Dhanorm Plumwongrot

GaInAsP/InP Partially Strain-Compensated Multiple-Quantum-Wire Lasers Fabricated by Dry Etching and Regrowth Processes

This paper reports the structural properties and lasing characteristics of GaInAsP/InP multiple-quantum-wire lasers fabricated by electron beam lithography, CH4/H2-reactive ion etching and organometallic vapor-phase-epitaxial regrowth. Good size distributions of multiple-quantum-wire structures (wire widths of 18 nm and 27 nm in a period of 80 nm) have been obtained with standard deviations less than ±2 nm. We have confirmed that low-damage etched/regrown interfaces of quantum-wire structures can be realized by using a partially strain-compensated quantum-well structure. Threshold current densities of 5-quantum-well wirelike lasers (wire widths of 43 nm and 70 nm) were found to be lower than that of the quantum-film laser, fabricated from the same initial wafer, due to a volume effect at temperatures up to 85°C. Finally, room temperature (RT)-continuous wave (CW) operation of multiple-quantum-wire lasers (wire width of 23 nm in a period of 80 nm, 5-stacked quantum-wires) was achieved, and the good reliability of this quantum-wire laser was demonstrated for the first time by means of lifetime measurement under the RT-CW condition.

Loss Reduction of Si Wire Waveguide Fabricated by Edge-Enhancement Writing for Electron Beam Lithography and Reactive Ion Etching Using Double Layered Resist Mask with C60

Loss reduction methods for single-mode photonic wire in silicon-on-insulator were investigated, with a Si core size of 200×440 nm2, fabricated with electron beam lithography and dry etching, using a double layer of electron beam (EB) resist mask. The transverse electric (TE) mode propagation loss measured at a wavelength of 1550 nm was 4.5 dB/cm, which is, to the best of our knowledge, the lowest value ever attained for a Si wire waveguide fabricated by the parallel plate reactive ion etching (RIE) method.

Low-threshold-current operation of 1540 nm GaInAsP∕InP distributed-feedback lasers with multiple-quantum-wire active regions

1540 nm wavelength GaInAsP∕InP distributed-feedback lasers consisting of multiple-quantum-wire active regions with the wire width of 24 nm were realized by electron-beam lithography, CH4∕H2 reactive ion etching, and two-step organometallic vapor-phase-epitaxial growth processes. A threshold current as low as 2.7 mA (threshold current density=270A∕cm2), a differential quantum efficiency of 19%∕facet and a submode suppression ratio of 51 dB at a bias current of twice the threshold were achieved for the stripe width of 3.0μm and the cavity length of 330μm under a room-temperature continuous-wave condition.

High T0 Operation of 1590 nm GaInAsP/InP Quantum-Wire Distributed Feedback Lasers by Bragg Wavelength Detuning

1590 nm GaInAsP/InP quantum-wire distributed feedback lasers incorporating Bragg wavelength detuning from the gain peak wavelength of active regions were fabricated by electron beam lithography, CH4/H2 reactive ion etching, and organometallic vapor-phase-epitaxy regrowth. A stable single-mode operation was obtained over a wide temperature range for devices with a detuning amount of about 30–40 nm. In particular, a submode suppression ratio of 42 dB was achieved at 1.2 times the threshold. The characteristic temperature for the threshold current density of 95 K and that for the differential quantum efficiency of 243 K were obtained over a 20 to 80 °C temperature range.

Micro-photoluminescence characterizations of GaInAsP/InP single quantum wires fabricated by dry etching and regrowth

We characterized the micro-photoluminescence (micro-PL) of GaInAsP/InP single quantum wires (Q-wires) at 6 K. The Q-wires had 6–39-nm lateral widths and a 6-nm vertical thickness and were fabricated by dry etching and regrowth. Micro-PL spectra were clearly observed for all single Q-wires. The spectra revealed a high degree of uniformity along the Q-wires. The PL peak energy showed a systematic blueshift with the reduction of the Q-wire lateral width. The blueshift was attributed to the lateral quantum confinement and strain from a lateral direction, and was 100 meV in a 6-nm-wide Q-wire. Systematic analysis on the PL widths of the Q-wires showed that the PL spectra were broadened by fluctuations of 3 nm in the lateral width of the Q-wire after the dry etching and the regrowth in addition to the broadening caused by the fluctuation in the vertical thickness during the initial film growth and that caused by ion bombardment through a Ti metal mask in the dry etching process. The decreased PL intensities in ...

