GaAs-GaAlAs heterostructure lasers on semi-insulating substrates

Two structures of GaAs-GaAlAs heterostructures were fabricated on semi-insulating substrates. Low-threshold single-mode operation was achieved. The integration of a laser with an active electronic device (Gunn oscillator) on the same chip of GaAs was demonstrated.     

1.5 ?m region InP/GaInAsP buried heterostructure lasers on semi-insulating substrates

InP/GaInAsP buried heterostructure (BH) lasers for the 1.5 ?m region have been fabricated on semi-insulating InP substrates. The threshold current of the lasers is as low as 38 mA under CW operation at 25°C, which is nearly the same as for BH lasers fabricated on n-type InP substrates.     

Buried heterostructure AlGaAs lasers on semi-insulating substrates

Buried heterostructure (BH) AlGaAs lasers were fabricated on Cr-doped semi-insulating substrates. Low threshold current (8 mA/?m stripe width for cavity length of 300 ?m), a high differential quantum efficiency (55%), and stable transverse mode operation were realised.     

Low threshold current densities for II-VI lasers

II-VI-semiconductor-based, green-light-emitting laser diodes with significantly improved characteristics are reported. Threshold current densities of 42 A/cm² are obtained. Novel contacts also lead to a 25% reduction in the threshold voltage and to an increased device lifetime by a factor of 24 as compared to previous results     

The properties of MOVPE grown 1.3 μm DFB MQW lasers infilled with semi-insulating InP fabricated on semi-insulating substrates

The use of optoelectronic integrated circuits (OEICs) is now emerging as a practical technology for a variety of applications, particularly in advanced telecommunications. OEICs consist of a range of devices such as lasers, waveguides, modulators, amplifiers, transistors, detectors, etc. fabricated on the same substrate. When a semi-insulating substrate is used, these devices can be electrically isolated by channel etching, resulting in a low capacitance structure with reduced electrical interference between the subcomponents. One of the devices which is particularly advantageous for this type of integration scheme is the distributed feedback (DFB) laser. The laser can be made to function more efficiently by minimizing the current flowing outside the active region. This can be achieved by surrounding the active region with semi-insulating iron doped InP. This work describes for the first time, the MOVPE growth, fabrication, and device characterization of 1.3 um buried heterostructure DFB MQW lasers, which combine the advantages of using both a semi-insulating substrate and a semi-insulating infill region in the same device structure. The potential advantage of this design scheme is improved OEIC performance as a result of, reduced capacitance and electrical crosstalk, enhanced laser output power, higher speed, increased efficiency, wider operating temperature and reduced threshold current. The laser active region consists of 8 x 140 Å quantum wells of GalnAsP (λ = 1.3 μm) and 110 Åbarriers of GalnAsP (λ= 1.07 μm). Single mode 1.3 urn devices of length 250 μm operating at room temperature produced threshold currents of 8 mA, efficiencies of up to 25%, output powers of 18 mW at 80 mA (pulsed), and a frequency response greater than 12GHz. The parasitic capacitance was estimated to be less than 3 pF.     

Low threshold current 1.5-μm buried heterostructure lasers usingstrained quaternary quantum wells

Buried heterostructure lasers operating at a wavelength of 1.5 μm with four compressively strained quaternary quantum wells (strain ~1.8%, thickness ~90 Å) and current blocking layers were made using atmospheric pressure metalorganic chemical vapor deposition. Pulsed room-temperature threshold currents for uncoated devices as low as 4.1 mA and as low as 0.8 mA for devices with high reflectivity mirror coatings are reported. The dependence of threshold current on active region width is consistent with broad-area laser measurements     

Low threshold 1.5 mu m tensile-strained single quantum well lasers

The authors have experimentally found that the threshold current density of 1.5 mu m tensile-strained single quantum well lasers decreases with increased tensile strain. A threshold current density as low as of 197 A/cm/sup 2/ is obtained with an In/sub 0.3/Ga/sub 0.7/As well. With semi-insulating current blocking layers and high reflection facet coatings, a threshold current as low as 2 mA is obtained from 150 mu m long lasers and a maximum CW operation temperature of 135 degrees C is achieved from 1 mm long lasers.<>     

Low threshold current GaAs/GaAlAs GRIN-SCH stripe lasers grown by OMVPE

The letter describes the characteristics of stripe lasers formed in GaAs/GaAlAs single-quantum-well graded-composition separate-confinement heterostructures (GRIN-SCH) grown by low-pressure organometallic vapour phase epitaxy (LP-OMVPE). We show that the low threshold current density that has been achieved with the GRIN-SCH structure allows low threshold currents (38 mA) to be achieved in a simple gain-guided stripe-geometry laser. These low thresholds have been obtained without resorting to a complex nonplanar (lower yield) technology, and it is shown that the good uniformity offered by OMVPE is maintained through to the mounted device stage.     

Consideration on threshold current density of GaInAsP/InP surface emitting junction lasers

The oscillation condition of the GaInAsP/InP surface emitting (SE) junction laser (lambda = 1.3mum) is examined. Theoretical calculations indicate that reflectivity of the mirrors of a Fabry-Perot resonator is necessary to be 95 percent for a reasonably low threshold current density. Then, we have fabricated a new structure for SE laser and compared its threshold current density with the theoretical estimation. In order to maintain the necessary reflectivity without deteriorating the ohmic contact, we adopted a ring electrode where the reflecting mirror is separated from thep-side electrode. The threshold current was reduced down to 35 mA at 77 K which is 70 percent of the early experiment. The threshold current density was estimated to be 5 kA/ cm². The estimated reflectivity was 80-85 percent. The operating temperature has been raised to -21°C (252 K). The temperature dependence of the threshold current near room temperature suggests that room temperature operation of GaInAsP/InP SE lasers is possible by increasing the reflectivity of mirrors and current confinement.     

