Buried Heterostructure Laser Diodes Research Articles

1.3-μm InGaAsP planar buried heterostructure laser diodes with AlInAs electron stopper layer

This study reports on the realization of 1.3-μm InGaAsP buried-heterostructure (BH) laser diodes (LDs) via an Fe-doped semi-insulating InP layer and an AlInAs electron stopper layer (ESL). Experimentally, the as-cleaved BH LD with an AlInAs ESL exhibited improved characteristics in terms of threshold current, slope efficiency, and maximum light output power at 90 °C as compared to those of the normal BH LD without an AlInAs ESL. In addition, high internal quantum efficiency or reduced threshold current density was observed, indicating increased modal gain in BH LDs fabricated with an AlInAs epilayer on top of the active region. It was also found that the temperature sensitivity of the BH LDs with an AlInAs ESL is more stable than that of the normal BH LDs. These results could be attributed to the suppression of thermal carrier leakage out of strain-compensated multiple-quantum-well by a large conduction-band offset of the AlInAs/InGaAsP heterojunction. Otherwise, without consideration of damping factor or coupling loss, the 3-dB bandwidth of the proposed BH LDs reaches a high value of 15.3 GHz. Finally, this TO-can packaged BH LD shows an eye-opening feature with the extinction ratio of 7.49 dB while operating at 10 Gbit/s at 50 mA.

1.3 μm Strain-Compensated InGaAsP Planar Buried Heterostructure Laser Diodes with a TO-Can Package for Optical Fiber Communications

In this paper, we report on the realization of the 1.3 μm strain-compensated InGaAsP buried heterostructure (BH) laser diodes (LDs) by using an Fe-doped semi-insulating InP layer. The performances of LDs are characterized by light output power, internal quantum efficiency, modal gain, characteristic temperature , and dynamic response. As a result of the good confinement of the injection carriers within the strained-compensated multiple quantum well (SC-MQW) and the better heat sink for thermal dissipation, the BH LDs exhibit a threshold current of 9 mA, a slope efficiency of 0.296 mW/mA, and a maximum light output power of 11.8 mW/facet at 76 mA. Besides, the transparent current density and modal gain are estimated as and , respectively, for the fabricated LDs. Otherwise, the BH LD with a facet coating is beneficial to get a lower threshold current, a higher light output power, and an improved value as compared to the conventional ridge-waveguide LD. Furthermore, this transistor outlook (TO)-packaged BH LD for small-signal analyses does not show any parasitic effects at low frequencies and has a maximum modulation frequency of 9.6 GHz at 80 mA. Finally, the BH LD also exhibits the promising potential for high speed data transmission as evaluated from the 10 Gb/s eye-opening feature. These results imply that the 1.3 μm TO-packaged SC-MQW InGaAsP LDs are excellent candidates for use in high speed optical fiber communications.

Failure Analysis of InP-Based Edge-Emitting Buried Heterostructure Laser Diodes Degraded by Forward-Biased Electrostatic Discharge Tests

We investigated the forward-biased electrostatic discharge (ESD)-induced degradation that is one of the important reliability issues for InP-based edge-emitting buried heterostructure laser diodes. Although it has been suggested that the degradation mechanism is related to optical damage, the detailed mechanism has not been established. Thus, we carried out failure analysis. Two elliptically shaped degraded regions, which were introduced by the first and second ESD pulses, were observed in an active layer. A peculiar chain-like degradation was created along the longitudinal axis. This degradation was caused by light absorption at an active layer. We also investigated the relationship between forward-biased ESD tolerance and an aging test. We observed a decrease in tolerance as a result of the aging test for laser diodes with cleaved facets. This decrease was sufficiently suppressed by facet coating. We identified two reasons why facet coating is important. One is to obtain sufficient ESD tolerance under initial conditions, and the other is to suppress the decrease in ESD tolerance during aging.

