Low Threshold Current Density Operation Research Articles

Low Threshold Current Density Operation of a GaInAsP/Si Hybrid Laser Prepared by Low-Temperature N2 Plasma Activated Bonding

The integration of III–V active devices on a Si platform utilizing direct bonding is an attractive way to realize large-scale photonic integrated circuits. Because plasma activated bonding (PAB) is expected to have a higher bonding strength at a lower heating temperature as compared to conventional bonding methods, PAB is attractive for the reduction of non-radiative recombination centers in the III–V active region caused by thermal expansion during the bonding process. A GaInAsP/Si hybrid laser was fabricated with low-temperature (150 °C) N2 PAB, and a low threshold current density of 850 A/cm2 (170 A/cm2 per quantum well) was obtained.

Low Threshold Current Density Operation of Strain-CompensatedQuantum Cascade Laser

We report the low threshold current density operation of strain-compensatedIn0.64Ga0.36As/In0.38Al0.62As quantumcascade lasers emitting near 4.94 μm. By employing an enlargedstrain-compensated structure and optimizing the injector dopingdensity, a rather low threshold current density of 0.57 kA/cm2 at80 K is achieved for an uncoated 20-μm-wide and 2.5-mm-long laser.

Low threshold distribution feedback quantum cascade lasers at 7.6 μm grown by gas source molecular beam epitaxy

We have demonstrated the first Gas source molecular beam epitaxy (GSMBE) grown distributed feedback quantum cascade laser (DFB QC-laser) laser with low threshold current density operation at 7.6 μm. High quality DFB QC-laser heterostructures were grown by an one step GSMBE growth procedure. The first-order grating was defined by a holographic technology. A tunable single mode DFB QC-laser operation in pulsed mode with a low threshold current density of 574 A/cm 2 and a peak optical power of 50 mW at 70 K and 7.6 μm have been obtained. The side mode suppression ratio and the maximum single mode wavelength tuning range by changing their heat sink temperature are 23 dB and 20 nm, respectively.

Very low threshold current density operation of 1.5 [micro sign]m DFB lasers with wire-like active regions

Very low threshold 1.5 µm-wavelength GaInAsP/InP distributed feedback lasers consisting of deeply etched double quantum-well wire-like active regions have been successfully realised by CH4/H2 reactive ion etching and metal organic vapour phase epitaxial regrowth. A threshold current density Jth of as low as 94 A/cm2 was achieved for an active region width of 115 nm and cavity length of 600 µm.

Low threshold current density operation of GaInNAs quantum well lasers grown by metalorganic chemical vapour deposition

A metal organic chemical vapour deposition grown GaInNAs quantum well laser emitting at 1.25 µm is reported. The lowest threshold current density obtained by 50 µm wide stripe lasers was 340 A/cm2 for a cavity length of 1420 µm, which is almost comparable to the lowest value reported for GaInNAs lasers grown by molecular beam epitaxy. The threshold current density per well was 170 A/cm2, which is the lowest threshold value reported to date.

1.3 [micro sign]m GaAs-based laser using quantum dots obtained by activated spinodal decomposition

Low threshold current density (Jth = 65 A/cm2) operation near 1.3 µm at room temperature (RT) is realised for lasers using InAs/InGaAs/GaAs quantum dots (QDs). The lasing occurs via the QD ground state for cavity length L > 1 mm. The differential efficiency is 40% and internal losses are 1.5 cm–1. The characteristic temperature near RT is 160 K.

Ordered arrays of quantum dots: Formation, electronic spectra, relaxation phenomena, lasing

Elastic relaxation on facet edges, renormalization of the surface energy of the facets, and interaction between islands via the strained substrate are the driving forces for self-organization of ordered arrays of uniform coherent three-dimensional islands on crystal surfaces. For a (100) surface of a cubic crystal, two-dimensional square lattice of pyramid-like islands (quantum dots) with the periodicity along the directions of the lowest stiffness [010] and [001] has the minimum energy among different one-dimensional and two-dimensional arrays. For the InAs GaAs(100) system, an equilibrium array of dots of the lateral size ∼ 120–140 Å exists in a fixed range of growth parameters. The main luminescence peak at 1.1 eV, as well as peaks of excited states coincide in energy with the peaks revealed in the calorimetric absorption spectra regardless of the amount of InAs deposited (2–5 ML). Raman spectra indicate significant strain in InAs dots. The “phonon bottleneck” effect is bypassed via multi-phonon exciton and carrier relaxation. Ultranarrow lines (>0.15 meV) are observed in cathodoluminescence spectra up to high temperatures. Low threshold current density operation via zero-dimensional states and ultrahigh temperature stability of the threshold current ( T 0=450 K) are realized for a quantum dot injection laser. Increase in the gain and significant reduction in the radiative lifetime are possible via the self-organization of vertically-coupled quantum dots (VECODs) arranged in a well ordered artificial three-dimensional tetragonal lattice.

Low threshold current density operation of GaInAsP-InP laser with multiple reflector microcavities

We propose and demonstrate a new type of semiconductor laser having multiple reflector microcavities for the purpose of low threshold current operation. Very uniform multiple reflector microcavity structure was fabricated by electron beam (EB) lithography and selective wet chemical etching. Due to multiple reflection effect, threshold current density as low as 310 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (threshold current of 30 mA) was obtained at room temperature with the total cavity length of 64 μm and the cavity width of 200 μm.