低阈值电流、高量子效率脊形波导激光器

研制了低阈值电流、高量子效率670nm压缩应变单量子阱GaInP/AIGalnP脊形波导激光器。测量解理成的激光器条,腔长为300μm时,阈值电流为12．8mA,双面外部量子效率之和达到94．6％。     

Low threshold current high-temperature operation of InGaAs/AlGaAsstrained-quantum-well lasers

The authors report improved high-temperature characteristics for In_0.2Ga_0.8As strained-quantum-well ridge waveguide lasers with an optimized cavity design. They have fabricated In_0.2 Ga_0.8As lasers that operate CW at up to 220°C with over 9-mW output power. At 200°C the threshold current is as low as 15.9 mA for a 400-μm-long laser with 35/98% reflectivity facets. Optimization of the laser cavity also improves the high-temperature operation of quantum-well lasers in other material systems; GaAs quantum well lasers that operate at up to 220°C CW have been fabricated     

Extremely low threshold current operation in 1.5-μm MQW-DFBlaser diodes with semi-insulating InP current blocking region

Threshold current operation of 1.5 mA was achieved for 1.5-μm multiple-quantum-well distributed feedback (MQW-DFB) laser diodes (LDs) with semi-insulating current blocking layers entirely grown by metalorganic vapor phase epitaxy (MOVPE). Such low-threshold current is attained by reducing leakage current and mirror loss in the laser structure. The required bias current for achieving several gigahertz bandwidth is markedly reduced due to the enhanced differential gain and low threshold current. Due to the reduced lasing delay time in such low threshold LDs, up to 5-GHz zero-bias current modulation, with a clear eye opening, is successfully demonstrated     

Low threshold channelled-substrate buried crescent InGaAsP lasers emitting at 1.54 ?m

Double-heterostructure lasers with crescent-shaped InGaAsP active layers have been fabricated with CW emission of 1.54 ?m. Lowest CW thresholds are 45?47 mA for a 200 ?m long cavity at 25°C. The lasing near-field widths are 2.5?3.0 ?m and the spectral widths to 10% of peak are 4?5 nm under both CW conditions and modulation up to 320 Mbit/s.     

Integratable, high speed buried ridge DFB lasers fabricated on semi-insulating substrates

The fabrication of buried ridge DFB lasers on semi-insulating substrates is described. A novel contacting mechanism was employed to give a series resistance of less than 4 Omega . Devices were fabricated at both 1.3 and 1.53 mu m with lasing thresholds as low as 16 mA. Single longitudinal mode operation was achieved with SMSR greater than 30 dB at both wavelengths. The structure gives an inherently low capacitance, which together with low threshold currents, low series resistance and fabrication on SI substrates makes these devices suitable for integration and high speed applications.<>     

n-channel formation on semi-insulating InP surface by m.i.s.f.e.t.

InP m.i.s.f.e.t.s using Fe-doped semi-insulating material surface have been fabricated. The devices, composed of sulphur-diffused n-type source and drain and c.v.d. Al2O3 gate insulator, exhibited n-channel normally-off behaviour and a source drain capacitance two orders of magnitude smaller than that of p-InP m.i.s.f.e.t.s with the same dimensions.     

Low threshold 1.55 ?m InGaAsP lasers double clad with InGaAsP confining layers

Preliminary results for 1.55 ?m InGaAsP double-heterostructure lasers with symmetrical InGaAsP confining layers are presented. The lowest broad-area threshold is 1.36 kA/cm2, which is 30% lower than the best value previously reported for 1.55 ?m lasers. This improvement is believed to be related to the absence of terracing on InGaAsP confining layers.     

Reduction of threshold current density of 2.2?m GaInAsSb/AlGaAsSb injection lasers

GaInAsSb/AlGaAsSb injection lasers have been fabricated with increased Al concentration in the cladding layers. As a result of improved optical and electrical confinement, the threshold current density Jth for these double heterostructures was a factor of two lower than reported previously; CW operation was achieved up to 235 K.     

Pressure dependence of threshold current and carrier lifetime in 1.55 ?m GaInAsP lasers

The threshold current and carrier lifetime were measured as a function of pressure in oxide stripe and IRW GaxIn1?xAsyP1?y 1.55 ?m lasers. The results indicate that intervalence band absorption is a more important loss mechanism than the combined effects of Auger recombination, loss over the barrier and recombination through defects.     

Low threshold current AlGaAs/GaAs rib-waveguide separate-confinement-heterostructure distributed-feedback lasers grown by metalorganic chemical vapor deposition

AlGaAs/GaAs rib-waveguide separate-confinement-heterostructure (SCH) distributed-feedback (DFB) lasers emitting at 880 nm were fabricated by a two-step atmospheric pressure metalorganic chemical vapor deposition (MOCVD) growth technique. A CW threshold current as low as 18 mA and an output power of more than 10 mW per facet at room temperature were obtained. Also, single longitudinal and fundamental transverse modes were maintained up to more than twice the threshold current level.