Relationship between Reverse-Biased Electrostatic-Discharge Tolerance and Aging of GaInAsP/InP Buried-Heterostructure Laser Diodes

Degradation due to electrostatic discharge (ESD) is an important reliability issue for GaInAsP/InP buried-heterostructure laser diodes (LDs). Although this degradation mechanism has been previously discussed, the relationship between ESD tolerance and aging has not been investigated. For forward-biased ESD, the degradation mechanism is similar to that of catastrophic optical damage. Therefore, ESD tolerance can be assumed to decrease during an aging test. However, the relationship between reverse-biased ESD tolerance and aging is less clear. We investigated this relationship, focusing particularly on reverse bias, and observed a decrease in ESD tolerance owing to aging. Specifically, the ESD tolerances decreased by approximately 30 and 70% for facet-coated and uncoated GaInAsP/InP Fabry–Perot LDs, respectively, as a result of aging longer than 3000 h. We determined that facet coating is effective in suppressing the reduction in ESD tolerance caused by aging.

In Ga As P ∕ In P buried-heterostructure laser diodes grown on InP using molecular beam epitaxy and metal-organic chemical vapor deposition

Buried-heterostructure (BH) laser diodes were fabricated using both molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). MBE was used to grow the active region and the p-type cladding and contact structures while MOCVD was used for the Fe-doped, blocking layer structures. Using this method, devices were fabricated which showed good performance over the temperature range of −20–85°C. Devices were demonstrated at several wavelengths including 1550 and 1610nm. Room temperature operation of the unpackaged 1610nm devices, with coated facets, demonstrated threshold currents as low as 6mA and efficiencies of 0.3mW∕mA. The same devices operating at 85°C showed threshold currents as low as 22mA and efficiencies of 0.2mW∕mA. Coaxial, fiber pigtailed devices consistently demonstrated OC-48 dispersion power penalties of less than 1.5dB for fiber spans of 100km. Preliminary device reliability shows minimal degradation. TO-56 packaged devices operating at a constant power of 6mW at 90°C for over 4000h have shown a maximum of 3% increase in operating current. The performance and excellent reliability of these devices indicate that this method can be used for the low-cost manufacture of BH distributed feedback lasers.

Nonuniform output characteristics of laser diode with wet-etched spot-size converter

We study the output characteristics of spot-size converter (SSC) integrated buried heterostructure (BH) laser diode (LD) by forming SSC with wet etching process. SSC-LD shows large chip-to-chip variation in threshold current(Ith) and slope efficiency (eta(slope)) compared to LD without SSC. Ith and eta(slope) are closely related with each other so that the front facet eta(slope) increases while the rear facet eta(slope) decreases with Ith. Far-field angle is also found to be proportional to the front facet eta(slope). The trends observed are explained clearly by a unidirectional loss occurring when photons travel from the front to rear facet.

High-Reliable and High-Speed 1.3 $\mu$m Complex-Coupled Distributed Feedback Buried-Heterostructure Laser Diodes With Fe-Doped InGaAsP/InP Hybrid Grating Layers Grown by MOCVD

In this paper, we report the fabrication of high-reliability and high-speed 1.3 mum complex-coupled distributed feedback (CC-DFB) buried heterostructure (BH) laser diodes (LDs) with Fe-doped InGaAsP/InP hybrid grating layers. High optical coupling coefficient and eminent current confining ability are accomplished by combining the Fe-doped InGaAsP/InP current-blocking-grating (CBG) layers to provide both the distributed-feedback index-and gain-coupling coefficients. Besides, the narrow-stripe BH LDs are implemented by burying the active region with a Fe-doped InP current-blocking layer during the epitaxial regrowth. The fabricated CBG CC-DFB BH LDs at 20degC shows a low threshold current of 5.3 mA, a maximum light output power of 36 mW at 100 mA, a high slope efficiency of 0.41 mW/mA, and a side-mode suppression ratio (SMSR) of 42 dB at twice the threshold. In addition, these LDs exhibit a maximum operation temperature of 125degC, an extremely low threshold current of 15.8 mA at 90degC, a small variation in slope efficient of only -1 dB in the temperature range from 20degC to 80degC, and a characteristic temperature of 77 K and 56 K between 20 degC and 60degC, and 70degC and 120degC, respectively. Furthermore, these 1.3 mum CBG CC-DFB BH LDs exhibit a high-speed characteristic up to 11.8 GHz at room temperature and an estimated median lifetime of more than 1.1 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> h or 12.5 years at 5 mW and 85degC.

