Current Confinement Structure Research Articles

Introduction of AlInAs-oxide current-confinement structure into GaInAsP/SOI hybrid Fabry–Pérot laser

An AlInAs-oxide current-confinement structure was introduced into a III–V/Si-on-insulator (SOI) hybrid laser for realizing an efficient light source composed of III–V/Si hybrid photonic integrated circuits. Lasing of the hybrid Fabry–Pérot laser was confirmed after introduction of the confinement structure providing both optical and electrical confinement. We determined the lasing characteristics of the designed hybrid laser, which showed a low threshold current and high external differential quantum efficiency comparable to that of conventional lasers fabricated on III–V compound semiconductor wafers. Comparison of the photoluminescence spectra of the III–V/SOI hybrid wafers before and after the process proved that oxidation had no influence on the active layer. The threshold current and external differential quantum efficiency of the fabricated laser with a stripe width of 4.5 µm and cavity length of 500 µm were obtained as 50 mA and 11%/facet, respectively.

Current Confinement Effect of InGaN Devices by Forming Photoelectrochemical-Oxidized GaN Nanoporous Structures

Aperture of InGaN light emitting diode (LED) structure was demonstrated by forming oxidized GaN nanoporous structure bellow the InGaN active layer. The fabricated processes consisted of a laser drilling hole process, a photoelectrochemical (PEC) lateral etching process, and a oxidation process. The LED structures consisted of a 30nm-thick GaN buffer layer, a 2μm-thick undoped GaN layer, a 2μm-thick n-type GaN layer, 0.7μm-thick current blocking layers, 10 pairs of the InGaN/GaN multiple quantum wells (MQWs) active layers, and a 0.2μm-thick magnesium-doped p-type GaN layer. 0.1μm u-GaN/0.5μm n-GaN:Si/0.1μm u-GaN layers were designed as current blocking layers for PEC processes. The current block layer The active layers consisted of a 30Å-thick InGaN-well layer and a 70Å-thick GaN-barrier layer. High resistance oxidized GaN nanoporous structure was formed embedded the LED structure that the injection current can confine in an aperture region. The aperture regions of the InGaN devices were observed clearly in optical and scanning electron microscopy (SEM) images. The peak photoluminescence (PL) spectra of the InGaN active layers were measured at 439.5nm and 435.6nm without and with embedded oxidized GaN nanoporous structure, respectively. The oxidized GaN nanoporous structure acted a current confinement structure that has potential for vertical cavity surface emitting laser applications.

Fabrication and analysis of current confinement structure for photonic crystal laser

AbstractWe recently proposed a laser structure with a circularly arranged cavity structure with AlOx with the aim of fabricating an electrically driven photonic crystal (PC) laser. Fabricating our proposed laser requires carrier injection to the cavity. In this study, we fabricated and investigated the current confinement structure for our proposed PC laser and established a process for fabricating the structure. We were able to apply current to a funnel and measure the current‐voltage characteristics of the structure. The electrical characteristics showed an ohmic feature, showing the possibility of fabricating our proposed PC laser. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Current‐Confinement Structure and Extremely High Current Density in Organic Light‐Emitting Transistors

Extremely high current densities are realized in single-crystal ambipolar light-emitting transistors using an electron-injection buffer layer and a current-confinement structure via laser etching. Moreover, a linear increase in the luminance was observed at current densities of up to 1 kA cm(-2) , which is an efficiency-preservation improvement of three orders of magnitude over conventional organic light-emitting diodes (OLEDs) at high current densities.

All-Optical Flip-Flop Operation at 1-mA Bias Current in Polarization Bistable Vertical-Cavity Surface-Emitting Lasers With an Oxide Confinement Structure

Polarization bistable vertical-cavity surface-emitting lasers (VCSELs) with an oxidation confinement structure were fabricated for low power consumption operation. Threshold current of the VCSEL was reduced to 0.22 mA. The VCSEL operated in a single longitudinal and transverse mode and in one of two orthogonal linear polarization modes. All-optical flip-flop operation based on polarization bistability was achieved at a record low bias current of 1.15 mA, which is about one tenth of our previously developed polarization bistable VCSEL without a current confinement structure.

Ridge Semiconductor Laser with Laterally Undercut Etched Current Confinement Structure

In this paper we modeled and analyzed the ridge type InGaAlAs/InP semiconductor laser with lateral current confinement structure, and optimized the design for the ridge wave guide with the current confinement. We proposed and fabricated the ridge type InGaAlAs/InP laser with a cost effective selective undercut etching method and demonstrated the improvement of the ridge laser performance. This paper provides a solution to solve the cost/yield issue for conventional BH (buried hetero-structure) type laser and performance issue for conventional ridge type laser.

