Semi-insulating Current Blocking Layers Research Articles

Increased modulation bandwidth up to 20 GHz of a detuned-loaded DBR laser

A small signal amplitude modulation bandwidth of 20 GHz has been obtained with a three-section tunable DBR laser fabricated with semi-insulating current blocking layers grown by hydride VPE. The modulation bandwidth and laser linewidth are strongly dependent on the position of the lasing mode relative to the Bragg reflection peak. >

High speed 1.3 mu m InGaAsP Fabry-Perot lasers for digital and analog applications

The digital and analog lightwave transmission characteristics of p-doped active layer 1.3- mu m InGaAsP Fabry-Perot (FP) lasers with semi-insulating current blocking layers were investigated experimentally. For a 1.2-Gb/s digital lightwave transmission system, it was found that the pulse jitter and the resulting power penalty were strongly dependent on the carrier lifetime of the lasers. This indicates that p-doped active layer FP lasers with decreased carrier lifetimes may be usable for a wider range of gigabit lightwave applications than previously considered. For analog lightwave applications, p-doped active layer FP lasers showed a 3-dB modulation bandwidth of 22 GHz for CW operation. These results suggest that this structure is suitable for use in both multigigabit digital and very-high-speed analog lightwave transmission systems. >

Monolithic integration of InGaAsp/Inp lasers and heterostructure bipolar transistors by selective area epitaxy

The authors describe the use of selective area epitaxy to prepare monolithically integrated lasers and heterostructure bipolar transistors based on InGaAsP/InP. Selective growth offers a versatile method of lateral integration of structurally dissimilar devices with the different device structures grown side by side in different growth cycles. Individual devices can be optimised separately without any performance compromise. Bipolar transistors grown on the semi-insulating current blocking layers of the buried heterostructure lasers show high gain, high breakdown voltage and excellent high current stability. Laser threshold is reached at a base current as low as 160 mu A and the light output is linear with current to 10 mW. >

Sub-mA threshold operation of λ=1.5 μm strained InGaAs multiple quantum well lasers grown on (311)B InP substrates

1.5 μm wavelength InxGa1−xAs-InGaAsP (x=0.7, resulting in 1.2% compressive strain and x=0.53, resulting in zero strain) multiple quantum well (MQW) structures were grown on (311)B, (511)A, (511)B, and (001)InP substrates by low-pressure organometallic vapor phase epitaxy (LP-OMVPE). Intense and narrow linewidth room-temperature photoluminescence spectra indicate the device quality of the MQW structures. Strained MQW lasers grown on InP substrates misoriented towards (111)B show about 25% lower threshold current densities than the unstrained MQW lasers. The high quality of the strained MQW structures grown on (311)B InP substrates is demonstrated by the realization of 0.9 mA threshold current buried heterostructure lasers employing semi-insulating current blocking layers, and entirely grown by LP-OMVPE.

Low threshold 1.5 μm tensile-strained single quantum well lasers

We have experimentally found that the threshold current density of 1.5 μm tensile-strained single quantum well lasers decreases with increased tensile strain. A threshold current density as low as of 197 A/cm2 is obtained with an In0.3Ga0.7As well. With semi-insulating current blocking layers and high reflection facet coatings, a threshold current as low as 2 mA is obtained from 150 μm long lasers and a maximum CW operation temperature of 135°C is achieved from 1 mm long lasers.

10 Gbit/s MQW-DFB-SIBH lasers entirely grown by LPMOVPE

The successful realisation of MQW DFB-SIBH lasers for 10Gbit/s systems applications is reported. The SIBH laser structure is completely based on an LPMOVPE growth process, including selective LPMOVPE of semi-insulating current blocking layers. Threshold currents as low as 7 mA and total chip capacitances of 2.6 pF are measured resulting in 6dBel (dBel = electrical dB) corner frequencies in excess of 11 GHz and rise/fall times of 36/44 ps, respectively. A significant reduction of the linewidth broadening compared to bulk lasers is observed which is attributed to a reduced α factor due to quantum wells. A chirp at – 20 dB of 0.47 nm under 10Gbit/s modulation is obtained.