High Performance 1.55 μm InGaAsP Buried-Heterostructure Laser Diodes Fabricated by Single-Step MOCVD Regrowth and Self-Aligned Technique

In this article, we demonstrate a simple and low-cost method to fabricate the strained multiquantum-well buried-heterostructure (BH) laser diodes (LDs) by using the single-step metallorganic-chemical-vapor-deposition (MOCVD) regrowth and self-aligned technique. The active region is buried by the intrinsic layer which is used as the current-blocking layer as well as the electrical and optical confinement layer. The BH LDs have a calculated internal quantum efficiency of 81% and an internal loss of . The fabricated as-cleaved BH LDs exhibit a threshold current of , a maximum light output power of at , a maximum operating temperature of , and a characteristic temperature of in . The BH LDs with an as-cleaved front facet and a high reflectivity coating applied to the rear facet can increase the maximum operation temperature up to and have a light output power exceeding at and . The frequency at a bias current of is 8.0, 6.5, and at 30, 60, and , respectively. Besides, the modulation bandwidth can be extended as far as at and . These results confirm that BH LDs have the potential capacity for high-speed fiber optic applications.

High-speed and uncooled operation of 1.3-/spl mu/m InGaAsP strain-compensated MQW BH lasers fabricated on patterned InP substrates

The fabrication and characteristics of 1.3-/spl mu/m InGaAsP strain-compensated multiquantum well (SCMQW) buried heterostructure (BH) laser diodes (LDs) grown by selective metal-organic chemical vapor epitaxy on a patterned InP substrate are demonstrated. The photoluminescence (PL) of the SCMQW active region grown on the patterned grooves has a narrow full-width at half-maximum of /spl sim/ 47 meV. The BH LDs exhibit a threshold current of 6.8 mA, a slope efficiency of 0.45 mW/mA, and a light output power exceeding 30 mW at 80 mA and 20/spl deg/C. The maximum operating temperature is 120/spl deg/C with a characteristic temperature of 72 K in 20/spl deg/C-80/spl deg/C. The 3-dB modulation bandwidth can be extended as far as 11.4 GHz under a bias level of 40 mA, and the back-to-back tests show a clear and symmetric eye diagram at 10 Gb/s with a PRBS of 2/sup 31/-1 word length and a peak-to-peak voltage of 1.08 V at 85/spl deg/C. The average increase in operational current is smaller than 0.84% after the 1500-h aging test. The mean time of the BH LDs operated at 85/spl deg/C to fail is calculated as 9/spl times/10/sup 4/ h. These BH LDs satisfy the reliability requirement for strict loop environment and 10-Gb Ethernet application without special hermetic packaging.

Experimental Study on the Intrinsic Response, Optical and Electrical Parameters of 1.55-$muhboxm$DFB BH Laser Diodes During Aging Tests

This paper reports on an investigation on the light–current, relative intensity noise, and chirp variations of life-tested InGaAsP/InP multiquantum-well buried heterostructure (BH) laser diodes (LDs). The devices have been stressed at highly accelerated aging conditions ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I = 170 hboxmA$</tex> , <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T = 140 ^circhboxC$</tex> for 3000 h). Typically, the operating current at constant output optical power <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(I_ op)$</tex> increases logarithmically with time in stable devices while the noise resonance frequency remains stable. High-frequency RF signal-induced chirp for relative stable LDs at constant output power shows very little change with time.

