Kaori Kurihara

High-speed optical switching of InAlGaAs/InAlAs multi-mode interference photonic switch with partial index-modulation region (MIPS-P)

A semiconductor multi-mode interference photonic switch with partial index-modulation regions (MIPS-P) was fabricated, and we demonstrated high-speed switching operation in a switching time of about 1.5 ns, for the first time, at a repetition rate of 10 MHz.

High-quality, 2-inch-diameter m-plane GaN substrates grown by hydride vapor phase epitaxy on acidic ammonothermal seeds

In this paper, we discusse the origin of basal-plane stacking faults (BSFs) generated in the homoepitaxial hydride vapor phase epitaxy (HVPE) growth of m-plane gallium nitride (GaN). We investigated the effects of seed quality, especially dislocation density, on BSF generation during homoepitaxy. The results clearly identify basal-plane dislocation in the seed as a cause of BSF generation. We realized high-quality m-plane GaN substrates with a 2-in. diameter using HVPE on low-dislocation-density m-plane seeds.

Vacancies in InxGa1−xN/GaN multiple quantum wells fabricated on m-plane GaN probed by a monoenergetic positron beam

Vacancy-type defects in InxGa1−xN/GaN multiple-quantum-well (MQW) structures fabricated on m-plane GaN by metal–organic chemical vapor deposition have been studied using a monoenergetic positron beam. Through measurements of Doppler broadening spectra of the annihilation radiation, the vacancy-type defects in MQW structures were probed. The positron trapping rate of defects decreased under photon illumination, which is attributed to the emission of electrons from those defects and/or the suppression of the positron diffusion by optically active defects. The energy level of the defects was close to the energy of photoluminescence emissions. The relationship between the energy width of the photoluminescence line and the defects is discussed.

Carbon-doped InAl(Ga)As with low oxygen contamination

Carbon doping in an InAl(Ga)As material system grown by LP-MOVPE has been studied. Reduction of oxygen in carbon-doped InAlAs has been demonstrated by investigating the incorporation mechanisms of carbon and oxygen, and the effect of removal of oxygen by bromine. Through use of these growth procedures, we have successfully made a C-doped InAlAs with low oxygen contamination for the first time. The electrical and optical characteristics of the C-doped InAlAs have been investigated. In the material with low oxygen incorporation, the p-type carrier density is almost the same as the carbon concentration. For optical properties, photo-luminescence measurements have revealed that reduction in oxygen is the key to achieving InAlAs layers with high optical quality. The results indicate that C-doped InAlAs crystals with low oxygen would be well worth using in laser structures.

Possible origin of double-peak emission in InGaN quantum wells on m-plane free-standing GaN substrates

A new theoretical model has been proposed to explain the origin of the double-peak emission observed characteristically in m-plane InGaN quantum wells (QWs). Although the emission spectrum with a double-peak structure is generally regarded as evidence of In compositional phase separation or extended crystal defects that generate localized energy states, such crystal irregularities cannot be observed by transmission electron microscopy or three-dimensional atom probe in the QWs. It has been clarified, by our model, that only the slowly decaying tailing of the density of states can cause the double-peak structure. This is consistent with experimental results, and furthermore, the measured temperature and In composition dependences of photoluminescence spectra with the double-peak emission can also be successfully reproduced by theoretical calculation based on our model.

High-Performance of InAlGaAs/InAlAs/InP Multi-Mode Interference Photonic Switch with Partial Index-Modulation Region (MIPS-P)

Introduction Advanced photonic networks in the next generation require high-speed switching with nano-second order switching time as well as low power consumption and low crosstalk, etc. For these purposes a semiconductor multi-mode interference photonic switch with partial index-modulation regions (MIPS-P) was proposed,[1][2] and we experimentally confirmed fundamental switching performances by using InAlGaAs/InAlAs, which is effective for efficient injected carrier confinement.[3][4] Here higher performances of InAlGaAs/InAlAs MIPS-P have been demonstrated under precise control of the fabrication and operation conditions to obtain lower crosstalk and higher-speed switching with even sub-ns switching time.