Quantum Wire Active Regions Research Articles

Evidence of two-dimensional lateral quantum confinement in self-formed core–shell InGaN nanowires on Si (111) emitting in the red

The proof of strong two-dimensional lateral quantum confinement in the In-rich core of red-light emitting self-formed core–shell InGaN nanowires is given. The nanowires are directly grown on Si (111) by plasma-assisted molecular beam epitaxy. After the initial InGaN nucleation, straight nanowires with quantum-size core radius determined by x-ray diffraction, transmission electron microscopy, and energy dispersive x-ray mappings develop. Detailed comparison of the photoluminescence from the core, the In contents of the core and shell, and the core radius with theoretical modeling reveals a parabolic confinement potential with large ground state quantum confinement energies of electrons and holes. Such strong lateral quantum confinement in a vertical quantum wire active region is ideal for the performance of optoelectronic devices, in particular of our reported red InGaN light emitting diode with high brightness and color stability.

Novel T-shaped GaSb/InAsN quantum wire for mid-infrared laser applications

In this work, we investigate GaSb/InAs1−xNx T-shaped quantum wire active region in mid-infrared laser. Multi-band k.p model and variational formalism are applied to find the confinement energies, the band structures, and optical gain. We then present a method of numerical calculation that is suited to any T-shaped quantum wire. By tuning the quantum wire thickness, the TE- and TM-polarized optical gain up to 21×103 cm−1 can be obtained for λ=3.11 μm at room temperature (RT), which is very promising to serve as an alternative active region for high-efficiency mid-infrared laser applications.

GaInAsP/InP long-wavelength lasers with strain-compensated quantum-wire active regions and SiO2/semiconductor reflectors

GaInAsP/InP strain-compensated multiple-quantum-wire lasers (wire widths of 19nm and 27nm in a period of 100nm) with SiO2/semiconductor reflectors were realized by electron-beam lithography, CH4/H2 reactive ion etching and two-step organometallic vapor-phase-epitaxial growth processes. As a result, the threshold current densities of these quantum-wire lasers were lower than those of quantum-film lasers prepared on the same initial wafer and oscillations from the transition between the ground levels were observed at room temperature.

Strained AlGaInP quantum wire lasers

We report on the fabrication of strained separate-confinement heterostructure AlGaInP visible laser diodes with multiple quantum wire active regions formed in situ during gas source molecular beam epitaxy. Lateral composition modulation with a period on the order of 100 Å perpendicular to the growth direction occurs spontaneously during the growth of the (GaP) 2/(InP) 2 short-period superlattice active region by the strain-induced lateral-layer ordering (SILO) process. Individual laser diodes fabricated from the same wafer but emitting parallel and normal to the wire axis exhibit highly anisotropic properties, including large difference in threshold current, emission wavelength, and opposite polarizations. These effects are explained in terms of the strained quantum wire potential. The additional degree of quantum confinement in quantum wire structure reduces the threshold current density by a factor of > 2.7 when compared with an otherwise identical quantum well laser.

Formation of Quantum Wires by Strain-Induced Lateral-Layer Ordering Process: Growth Mechanism and Device Applications

AbstractGaxIn1−xAs and GaxIn1−xP quantum wire (QWR) arrays were grown by a single-step molecular beam epitaxy. Lateral Ga(In composition modulation perpendicular to the growth direction occurs spontaneously during the growth of (GaAs)m/(InAs)n or (GaP)m/(InP)n shortperiod superlattices on InP or GaAs substrates, respectively, by the strain-induced lateral-layer ordering (SILO) process, producing lateral quantum wells. This straightforward method employs standard on-axis (001)-oriented substrates, and requires no pre-growth substrate patterning, nor does it involve post-growth processing for the formation of QWRs. Both GaxIn1−xAs infrared (1.7 μm) lasers and GaxIn1−xP visible (0.7 μm) lasers with QWR active regions have been successfully fabricated. These lasers showed many unique features that have never been observed in quantum well lasers.

Room-temperature operation of GaInAs/GaInAsP/InP SCH lasers with quantum-wire size active region

Improvements in the fabrication of GaInAs(P)/InP devices consisting of an ultrafine structure by using two-step organometallic vapor phase epitaxy (OMVPE) growth, electron beam exposure direct writing, and wet chemical etching are reported. This improved process achieved, for the first time, a room-temperature continuous-wave (CW) operation of GaInAs/InP quantum-wire lasers consisting of 5-nm-thick and 10-30-nm-wide vertically stacked triple quantum-wire active region within the period of 70 nm. A large blue shift of approximately 40 nm was observed in both the lasing and the electroluminescence spectra of Ga/sub 0.3/In/sub 0.7/As/InP compressively strained multi-quantum-well (MQW) wire lasers consisting of a 3-nm-thick and 30-60-nm-wide five-wire active region, which suggests a reduced effective mass of holes along the in-plane direction. >

AlGaInP multiple-quantum-wire lasers grown by gas source molecular beam epitaxy

GaxIn1−xP/Al0.15Ga0.35In0.5P graded-index separate-confinement heterostructure visible laser structures with multiple quantum wire active regions have been formed in situ during gas source molecular beam epitaxy. No regrowths or ex situ fabrication procedures were employed in the formation of the quantum wires. Quantum wires with cross-sectional dimensions of approximately 50×120 Å were routinely achieved with a linear density of 100/μm. Broad area stripe geometry lasers with contact stripe oriented in the [110] and [1̄10] directions exhibited anisotropic threshold current densities varying in ratio by a factor of more than 3.75. Threshold current densities as low as 400 A/cm2 were obtained for lasers with stripes in the [110] direction, perpendicular to the quantum wires. Strong dependence of electroluminescence polarization on stripe direction was also observed.

Spontaneous emission factor of a microcavity DBR surface emitting laser. II. Effects of electron quantum confinements

For pt.I see ibid., vol.27, p.1347-58 (1991). A method for the theoretical analysis of the spontaneous emission factor (C factor) has been developed for microcavity distributed Bragg reflector (DBR) surface emitting lasers having various quantum-well active regions. It is shown that the C factor can be enlarged by the enhancement of mode density, the anisotropic emission, and the narrow spectral width in quantum wells. C approximately 0.6 may be obtained with GaAs-AlAs DBRs, 0.55 mu m*0.55 mu m cross section of the cavity, three times vertically long cross section of quantum-wire active regions, and the spectral width of several nanometers at room temperature. This value can be further increased by utilizing a narrower spectral width expected at low temperature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Quantum wire lasers by OMCVD growth on nonplanar substrates

Abstract In this paper, we describe the progress made in the fabrication of quantum wire lasers using growth on nonplanar substrates as a lateral patterning technique. GaAs/AlGaAs quantum wire injection lasers with up to three crescent-spaped quantum wire active regions have been fabricated. The lowest threshold current of 2.4 mA was obtained for lasers with 2 quantum wires. We also report on two techniques for the fabrication of quantum wire arrays in GaAs/AlGaAs. Finally, we present our results on an attempt to fabricate quantum wire lasers based on InP, and propose possible solutions to the problems encountered.

Single quantum wire semiconductor lasers

Single quantum wire GaAs/AlGaAs injection lasers were fabricated using organometallic chemical vapor deposition on V-grooved GaAs substrates. The quantum wire active region has a crescent-shaped cross section ∼100 Å thick and less than 1000 Å wide. Amplified spontaneous emission and lasing spectra of the quantum wire lasers exhibit effects due to transitions between quasi-one-dimensional subbands separated by ∼10 meV. Single quantum wire laser structures with tight optical confinement exhibited threshold currents as low as 3.5 mA for uncoated devices at room temperature.