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A red point source LED (Red-PSL) for optical encoders has been successfully developed. It has an AlGaInP MQW active layer and a DBR on a GaAs substrate grown by metalorganic chemical vapor deposition. A current confinement structure is formed by H+ implantation, which realizes a small emitting window of 40 μm×150 μm. Since high output power of 0.6mW at 20mA and high reliability were simultaneously achieved in a small emitting window PSL, the Red-PSL is suitable for high resolution optical encoders.

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ＩｎＧａＡｓ／ＡｌＧａＡｓ ＭＱＷ電流狭窄型ＬＥＤの低劣化挙動

Tunnel Junction for Long-Wavelength Vertical-Cavity Surface-Emitting Lasers

To improve the performance of long-wavelength vertical-cavity surface-emitting lasers (VCSELs), we performed an extensive study of tunnel junctions for current injection and confinement. The introduction of a tunnel junction in long-wavelength VCSELs can substantially improve the current injection scheme, because an n-type material is utilized in the p-side region by inserting a tunnel junction. We fabricated long-wavelength lasers with a tunnel junction formed by metalorganic chemical vapor deposition (MOCVD) using tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBAs), and confirmed the current homogenization effect. We also proposed and fabricated a current confinement structure by means of a simple fabrication process using a tunnel junction, i.e., the automatically formed tunneling aperture (AFTA). The AFTA has a tunnel junction aperture and can be formed automatically during electrode thermal annealing. We investigated the formation condition of the AFTA by varying the annealing temperature and time. We performed secondary ion mass spectroscopy (SIMS) and tunneling electron microscopy (TEM) of an annealed tunnel junction in order to understand the formation of AFTA.

Self-aligned current confinement structure using AlAs/InP tunnel junction in GaInAsP/InP semiconductor lasers

We propose a current confinement structure which can be self-formed by thermal annealing of a electrode metal with a self-aligning process. The migrated metal selectively destroys an AlAs/InP tunnel junction to form a high resistance isolation layer. The hole current can be injected through a preserved tunnel junction window. We confirmed its lateral confinement effect from the near-field pattern of fabricated GaInAsP/InP stripe lasers. The proposed current confinement structure is very simple and useful for the lateral injection in semiconductor optical devices including long-wavelength vertical-cavity surface-emitting lasers.

Super-lattice AlAs/AlInAs for lateral-oxide current confinement in InP-based lasers

We propose a novel super-lattice AlAs/AlInAs lateral-oxide current confinement structure for InP-based semiconductor lasers, including surface emitting lasers and opto-electronic devices. We also demonstrate an oxide current confined AlGaInAs/InP multi-quantum well edge emitting laser at 1.55 μm. The lasers can be fabricated by a single step MOCVD growth followed by a lateral oxidation. A tensile-strained AlAs layer on InP substrate has a large hetero-barrier and works as an electron stopping layer in p-type region. The optimized super-lattice AlAs/AlInAs layer exhibited no defects in spite of thick AlAs layer growth beyond critical thickness. In the super-lattice, AlAs layers are carbon-δ-doped for low turn-on voltage, between which narrow gap AlGaInAs layers are inserted for reducing resistance. Broad area lasers with the super-lattice structure exhibited a threshold current density of 130 A/cm 2 per well and characteristic temperature of 85 K.

GaInAs/AlGaInAs Semiconductor Lasers with AlAs Oxide Current Confinement Structure

An AlAs oxide current confinement structure based on an InP substrate has been demonstrated for the first time to realize low threshold long wavelength surface emitting lasers. The oxidized width is confirmed to be well controllable by choosing suitable oxidation time and temperature. We fabricated an metalorganic chemical vapor deposition (MOCVD) grown 1.65-µ m wavelength GaInAs/AlGaInAs multiple quantum well (MQW) edge emitting laser with the AlAs-oxide confinement structure of 3 µ m-wide and 15 µ m-wide windows. A 3 µ m-wide window oxidized laser having uncoated facets exhibits a threshold of 51 mA for device with a 800-µ m-long cavity. We have obtained a threshold current density of 1.3 kA/cm2 for 3 µ m-wide window devices. The results show a potential application of the proposed structure for low threshold long-wavelength surface emitting lasers.

