons and holes in

Single photoelectron trapping, storage, and detection in a field effect transistor

A single photoelectron can be trapped and its photoelectric charge detected by a source/drain channel in a transistor. Such a transistor photodetector can be useful for flagging the safe arrival of a photon in a quantum repeater. The electron trap can be photo-ionized and repeatedly reset for the arrival of successive individual photons. This single photoelectron transistor (SPT) operating at the lambda = 1.3 mu m tele-communication band, was demonstrated by using a windowed-gate double-quantum-well InGaAs/InAlAs/InP heterostructure that was designed to provide near-zero electron g-factor. The g-factor engineering allows selection rules that would convert a photons polarization to an electron spin polarization. The safe arrival of the photo-electric charge would trigger the commencement of the teleportation algorithm.

Planar-structure InP/InGaAsP/InGaAs avalanche photodiodes with preferential lateral extended guard ring for 1.0-1.6 mu m wavelength optical communication use

A planar InP-based InGaAs heterostructure avalanche photodiode (APD) with a preferential lateral extended guard ring is proposed. Optimum design and device fabrication are described for the planar-structure APD using various-donor-concentration n-InP avalanche layers, separated from the light-absorbing InGaAs layer. High performance results are low dark current, high speed, low noise, and uniform avalanche gain without edge breakdown. The APD yielded a sensitivity as high as -37.4 dBm for a 2-Gb/s 1.57- mu m wavelength return-to-zero sequence with 10/sup -9/ bit error rate. >

Electrical and optical interconnection for mechanically stacked multi-junction solar cells mediated by metal nanoparticle arrays

An interconnection approach for mechanical stacking of solar cells is described. In this approach, block copolymer-templated fabrication of metal nanoparticle arrays and van der Waals bonding were integrated to design interfaces which permit both high interfacial conductivities and minimal transmission losses upon interconnections of solar cells. A series of electrical and optical characterizations verified that the approach potentially provides resistances of as low as 3.7 Ω-cm2 with transmission losses of less than 2%. The demonstrative two-junction solar cell exhibited promising open-circuit voltage and fill factor, suggesting the possibility of achieving high-efficiency multi-junction solar cells based on this unique strategy.

Reliability of mesa-structure InAlGaAs-InAlAs superlattice avalanche photodiodes

Reliability tests of mesa-structure InAlGaAs-InAlAs superlattice avalanche photodiodes (SL-APDs) have been performed by accelerated aging at three different temperatures for the first time. The lifetime of the SL-APDs is estimated to be over 1.0/spl times/10/sup 5/ hours at 50/spl deg/C with a degradation activation energy of 1 eV. These results indicate that the SL-APDs have a reliable lifetime for 2.5-10 Gb/s LAN applications.

Gain-bandwidth product analysis of InAlGaAs-InAlAs superlattice avalanche photodiodes

The gain-bandwidth (GB) product of InAlAs-InAlGaAs quaternary well superlattice avalanche photodiodes (SL-APDs) has been analyzed by solving current-continuity equations including electron and hole impact ionization rates in a separate absorption and multiplication (SAM) structure. The results indicate that the GB product of InAlGaAs quaternary well SL-APDs can be increased to more than 150 GHz by decreasing the thickness of a p/sup +/-InP field buffer layer. This is due to reduced ionization in the p/sup +/-InP field buffer layer, which has an opposite ionization rate ratio compared to the superlattice. This analysis was experimentally confirmed by a GB product of 150 GHz for the SL-APDs with a 33.4 nm thick p/sup +/-InP field buffer layer. The GB product obtained is the largest value in III-V compound-semiconductor APDs, to our knowledge,.

High-speed, high-reliability planar-structure superlattice avalanche photodiodes for 10-Gb/s optical receivers

This paper reports the planar-structure InAl-GaAs-InAlAs superlattice avalanche photodiodes (SL-APDs) with a Ti-implanted guard-ring, which were developed for a compact and high-sensitivity 10-Gb/s optical receiver application. The design and fabrication of the novel concept planar-structure including the Ti-implanted guard-ring are described. The characteristics of the planar APDs are 0.36 /spl mu/A dark current at a multiplication factor of 10, 67% quantum efficiency, 110-GHz gain-bandwidth (GB) product, 15-GHz top-bandwidth, and - 27.2-dBm sensitivity at 10 Gb/s. The reliability was preliminary tested and the lifetime of longer than 10/sup 7/ h at 50/spl deg/C was estimated. The dark current characteristics including its temperature dependence and the excess noise characteristics are also analyzed. All the obtained characteristics exhibit the practical availability of the planar SL-APDs in the 10-Gb/s trunk line optical receiver uses.