Buried Heterostructure Laser Diodes Research Articles

All-selective MOVPE-grown 1.3-μm strained multi-quantum-well buried-heterostructure laser diodes

Strained InGaAsP multi-quantum-well (MQW) double-channel planar-buried-hetero (DC-PBH) laser diodes (LDs) were fabricated by selective metalorganic-vapor-phase epitaxy (MOVPE). In the laser fabrication process, both the strained MQW active layer and current blocking structure were directly formed by selective MOVPE without any semiconductor etching process. The LDs are called all-selective MOVPE-grown BH LDs. The laser fabrication process can achieve both a precisely controlled gain waveguide structure and an excellent current blocking configuration, realizing the optimized DC-PBH structure. These aspects are essential to the high-performance and low-cost LD, which is strongly demanded for optical access network systems or fiber-to-the-home networks. This paper will show the excellent high-temperature characteristics for 1.3-/spl mu/m Fabry-Perot LDs which have a record threshold current of 18 mA with a low-operation current of 56 mA for 10 mW, and 74 mA for 15 mW at 100/spl deg/C with extremely high uniformity. Furthermore, reliable long-term operation at high temperature (85/spl deg/C) and high-output power of 15 mW has been demonstrated for the first time.

Pulse-mode Selective Metal-organic Vapor Phase Epitaxy Method for Migration Enhancement and High-quality Strained InGaAsP Multi-quantum Well Structure

A pulse-mode selective metal-organic vapor phase epitaxy (MOVPE) method for achieving excellent crystal quality of an InGaAsP strained multi-quantum well (MQW) structure on a narrow stripe region was investigated. The migration enhancement mechanism for pulse-mode epitaxy was studied from the view point of the decomposition state of group-III sources. By using the proposed method, the flatness of the selectively grown layers was drastically improved, and a very narrow photoluminescence spectrum linewidth of 28 meV at 25°C was realized for the strained MQW structure. The 1.3 µm-wavelength buried heterostructure (BH) laser diode (LD) with a strained MQW active layer grown by the pulse-mode selective MOVPE showed a very low-threshold current of 12 mA (18 mA) and high-slope efficiency of 0.37 (0.33) W/A at the high temperature of 85°C (100°C).

Sample Preparation of InGaAsP/InP‐Based Lasers for Plan‐View Transmission Electron Microscopy Using Selective Chemical Thinning

A sample preparation method for transmission electron microscopy plan‐views of InGaAsP/InP‐based laser diodes based on selective chemical thinning is described. Using this method, it is possible to prepare samples with more than 50% of the active InGaAsP stripe electron transparent. The method is also comparably fast, simple, reliable, and will not introduce crystal defects in the sample. Examples of the use of this method for preparation of buried heterostructure laser diodes of bulk Fabry‐Perot type are demonstrated. The technique is also applicable to other types of laser diodes, such as multiquantum wells and distributed‐feedback. © 1999 The Electrochemical Society. All rights reserved.

Improved High-Temperature and High-Power Characteristics of 1.3-µm Spot-Size Converter Integrated All-Selective Metalorganic Vapor Phase Epitaxy Grown Planar Buried Heterostructure Laser Diodes by Newly Introduced Multiple-Stripe Recombination Layers

Multiple-stripe planar buried heterostructure (MS-PBH) was newly developed to improve the high-temperature and high-power characteristics of spot-size converter integrated all-selective metalorganic vapor phase epitaxy (MOVPE) grown planar buried heterostructure laser diodes (SSC-ASM-PBH LDs). Recombination-layer stripes were simultaneously grown with the active layer and thickness-tapered waveguide by narrow-stripe selective MOVPE, and inserted in the current-blocking layers. The effect of recombination-layer-stripe insertion was investigated both theoretically and experimentally. The leakage current suppressed by the inserted recombination-layer stripes resulted in improved high-temperature and high-power characteristics. A maximum output power of 47 mW at 85°C, a high characteristics temperature T0 value of 69 K (25°C–85°C), and a small slope-efficiency degradation of 1.1 dB (25°C–85°C) were obtained while maintaining excellent coupling characteristics to a flat-ended single-mode fiber due to its narrow beam divergence.