Extremely low threshold current operation in 1.5- mu m MQW-DFB laser diodes with semi-insulating InP current blocking region

Threshold current operation of 1.5 mA was achieved for 1.5- mu m 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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Wide-band modulation of 1.3 mu m InGaAsP buried crescent lasers with iron- and cobalt-doped semi-insulating current blocking layers

The performance characteristics of 1.3- mu m InGaAsP semi-insulating buried-crescent (SIBC) lasers with Fe- and co-doped InP current blocking layers are compared. Threshold currents as low as 10 mA (Fe) and 8 mA (Co) at room temperature, total differential quantum efficiency of 60%, high-temperature operation up to 100 degrees C, high-power output of 42 mW/facet (Fe) and 30 mW/facet (Co), and 3-dB modulation bandwidth of 11 GHz have been achieved. These results indicate that both Fe and Co-doped InP layers grown by low-pressure metalorganic chemical-vapor deposition (LPMOCVD) provide effective current confinement for high-performance semi-insulating buried-crescent lasers (SIBC) lasers. A detailed model based on experimental data for SIBC lasers is also presented for the analysis of intrinsic and parasitic effects on the frequency response of the lasers. The model is then used to design lasers with larger modulation bandwidth. >

1.3 μm InGaAsP buried crescent lasers with cobalt-doped semi-insulating current blocking layers grown by metalorganic chemical vapor deposition

Cobalt-doped semi-insulating InP layers grown by low-pressure metalorganic chemical vapor deposition (LPMOCVD) have been used for the first time as a current blocking layer for 1.3 μm InGaAsP buried crescent lasers. Lasers with this cobalt-doped InP blocking layer have cw threshold currents as low as 8 mA at room temperature. This is the lowest cw threshold current yet reported for an InGaAsP laser with a semi-insulating current blocking layer. In addition, the lasers exhibit total differential quantum efficiency of 60%, high-temperature operation up to 100 °C, high output power of 30 mW/facet, and a 3-dB modulation bandwidth of 11.6 GHz. These results indicate that the cobalt-doped semi-insulating InP layer grown by LPMOCVD provides effective current blocking for high-performance lasers.

Dynamic characteristics of semi-insulating current blocking layers: Application to modulation performance of 1.3-μm InGaAsP lasers

The dependence of current-voltage (I-V) characteristics on Fe-doped semi-insulating (SI) InP layer thickness has been investigated experimentally. The I-V characteristics exhibit nonlinear behavior with ohmic, transition, and space-charge-limited regimes. An approximate circuit model of the buried crescent laser which describes the dynamic characteristics of the SI current blocking layers is presented. It is shown that for a 5-μm-thick SI layer, a very high resistivity of 4.9×108 Ω cm and a very low capacitance of 1 pF are obtained at the typical operating voltage for laser diodes of 1–2 V. Thus, semiconductor lasers with Fe-doped SI InP current blocking layers offer great promise for achieving both wide modulation bandwidth and high-power operation.

High-speed and high-power 1.3-μm InGaAsP buried crescent injection lasers with semi-insulating current blocking layers

The fabrication and performance of high-speed and high-power 1.3-μm InGaAsP buried crescent lasers with semi-insulating current blocking layers are reported. A modulation bandwidth of 11 GHz and acw output power of 42 mW/facet have been achieved. An approximate circuit model of the semi-insulating buried crescent laser, which describes the effect of dc bias on parasitic capacitance at high-speed operation, is also presented.

InGaAsP/InP planar buried heterostructure lasers with semi-insulating InP current blocking layers grown by MOCVD

InGaAsP/InP planar buried heterostructure (BH) lasers with semi-insulating current blocking layers have been realized using LPE and MOCVD hybrid growth. The planar structure has been obtained by developing the selective embedding growth in MOCVD. Low threshold current of 17 mA and high efficiency of 42 percent have been attained with the BH lasers. Small-signal modulation bandwidth of 10 GHz has also been achieved.