Low threshold current density operation of GaInP-AlGaInP visible multiple quantum wire-like lasers (MQWR-LDs) under the room temperature pulsed condition

GaInP-AlGaInP multiple quantum wire-like layers were fabricated by the in situ strain induced lateral layer ordering process during MBE growth. According to TEM images, the quantum wire size was around 10 nm and quantum wire axis was along [011~] direction. When we made laser diodes with stripes along [011] direction, the low threshold current density, of 315 A/cm/sup 2/ was obtained. Anisotropic lasing characteristics between [011] and [011~] directions, in threshold current density, lasing mode, and lasing wavelength were observed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Substrate Misorientation, Multi‐Quantum‐Barrier, and Thermal Annealing Effects in MgZnSSe and ZnCdSe Compounds and Blue‐Green II‐VI Light Emitting Devices

AbstractMulti‐quantum‐barrier (MQB), substrate misorientation, and thermal annealing effects are investigated in MgZnSSe and ZnCdSe compounds and blue‐green II‐VI light emitting devices. The heterobarrier enhancement of MgZnSSe/ZnSe MQBs is analyzed to be 100 meV, using the experimental band offset of ΔEc ≈ 0.65ΔEg. By use of MQB effect, low threshold current density operation below 1 kA/cm2 can be expected in 480 nm blue emission ZnCdSe/MgZnSSe lasers. For N‐doped MgZnSSe grown on intentionally misoriented GaAs substrates, the decreased net acceptor concentration with misorientation angle is discussed, concluding that the enhanced sulfur incorporation by substrate misorientation plays some role in degradation. It is clarified that ZnSe and ZnSSe are not degraded up to 400°C annealing, while MgZnSSe is even at 350 to 400°C annealing. The light output of ZnCdSe/ZnSe MQW LEDs is enhanced by thermal annealing (325°C, 7 min), by a factor of three.

Pulsed room-temperature operation of a blue-green ZnSe quantum-well diode laser

Low-threshold current density operation has been obtained from (Zn, Cd)Se/Zn(S, Se) quantum-well diode lasers in the blue-green spectrum. The devices, with reflective facet coatings, have been operated at room temperature under pulsed conditions with threshold current densities of I(th) approximately 1 kA/cm(2).

Wide operating wavelength range and low threshold current In/sub 0.24/Ga/sub 0.76/As/GaAs vertical-cavity surface-emitting lasers

Very low threshold current density operation of triple quantum well vertical-cavity surface-emitting lasers (VCSELs) is reported. The active wells are strained In/sub 0.24/Ga/sub 0.76/As in GaAs. Devices from the same wafer operate at room temperature over a wavelength range of 958-1042 nm, with a minimum threshold current density of 366 A-cm/sup -2/ at 1018 nm. The dependence of threshold current on wavelength gives an insight into the optical gain spectrum of the quantum wells. It was shown that 50- mu m-diameter devices operate CW without heatsinking. >

Low threshold current density (760 A/cm2) and high power (45 mW) operation of strained Ga0.42In0.58P multiquantum well laser diodes emitting at 632 nm

A record low threshold current density of 760 A/cm2 has been obtained for a compressively strained multiquantum well laser emitting at 632 nm. Narrow stripe gain guided lasers show a maximum continuous output power of 45 mW with normally passivated mirrors. Stable laser operation over more than 3000 h at 40°C and 2 mW output power is reported for the first time.

Low (2.0 kA/cm2) threshold current density operation of 629 nm GaInP/AlInP multiquantum well lasers grown by gas source molecular beam epitaxy on 15° off (100) GaAs substrates

Very low threshold current density operation of 630 nm wavelength range GalnP/AllnP multiquantum well (MQW) lasers grown by gas source molecular beam epitaxy has been achieved. The reduction of threshold current density Jth was obtained by use of 15° off (100) toward [011] GaAs substrates, with a minimum Jth of 2.0 kA/cm2 at 629 nm. The Jth of the lasers grown on the exact oriented (100) substrates was 2.9 kA/cm2 at minimum, which was about 1.4 times larger than the above value.

Remarkable reduction of threshold current density of 670 nm GaInAsP/AlGaAs visible lasers by increasing al content of AlGaAs cladding layers

Extremely low threshold current density operation of the LPE grown 670 nm GaInAsP/AlGaAs lasers has been realised with drastic improvement of the characteristic temperature of the threshold from 45 K to 90 K by increasing the Al content of the AlGaAs cladding layers from 0.7 to 0.95. The threshold current density was 1.7 kA/cm2, about onethird of the previously reported value of 5–6 kA/cm2.

Record low-threshold, single-strained-quantum-well, graded-index, separate-confinement heterostructure laser

Record low-threshold current density operation of a singlestrained-quantum-well graded-index separate-confinement heterostructure GaInAs/AlGaAs laser has been obtained. The device was grown by molecular-beam epitaxy on a GaAs substrate and uses a proton implant stripe geometry to achieve a threshold current density of 1.3 kA/cm2.

Optimisation of four-and five-layer Alx Ga1−x As/GaAs large optical cavity lasers for high power, low threshold current density operation

Optimisation of four-and five-layer Alx Ga1−x As/GaAs large optical cavity lasers for high power, low threshold current density operation