Tunable twin guide laser diodes with high output efficiency fabricated by an improved reactive ion etching technique

An buried heterostructure (BH) tunable twin guide (TTG) laser diode with low threshold current, high output efficiency (over 0.25 W ) and a tuning range around 2.5 nm has been developed. Since BH laser diodes are highly sensitive to the waveguide quality we have improved the dry etching technique for the definition of the ridge in order to enhance the laser performance. Within the developed reactive ion etching (RIE) procedure a plasma with optimized composition has been used alternating with short plasma steps to remove remaining hydrocarbon polymer contamination deposited during the cycles. The first TTG laser diodes fabricated with this process exhibit up to 30% improved output efficiencies as compared to former devices, and show almost no degradation effects during high temperature lifetime stress.

Threshold currents of 1.3-μm bulk, 1.55-μm bulk, and 1.55-μm MQW DFB P-substrate partially inverted buried heterostructure laser diodes

We investigate the threshold currents of 1.3-/spl mu/m bulk, 1.55-/spl mu/m bulk, and 1.55-/spl mu/m multi-quantum-well (MQW) distributed feedback (DFB) P-substrate partially inverted buried heterostructure (BH) laser diodes experimentally and theoretically. In spite of the larger internal loss of the 1.55-/spl mu/m bulk laser diodes, the threshold current of the 1.55-/spl mu/m bulk DFB P-substrate partially inverted BH laser diode is almost the same as that of the 1.3-/spl mu/m bulk DFB P-substrate partially inverted BH laser diode. The experimentally obtained average threshold current of the 1.3-/spl mu/m bulk DFB P-substrate partially inverted BH laser diodes is 17 mA and that of the 1.55 /spl mu/m bulk DFB P-substrate partially inverted BH laser diodes is 16 mA. The calculated threshold current of the 1.3-/spl mu/m bulk DFB laser diode is 15.3 mA and that of the 1.55-/spl mu/m bulk DFB laser diode is 18.3 mA, which nearly agree with the calculated values, respectively. We have fabricated two types of five-well 1.55-/spl mu/m InGaAs-InGaAsP MQW DFB P-substrate partially inverted BH laser diodes. One has barriers whose bandgap energy corresponds to 1.3 /spl mu/m, and the other has barriers of which bandgap energy corresponds to 1.15 /spl mu/m. The calculated threshold current of the MQW DFB laser diode with the barriers (/spl lambda//sub g/=1.3 /spl mu/m) is 8.5 mA, which nearly agrees with the experimentally obtained value of 10 mA. However, the calculated threshold current of the MQW DFB laser diode with the barriers (/spl lambda//sub g/=1.15 /spl mu/m) is 7.9 mA which greatly disagrees with the experimentally obtained value of 19 mA, which suggests that the valence band discontinuity between the well and the barrier severely prevents the uniform distribution of the injected holes among five wells.

A Hybrid-Integrated Two-Dimensional ( 3×24) High-Efficiency High-Power Laser Diode Array

Using buried-heterostructure laser diodes grown by one-step metal organic chemical vapor deposition and a structure designed to dissipate heat, we have realized a hybrid-integrated two-dimensional high-power laser diode array. The array consists of 3×24 elements, which are individually addressed in a simple matrix. The laser emits at 850 nm and each element operates at 30 mW. The laser characteristics have good uniformity and an energy-conversion efficiency of 45% was achieved. Finite element analysis was used to calculate the thermal characteristics and it was shown that the laser array can be a practical device. The array was operated for more than 1100 h under constant current at room temperature without an external cooler, when the initial power of each laser element was 30 mW, the pulse width was 0.1 ms and the duty cycle was 25%.

Low threshold and high uniformity for novel 1.3-/spl mu/m-strained InGaAsP MQW DC-PBH LDs fabricated by the all-selective MOVPE technique

1.3-μm-strained InGaAsP multiquantum-well (MQW) double-channel planar buried heterostructure laser diodes (DC-PBH-LDs) were fabricated by all-selective metalorganic vapor phase epitaxy (MOVPE). In the fabrication process, the strained MQW active layer and current-blocking structures were directly formed by selective MOVPE without a semiconductor etching process. A low-threshold current (I/sub th/=2.6 mA@25/spl deg/C for 200-μm-long 70%-90% facets) and excellent high-temperature operation (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =84 K, 25/spl deg/C-60/spl deg/C and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =70 K, 25/spl deg/C-85/spl deg/C) were achieved. Furthermore, extremely uniform threshold current and slope efficiency were observed, The median time to failure for these LDs was estimated to be more than 100000 h under the 85/spl deg/C-5 mW aging condition.

