Structure-dependent threshold current density for CdZnSe-basedII-VI semiconductor lasers

The optical gain and threshold current density of CdZnSe-based semiconductor lasers are calculated theoretically with strain and quantum confinement effects taken into account. Both diffusion and drift components are incorporated into the calculation of leakage current. Optimized structures are obtained for CdZnSe-based lasers with different structures through minimizing the threshold current density. A minimum current density of about 200 A/cm² is obtained for a Cd_0.2Zn_0.8Se/ZnS_0.06Se_0.94 /Zn_0.75Mg_0.25S_0.42Se_0.58 modified MQW laser     

Analysis of threshold current density of CdZnSe/ZnSSe strained well lasers

The threshold current density (J/sub th/) of blue-green CdZnSe/ZnSSe strained quantum well lasers is analysed using the laser theory established for III-V semiconductor lasers. Very good agreement between theory and the reported experimental J/sub th/ values is obtained over a wide temperature range from 77 to 273 K. The optimal Cd composition of a CdZnSe single quantum well active layer for obtaining a low J/sub th/ value at room temperature is in the range 0.25-0.30.<>     

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.     

Analysis of threshold current density and optical gain in InGaAsP quantum well lasers

Single-mode and multimode quantum well (QW) laser diodes with emission wavelengths λ=1.0 and 1.58 μm, based on MOCVD-grown separate-confinement heterostructures, have been studied. An analysis of the threshold current density and optical gain is made on the basis of experimental dependences of the threshold current and differential quantum efficiency on the cavity length. The threshold current is decomposed into principal components in terms of model approximations taking into account the Auger recombination, ejection of electrons from QWs into waveguide layers, and lateral current spreading to passive regions of a mesa-stripe laser. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 36, No. 3, 2002, pp. 364–374. Original Russian Text Copyright ? 2002 by Pikhtin, Sliptchenko, Sokolova, Tarasov.     

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.     

Influence of growth conditions on the threshold current density of double-heterostructure lasers prepared by molecular-beam epitaxy

The effect on threshold current density Jth of the use of an air-lock sample-exchange mechanism, substrate preparation and Al source purity was investigated for GaAs-Al0.27 Ga0.73 As double-heterostructure lasers grown by molecular-beam epitaxy (m.b.e.). The conditions necessary to prepare m.b.e. wafers that give Jth as low as for wafers prepared by liquid-phase epitaxy (Jth ? 1 × 103 A/cm2 for an active layer thickness of 0.1 ?m) are summarised.     

Temperature dependence of the threshold current of QW lasers

The temperature dependence of the threshold current in GaInAs-based laser structures has been studied in a wide temperature range (4.2 ≤ T ≤ 290 K). It is shown that this dependence is monotonic in the entire temperature interval studied. Theoretical expressions for the threshold carrier density are derived and it is demonstrated that this density depends on temperature linearly. It is shown that the main contribution to the threshold current comes from monomolecular (Shockley-Read) recombination at low temperatures. At T > 77 K, the threshold current is determined by radiative recombination. At higher temperatures, close to room temperature, Auger recombination also makes a contribution. The threshold current grows with temperature linearly in the case of radiative recombination and in accordance with T ³ in the case of Auger recombination.     

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     

半导体激光器阈值电流的精确测量

一、引言阈值电流是半导体激光器的重要参数之一。通常用测量半导体激光器的输出光功率——电流(PI)特性曲线、观察远场或近场图样的变化以及光谱随电流的变化等来确定阈值,但误差较大。本文用测量半导体激光器调制光信号的二次谐波来确定阈值电流。理论和实验都表明用谐波测量法测定半     

Influence of doping on threshold current of semiconductor lasers

Doping of the active layer of a semiconductor laser reduces the threshold carrier density, the more so the higher the doping level. As a consequence, the threshold current goes through a minimum dependent on doping. This minimum arises for doping densities of the order of 1018 cm?3, and lies about 25% below the value without doping for an n-doped InGaAsP laser. As the temperature dependence of the threshold current is simultaneously weaker (T0?85°), appropriate n-doping may improve the efficiency of a semiconductor laser. Additionally, it is shown that n-doping is more favourable than p-doping.     

两段式双稳半导体激光器下跳阈值点的确定

对Ｋｕｚｎｅｔｓｏｖ采用的速率方程加以修正，考虑了俄歇效应的影响，我们流子寿命不再作为常数处理，而写成载流子浓度的函数。由此导出了两段式双稳半导体激光器下跳阈值点载流子浓度所满足的隐函数解析表达式。通过该解析表达式确定出了器件存在双稳的必要条件。进而讨论了俄歇复合系数、吸收区偏置电流和长度等对双稳特性的影响。     

Above-threshold analysis of loss-coupled DFB lasers: threshold current and power efficiency

The threshold current and power efficiency of loss-coupled DFB lasers have been calculated numerically using an above-threshold model. Compared with perfectly AR-coated devices, lasers with asymmetric facet coatings have substantially lower threshold current. However, significantly higher front-facet power efficiency is only possible at small grating-coupling coefficients. In particular, the range of loss-coupling coefficients for higher efficiency becomes narrower with larger grating duty cycle and larger index-coupling coefficient. These results can be explained by the interdependence of the reflectivity and extra loss associated with loss-coupled gratings.     

Low threshold current density operation of GaInP-AlGaInP visiblemultiple quantum wire-like lasers (MQWR-LDs) under the room temperaturepulsed 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/cm² was obtained. Anisotropic lasing characteristics between [011] and [011¯] directions, in threshold current density, lasing mode, and lasing wavelength were observed     

Temperature dependence of threshold current of GaAs quantum well lasers

The radiative recombination rate in a quantum well structure is calculated using a constant density of states and the k-selection rule. This calculation shows that the threshold current of a GaAs quantum well laser has low temperature sensitivity (T0 ? 330 K for T > 300 K).     

Room temperature operation of microdisc lasers with submilliamp threshold current

Electrically pumped whispering-gallery mode microdisc lasers with singlemode operation and submilliamp threshold current at room temperature are demonstrated. The device consists of an InGaAs/InGaAsP multiple quantum well (MQW) structure formed into a 2-10 mu m diameter disc approximately 0.1 mu m thick. These microdiscs are supported on an InP pedestal.<>     

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     

Very low threshold current ridge-waveguide AlGaAs/GaAs single-quantum-well lasers

Ridged-waveguide AlGaAs/GaAs single-quantum-well lasers were fabricated from a molecular-beam-grown GRIN-SCH wafer in which a superlattice buffer layer was introduced. Fabricated diodes exhibited excellent lasing characteristics including a very low threshold current of 5 mA with a T0 value as high as 160 K.     

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％。