Thermally widely tunable laser diodes with distributed feedback

A thermally widely tunable buried heterostructure laser diode with distributed feedback (DFB) is demonstrated. This device requires only two tuning currents for wide quasicontinuous wavelength tuning, thereby facilitating easy and fast device calibration and control. Furthermore, being based on regular DFB laser fabrication technology, it is readily manufacturable. By using window structures instead of cleaved facets plus antireflection coatings, a regular tuning behavior has been achieved for a DFB-like widely tunable laser diode with only two tuning currents. The laser diode covers the wavelength range between 1552 and 1602 nm. Requiring side-mode suppression ratio and output power above 30 dB and 10 mW, respectively, a wavelength range of 43 nm is accessible.

InGaAs/AlGaAs Quantum Wire DFB Buried HeteroStructure Laser Diode by One-Time Selective MOCVD on Ridge Substrate

A quasi-buried heterostructure (BH) quantum wire (QWR)-distributed feedback (DFB) laser was realized by one-time selective metalorganic chemical vapor deposition (MOCVD) on a ridge substrate with a submicron grating. One-time selective MOCVD led to the formation of a ridge waveguide with a BH structure and a QWR array for gain-guided DFB laser diode (LD) without additional etching or regrowth process. The threshold current is 15 mA, and the threshold current density is 850 A/cm2. A stable single longitudinal mode was preserved until 3 Ith, after which another mode emerged at a high drive current at 813.6 nm. This suggests a complex-coupled DFB-mode operation. The elimination of the regrowth step enlarges the range of material for extended wavelengths and operational temperatures.

Optimizing HBr ­ Br2 ­ H 2 O Etchants to Form Low Defect Regrowth Interfaces for Highly Reliable InGaAsP/InP Buried-Heterostructure Lasers

We have obtained a tenfold improvement in the reliability of InGaAsP/InP buried heterostructure laser diodes having a dry-etched mesa structure by optimizing the composition of a etchant to produce smooth mesa sidewalls, thus reducing the number of defects at regrowth interfaces. The optimal etchant, which has a composition in the range from 0.30 M HBr/0.022 M to 0.50 M HBr/0.020 M etches both the InP cladding layers and the InGaAsP multi-quantum-well active layer at the same rate. We propose a simple model of the etching process that is consistent with the observed etching characteristics. We found that the etching rate was controlled by the diffusion of molecules, which act as oxidizing agents. © 2003 The Electrochemical Society. All rights reserved.

Contact potential measurement of cleaved mirror surface of 1.3 µm buried heterostructure laser diode by Kelvin probe force microscopy

Contact potential images of a cleaved mirror surface of a 1.3 /spl mu/m buried heterostructure laser diode by Kelvin probe force microscopy have been successfully obtained. The embedded current blocking layer and mesa-etched active region were clearly recognised.

Optical and Electrical Characteristics of InGaAsP MQW BH DFB Laser Diodes

In this paper we present lasing delay time, optical and electrical low-frequency noise, and correlation factor between optical and electrical fluctuations for multiple-quantum-well gain-coupled buried-heterostructure distributed-feedback laser diodes with thyristor-type blocking layer. The investigated laser diodes had very low threshold current (6-8 mA) and lasing delay time ( 100 mA). The investigated lasers exhibited thyristor-like turn-on at currents >100 mA.

All selective metalorganic vapor phase epitaxy grown buried-heterostructure laser diodes with selectively oxidized AlInAs current-confinement layer

A laser diode structure, consisting of a 1.3 μm all selective metalorganic vapor phase epitaxy grown buried-heterostructure (ASM-BH) laser diode with a selectively oxidized-AlInAs current-confinement layer, is proposed and demonstrated. As the lateral oxidization is automatically stopped near the active layer by self-aligned AlInAs, a narrow current aperture with excellent controllability is realized. The fabricated laser diode shows low continuous-wave threshold current of 2.5 and 7.5 mA at 25 and 85 °C, respectively, for 250-μm-long devices with HR(75%)/HR(95%) coatings. The maximum operating temperature is higher than 145 °C.