Electrical evaluation of InP surface damage by reactive ion etching using mixture of ethane (C 2H 6) and hydrogen (H 2)

The electrical properties of the (100) InP surface were studied based on the fabrication process of a buried heterostructure (BH) laser diode (LD). The current-voltage ( I- V) and capacitance-voltage ( C- V) characteristics were measured for Schottky barriers on the surface at each step of the process. The characteristic variation during the process showed the C 2H 6/H 2-reactive ion etching (RIE) induced damage on the near-surface region: a layer resulting from phosphorus desorption, a low p-concentration layer due to hydrogen passivation, and deep donor defects with electrical drift phenomena. It was found that the damage layers were removed by annealing after the chemical etching which produced almost the same surface as that immediately before the BH regrowth.

Electrical evaluation of InP surface damage caused by reactive ion etching with a mixture of methane (CH4) or ethane (C2H6) and hydrogen (H2)

The electrical properties of a (100) InP surface were studied based on the fabrication process of a buried heterostructure (BH) laser diode (LD). The current–voltage (I–V) and capacitance–voltage (C–V) characteristics were measured for Schottky barriers on the surface at each step of the process—reactive ion etching (RIE) with a mixture of methane (CH4) or ethane (C2H6) and hydrogen (H2), oxygen plasma treatment, chemical etching, and annealing—under conditions which produce almost the same surface as that immediately before the BH regrowth. From the characteristics, it was found that CH4/H2 and C2H6/H2 RIEs caused the appearance of almost the same damage layers as a result of phosphorus desorption and hydrogen passivation in the near-surface region. Furthermore, it was found that only annealing can remove the hydrogen passivation. These results suggest that to obtain a high-quality regrowth interface it is essential to chemically etch the damage layers resulting from phosphorus desorption prior to BH regrowth in the fabrication process of BH-LDs.

High-Performance Strain-Compensated Multiple Quantum Well Planar Buried Heterostructure Laser Diodes with Low Leakage Current

The dependence of leakage current in a planar buried heterostructure laser diode (PBH-LD) on the operating temperature was analyzed by taking the effects of the connection width between a p-InP clad layer and a p-InP blocking layer into account. A two-step etching process comprising nonselective mesa etching followed by InP selective etching is proposed for obtaining a narrow connection width and high controllability of an active layer width. The performance was compared for LDs fabricated using the two-step etching process and those fabricated using conventional nonselective etching process. The average threshold current and the slope efficiency of the 1.3 µ m strain-compensated multiple quamtum well (MQW) PBH-LD fabricated using the two-step etching process were 5.6 mA and 0.27 mW/mA, respectively, for a cavity length of 400 µ m. However, using the nonselective etching process, the average threshold current was 14.5 mA and the slope efficiency was 0.22 mW/mA, given the same cavity length. A higher differential gain and characteristic temperature were also obtained due to the lower leakage currents and strain-compensated multiple quantum well active layers.

Fabrication of Al xGa 1- xAs buried heterostructure laser diodes by in-situ gas etching and selective-area metalorganic vapor phase epitaxy

This paper presents the first successful fabrication of an Al x Ga 1- x As buried heterostructure laser diode (BH-LD) entirely by metalorganic vapor phase epitaxy (MOVPE) without using the wet etching process. The BH-LDs were fabricated by the selective area etching and regrowth (SER) method, combining an in-situ HCl gas etching with a highly selective epitaxy (HSE). These devices operated in a single mode up to 35 mW CW output power. The threshold current was 10.7 mA at 25°C and the difference of the threshold current between 25°C and 60°C was as low as 3.5 mA.

High power InP/InGaAsP buried heterostructure laser for a wavelength of 1.15 μm

InP/InGaAsP buried heterostructure lasers for a wavelength of 1.15 μm with optimized parameters can play an important role as pump sources for blue-upwards conversion fiber lasers. This paper reports the single-step liquid phase epitaxial growth and characterization of a double-channelled substrate InP/InGaAsP buried heterostructure laser diode for a wavelength of 1.15 μm. Optimum conditions for separate growth of an InGaAsP buried active layer on the double-channelled InP substrate have been obtained. Output powers over 100 mW have been obtained by determining the appropriate cavity length and the reflectivity of the mirror facets. High power single-transverse mode operation and a nearly symmetrical beam of the lasers are advantageous for pumping of fiber lasers.