Direct Patterning of the Current Confinement Structure for p-Type Column-III Nitrides by Low-Energy Electron Beam Irradiation Treatment

Partial low-energy electron beam irradiation (LEEBI) treatment was used to fabricate UV/blue light-emitting devices based on column-III nitrides having a directly patterned current confinement structure. The newly developed devices show very low leakage reverse current, stable operation at high pulsed current injection, and strong and narrow violet emission at room temperature.

Lateral npn junction and semi-insulating GaAs current confinement structure for index-guided InGaAs/AlGaAs lasers by molecular beam epitaxy

A current confinement structure with a lateral npn junction and a semi-insulating (SI) GaAs is examined for an index-guided InGaAs/AlGaAs strained quantum-well laser. Amphoteric doping of Si in GaAs and AlGaAs is used to form a lateral npn structure grown over a channeled patterned low-temperature-grown SI GaAs layer. A threshold current of 7.4 mA and total external differential quantum efficiency of 59% under room-temperature continuous-wave (CW) operation are achieved with devices fabricated by a self-aligned process. A device with antireflection-high-reflection (AR-HR) coating had a light output over 300 mW.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

InGaAs/AlGaAs strained quantum well laser with semi-insulating low temperature GaAs and lateral n-p-n current confinement structures grown by molecular beam epitaxy

A combination of a lateral n-p-n junction using an amphoteric doping of Si in GaAs and a semi-insulating GaAs grown at low temperature is applied for the first time to a novel current confinement structure for an index-guided InGaAs strained quantum well laser grown by two-step molecular beam epitaxy. A threshold current of 7.4 mA and total external differential quantum efficiency of 59% under room temperature continuous wave operation are achieved with devices fabricated by a self-aligned process.

Low threshold InGaAs strained quantum well laser with lateral npn current blocking structure grown by molecular beam epitaxy

A sophisticated current confinement structure using the amphoteric nature of MBE grown Si-doped GaAs and AlGaAs is demonstrated for an index-guided InGaAs strained quantum well laser. Lateral and vertical npn current blocking layers were formed for the first time by a selfaligned process. Devices showed threshold current of 10 mA and total slope efficiency of 0.56 under room temperature CW operation.

High-power and high-speed 1.3 μm V-grooved inner-stripe lasers with new semi-insulating current confinement structures on p-InP substrates

A significant improvement in the maximum output power of a 1.3 μm GaInAsP/InP laser with a semi-insulating current confinement structure is reported. The improvement has been achieved by interposing an n-type InP layer between a p-InP substrate and an Fe-doped InP layer. A maximum cw output power of 180 mW and a modulation bandwidth of 8.5 GHz have been obtained.

High-power operation of 830-nm AlGaAs laser diodes

We have developed a high-power, semicylindrical-shaped waveguide inner stripe laser diode (SCILD) using a current confinement structure. The structure is optimized for high-power operation without catastrophic optical damage (COD) which limits the maximum available optical power. We confirm that the optical electric field shape in the LD waveguide layer obtained from our analysis coincides with the micrograph of the COD on the device facet. The SCILD is emitted in the fundamental transverse mode up to 190 mW. The full beam angles between the half-power points were 10° and 30° in the directions parallel and perpendicular to the junction plane, respectively. The characteristic temperature of the threshold current was 152 K.

InGaAsP InP current confinement mesa substrate buried heterostructure laser diode fabricated by one-step liquid-phase epitaxy

New InGaAsP/InP buried heterostructure laser diodes fabricated by one-step liquid-phase epitaxy are described, in which the InGaAsP active region completely embedded in InP is grown on the top of the mesa stripe formed on the InP substrate while, simultaneously, current confinement structure is automatically formed on both sides of the mesa stripe. These current confinement mesa substrate buried heterostructure laser diodes (CCM-LD's) have current confinement structure which very effectively blocks unwanted leakage current bypassing the light emitting region which has enabled laser operation with a threshold current as low as 20 mA, 70-mW maximum CW output at room temperature, and 125°C maximum CW operation temperature. Life tests over 6000-h CW operation at 70°C and 5 mW/facet have confirmed good reliability of these devices.

Double-channel planar buried-heterostructure laser diode with effective current confinement

An InGaAsP double-channel planar buried-heterostructure laser diode has been developed in which a p-n-p-n current confinement structure effectively reduces the leakage current. High-power operation over 50 mW and high-temperature operation up to 130°C have been attained.