Effect of p-doping profile on performance of strained InGaAs/InGaAsP multiple quantum well buried heterostructure laser diodes with Fe- or p/n/p-doped InP current blocking layer

The effect of p-doping profile on performance of InGaAs/InGaAsP strained MQW BH LD with Fe-doped or p/n/p-doped InP current blocking layer was investigated. LDs with a p-doped SCH exhibited a higher slope efficiency compared to those with an undoped SCH regardless of current blocking type. The observed high degree of nonlinearity in the light-output power and low characteristic temperature of the semi-insulating blocking type lasers with a p-doped SCH layer suggest that the interdiffusion of Fe and Zn across the interface between p-doped SCH (and p-InP:Zn) layer and SI-InP:Fe layer has given rise to leakage currents in laser device.

Impact of neutron irradiation on optical performance of InGaAsP laser diodes

Results are presented of an extended study on the degradation and recovery behavior of optical and electrical performance and on induced lattice defects of 1.3 μm InGaAsP double channel planar buried heterostructure laser diodes with an In0.76Ga0.24As0.55P0.45 multi-quantum well active region, subjected to a 1 MeV fast neutron and 1 MeV electron irradiation. The degradation of the device performance increases with increasing fluence. Two hole capture traps with near midgap energy level in the In0.76Ga0.24As0.55P0.45 multi-quantum well active region are observed after a 1×1016 n/cm2 irradiation. These deep levels are thought to be associated with a Ga vacancy. The decrease of optical power is related to the induced lattice defects, leading to a reduction of the non-radiative recombination lifetime and of the carrier mobility due to scattering. The difference in radiation damage between 1 MeV fast neutrons and 1 MeV electrons is discussed taking into account the non-ionizing energy loss (NIEL). The radiation source dependence of performance degradation is attributed to the difference of mass and the probability of nuclear collision for the formation of lattice defects. The decreased optical power recovers by thermal annealing, and the recovery increases with increasing annealing temperature. The optical power recovers by 45% for 1 MeV neutron irradiation with a fluence of 1×1015 n/cm2 after a 300°C annealing.

Radiation-induced lattice defects in InGaAsP laser diodes and their effects on device performance

Results are presented of an extended study on the degradation and recovery behavior of optical and electrical performance and on induced lattice defects of 1.3μm InGaAsP double channel planar buried heterostructure laser diodes with an In0.76Ga0.24As0.55P0.45 multi-quantum well active region, subjected to 1-MeV fast neutron and 1-MeV electron irradiation. The degradation of the device performance increases with increasing fluence. Two hole capture traps with near midgap energy level in the In0.76Ga0.24As0.55P0.45 multi-quantum well active region are observed after 1×1016n/cm2 irradiation. These deep levels are thought to be associated with a Ga-vacancy. The decrease of optical power is related to the induced lattice defects, leading to reduction of the non-radiative recombination lifetime and of the carrier mobility due to scattering.

Thermal cleaning of air-exposed p-type InGaAs films and CBE regrowth of carbon-doped InGaAs layers for optical device applications

We have studied thermal cleaning of air-exposed Zn-doped InGaAs films and regrowth of carbon-doped InGaAs layers in terms of carrier concentration profiles and residual oxides. As the cleaning temperature prior to CBE regrowth is increased, the residual oxides at the regrowth interface exponentially decrease, and the carrier concentration at the interface approaches the intentional doping level. Elevating the temperature to 575°C provides a “clean” interface, i.e., the carrier profiles are flat. SIMS reveals that the carbon atoms doped to 10 20 cm −3 in the CBE film do not diffuse to the adjacent Zn-doped MOCVD film at all. The thermal cleaning and regrowth procedure was applied to an air-exposed MOCVD film with laser structure for the purpose of nonalloy ohmic contact layer. 1.3 μm-wavelength buried-heterostructure laser diodes with cleaved facets have a large light output of more than 20 mW per facet.