Buried heterostructure AlGaAs photonic devices fabricated by low temperature mesa melt etching and regrowth

Low temperature melt-etching and liquid phase epitaxial regrowth was used to fabricate buried heterostructure laser diode arrays, optical amplifiers and active waveguide branches. 12 element laser diode arrays emitted 1 W total optical power at 1.2 A (room temperature, continuous wave) at 980 nm. 6 dB fiber to fiber optical gain was obtained in buried heterostructure optical amplifiers operating at 830 nm. Active branching waveguides are shown to allow the compensation of 3 db branching losses.

Stress distributions and defect nucleation in buried heterostructure laser diodes

Shear stress distributions, arising at the corners of the active region of buried heterostructure laser diodes, are calculated for a given mismatch and various dimensions of the buried stripe and also for a single and a multiple quantum well structure. The locations of high stresses are compared to the nucleation sites of shear stress induced defects, as observed by transmission electron microscopy in real lasers. The implications of the defects are illustrated and discussed for the case of an overstress tested diode as well as possibilities to prevent the defect formation.

Guided modes and far-field patterns of lead chalcogenide buried heterostructure laser diodes

The far-field of several PbSe/PbEuSe buried heterostructure (BH) laser diodes has been measured. An algorithm for the calculation of the propagation constant and transverse mode function of waveguide structures has been used to calculate the near- and far-field pattern. The theoretical and experimental results are presented and compared with each other. Polarization measurements in the far-field show simultaneous emission of transverse electric (TE) and transverse magnetic (TM) modes from some of the laser diodes.

Peculiarities of catastrophic optical damage in single quantum well InGaAsP/InGaP buried-heterostructure lasers

For investigation of the catastrophic optical damage (COD) of InGaAsP material systems emitting at 0.8 μm, separate-confinement-heterostructure single-quantum-well structures grown on (100) GaAs substrate by liquid-phase epitaxy were mesa-etched for buried heterostructure (BH) laser diodes. The single mode InGaAsP/InGaP diodes were cw operated at room temperature. The measured COD level of a BH InGaAsP/InGaP laser with a cavity length of 470 μm was 8.6±0.7 (MW/cm2). Particularly, we could not observe COD in the long cavity InGaAsP/InGaP lasers, but they showed thermal saturation which is reversible. Also, InGaAsP lasers were found to sustain high current injection three times more strongly than AlGaAs counterparts.

20 GHz Bandwidth High Dynamic Range 1.3 μm Buried Heterostructure Laser Modules

A 20 GHz bandwidth 1.3 μ InGaAsP/InP Straight-Wall Mass-transport Buried Heterostructure laser diode was developed to operate in a microwave fiber optic link. When used in a microwave link, the laser has a typical RF insertion loss of 37 dB, an equivalent input noise density less than -115 dBm/Hz, a 1 dB compression dynamic range greater than 138 dB.Hz and a spurious signal free dynamic range of 97 dB.Hz 2/3 . The wide bandwidth, high dynamic range and low-noise of the laser module were obtained through the design of the package, the subcarrier and the laser chip

Suppression of Side‐Etching in C 2 H 6 / H 2 / O 2 Reactive Ion Etching for the Fabrication of an InGaAsP / InP P‐Substrate Buried‐Heterostructure Laser Diode

A reactive ion etching (RIE) technique using a , , and mixture was applied to the fabrication of (P‐substrate partially inverted buried heterostructure laser diodes, which have been commercially produced for their superior characteristics. The addition of suppressed side etching and made it possible to fabricate ridge mesa structures for the laser diodes with a height of 4 μm and a width of 1 μm with superior controllability. The effects of addition were investigated by Auger electron spectroscopy and a mechanism suppressing side etching was examined. The characteristics including lifetime of the laser diodes fabricated by the RIE technique were as excellent as those of laser diodes fabricated by wet etching.

Self-aligned buried-heterostructure lasers grown entirely by metalorganic vapor phase epitaxy

The effects of n-type dopant on InP embedding regrowth by metalorganic vapor phase epitaxy (MOVPE) are studied. It is found that the growth of the n-InP layer on the mesa structure is completely suppressed under a Se concentration of more than 8×1018 cm−3 and a mesa structure having a width of 1.1 μm. Using this novel MOVPE technique, a buried heterostructure laser diode is successfully fabricated without a selective growth mask. This achieves a threshold current as low as 14 mA, an external differential efficiency of 0.18 W/A, and an output power of more than 15 mW, at 25 °C.