Low-Threshold Current Density GaInAsP/InP Quantum-Wire Distributed Feedback Lasers Fabricated by Low-Damage Processes

We demonstrate 1540-nm-wavelength GaInAsP/InP distributed feedback lasers, consisting of multiple-quantum-wire active regions with a wire width of 30 nm, fabricated by electron-beam lithography, CH4/H2 reactive ion etching, and two-step organometallic vapor-phase-epitaxial growth processes. By adopting low-damage fabrication processes for high-mesa stripe structures, a threshold current as low as 2.1 mA, which corresponds to a threshold current density of 176 A/cm2, and a differential quantum efficiency of 16%/facet were obtained under room-temperature continuous-wave conditions. A sub-mode suppression-ratio of 50 dB at a bias current of twice the threshold was also achieved.

Length dependence of in-plane polarizations anisotropy in GaInAsP/InP quantum-wire structures fabricated by dry etching and regrowth process

Wire-length dependences of In-place polarization anisotropy in GaInAsP/InP quantum-wire (Q-wire) structures fabricated by dry-etching and regrowth processes were investigated using a photo luminescence (PL) measurement. The reduction of polarization anisotropy of Q-wires is expected in the shorter Q-Wires. A strain-compensated GaInAsP/InP single-quantum-well initial wafer was prepared by an organometallic-vapor-phase-epitaxy (OMVPE) system. Using electron beam lithography, Ti-mask lift-off, CH4/H2 reactive-ion-etching and OMVPE regrowth processes, various lengths (L) of the Q-wires were realized for wire-widths (W) of 11-, 14- and 18 nm. The Q-wires were measured the polarization property in normal and parallel to wire-length direction at room temperature. As a result, stronger polarization anisotropy was observed in narrower Q-Wires and reduced in shorter length of Q-Wires. Furthermore, polarization anisotropy of strained Q-Wires was predicted by taking in account of the dipole moment interaction between conduction and heavy-hole subbands optical transition. A 5-nm narrowed wire-width calculation results shows a good agreement with experimental results. This could be considered that a strain distribution in the Q-Wire induced the energy band deformation at the edge of the Q-Wire, which reduced the effective wire-width to much narrower than the actual size observed by an SEM image.

Polarization Anisotropy of Spontaneous Emission Spectra in GaInAsP/InP Quantum-Wire Structures

The polarization properties of GaInAsP/InP single-quantum-well (SQW) quantum-wire (Q-Wire) structures fabricated by electron beam lithography, CH4/H2 reactive ion etching, and organometallic vapor-phase epitaxial regrowth have been investigated. Spontaneous emission spectra of the electrical field perpendicular and parallel to the Q-Wire direction were measured and the polarization anisotropic properties in lattice-matched (LM) and strain-compensated (SC) SQW Q-Wire structures were compared. Even for a relatively wide wire around 35 nm, the polarization degrees in the SC-SQW Q-Wires were clearly observed to be three-times-stronger than in the LM-SQW Q-Wires. Furthermore, the wire-width dependences of the polarization degree in the LM- and SC-SQW Q-Wire structures were measured and compared with theoretical calculations. It was found that the theoretical prediction accurately fitted in the case of the LM-SQW Q-Wires, whereas the measured results showed approximately two-times-stronger polarization anisotropy than the prediction of the SC-SQW Q-Wires, which might be attributed to the energy band deformation and the effective wire-width becoming narrower than the wire-width measured from a scanning electron microscope (SEM) image.

Bragg Wavelength Detuning in GaInAsP/InP Distributed Feedback Lasers with Wirelike Active Regions

By adopting a relatively large amount (54 nm) of Bragg wavelength detuning from the gain peak wavelength of active regions, temperature dependences of threshold current density and differential quantum efficiency were markedly improved in a GaInAsP/InP distributed feedback laser with wirelike active regions emitting at 1600 nm. A stable single-longitudinal-mode operation with a sub-mode suppression ratio of 51 dB (at a bias current of 2 times the threshold) was obtained at room temperature. Variations of threshold current density and differential quantum efficiency between 10 and 85 °C were reduced to as low as ±19 and ±24%, respectively; hence, the variation of the operating current required for a certain output power in this temperature range was reduced to 1/2 to 1/3 of that without Bragg wavelength detuning.

RIE-plasma induced optical property degradation in GaInAsP/InP quantum-well structures

The origin and model of the time dependence of RIE-plasma induced optical property degradation of GaInAsP/InP quantum-well structures were investigated. Non-radiative recombination was enhanced by irradiating CH4/H2-plasma, and was found to be recovered during high temperature annealing in the embedding growth by organometallic vapor-phase-epitaxy.