Reliable InGaAs quantum well lasers at 1.1 mu m

Strained-layer InGaAs quantum well lasers operating CW at 1.1 mu m have been life tested to over 18000 h, exhibiting a degradation rate of <.8% per kh. These uncoated lasers were life tested at 70 mW (per facet) in constant-power mode at a heatsink temperature of 30 degrees C. The laser structure, grown by metalorganic chemical vapour deposition, incorporates a step-graded quantum well heterostructure with a 30 AA In/sub 0.45/Ga/sub 0.55/As quantum well.<>     

Properties of wide-mesastripe InGaAsP/InP lasers

Wide-mesastripe InGaAsP/InP heterostructure lasers emitting at 1.3–1.5 µm were grown by metal-organic chemical vapor deposition (MOCVD). Radiation-power-current and spectral characteristics of the lasers have been studied in pulsed and continuous wave (cw) operation in the temperature range of 10–60°C. The temperature of the active region of the diode laser is higher by 30–60°C than that of the copper heatsink upon saturation of the cw output power. The temperature dependence of the differential quantum efficiency strongly affects the cw output power. Output powers of 3 and 2.6 W are achieved in mesastripe lasers in cw operation, and 9 and 6.5 W in pulsed operation, at wavelengths of 1.3 and 1.5 µm, respectively.     

Formation of TiN/TiSi2/p+-Si/n-Si by rapid thermal annealing (RTA) silicon implanted with boron through titanium

A low temperature method of fabricating conductive (3.5 Ω/ sq.) p⁺/n junction diodes possessing excellentI-Vcharacteristics with reverse-bias leakage less than -3 nA.cm^-2at -5 V is described. Single crystal n-type 〈100〉 Si is implanted with 60 keV¹¹B+through 0.028-µm thick sputtered Ti film. Rapid thermal annealing (RTA) in an N2ambient simultaneously forms a 0.36-µm deep p⁺/n junction and a 0.063-µm thick bilayer of TiN and TiSi2with a resistivity of 22 µΩ.cm. The electrical properties of these diodes are not degraded by annealing for 30 min at 500°C, suggesting that the outer layer of TiN is an effective diffusion barrier between TiSi2and Al.     

Reliability in InGaAsP/InP buried heterostructure 1.3 µm lasers

A study was conducted of aging-induced Sn whisker growth at the surface of Au-Sn bonding solder layers around a laser chip, as well as metallurgical reactions, especially in p-side down lasers, at the interface of the solder and laser crystal just below the active layer. These phenomena cause electrical shorts in InGaAsP/InP laser diodes, which occur suddenly in devices operated for long periods without any previous symptoms having appeared in their aging characteristics. To completely eliminate such failures, a novel assembling method in which chips were mounted p-side up on semiinsulating SiC submounts using Pb-Sn solder, was applied to InGaAsP/InP buried heterostructure (BH) lasers emitting at 1.3 μm. BH lasers assembled by this method do not suffer any shorting failure even after 8000 h operation under 60°C and 5 mW/facet output conditions. The small degradation rates obtained, for example, 3 percent/kh (median) at 60°C, certify the reliability of these improved lasers. As long as the stripe width of the active layer was optimized to be in the range of1.5-2.5 mum necessary for obtaining kink-free light output versus current properties, no detrimental changes in laser characteristics, including transverse and longitudinal modes and dynamic output response, were observed in aged lasers. In this paper, the long-term degradation modes observed are presented, and possible causes are discussed.     

High-power laser diodes (λ = 808–850 nm) based on asymmetric separate-confinement heterostructures

Symmetric and asymmetric separate-confinement AlGaAs/GaAs heterostructures have been grown by MOCVD in accordance with the concept of design of high-power semiconductor lasers. High-power laser diodes with a 100-μm aperture, emitting in the 808–850-nm range, were fabricated from these structures. The internal optical loss in asymmetric separate-confinement heterostructures with broadened waveguide is reduced to 0.5 cm⁻¹. In the lasers with 1.7-μm-thick waveguide, the output optical power of 7.5 W in CW mode was achieved owing to reduction of the optical emission density at the cavity mirror to 4 mW/cm². Original Russian Text ? A.Yu. Andreev, A.Yu. Leshko, A.V. Lyutetskiĭ, A.A. Marmalyuk, T.A. Nalyot, A.A. Padalitsa, N.A. Ptkhtin, D.R. Sabitov, V.A. Simakov, S.O. Slipchenko, M.A. Khomylev, I.S. Tarasov, 2006, published in Fizika i Tekhnika Poluprovodnikov, 2006, Vol. 40, No. 5, pp. 628–632.     

Highly reliable operation of strain-compensated 0.98 μmInGaAs/lnGaP/GaAs lasers with InGaAsP strained barriers for EDFAs

Highly reliable operation of 0.98 μm strain-compensated InGaAs/ InGaAsP lasers is demonstrated for the first time with an estimated lifetime of 170 kh at 25°C. Moreover, we reveal that the degradation rates at 90°C and 80 mW output power are four times smaller than those of identical lasers with GaAs barriers     

Ten-thousand-hour operation of crank transverse-junction-stripe lasers grown by metal-organic chemical vapor deposition

For over 10 000 h, crank transverse-junction-stripe (TJS) laser diodes, grown by metal-organic chemical vapor deposition (MOCVD) maintain low and quite stable operating currents in the automatic-power-control aging with output power of 5 mW/facet at 55°C and 70°C. These MO-CVD lasers have excellent initial characteristics and small distributions of the characteristics. The reason for this excellent result is discussed in relation to the crystalline quality and the uniform growth of MO-CVD wafers.     

On the reliability of 1.3-µm InGaAsP/InP edge-emitting LED́s for optical-fiber communication

This study of the reliability of 1.3-μm double heterojunction edge-emitting LED's indicates that edge-emitting LED's mounted with Au0.8Sn0.2solder have an activation energy of 0.9 eV for degradation and extrapolated lifetimes of2 times 10^{8}h at room temperature. A study of 1.3-μm LED's grown by LPE and VPE show them to be comparable in operating life. The temperature dependence of the light output (P) of the edge-emitting LED's is given byP alpha exp(-Delta T/75K). The study also showed that lattice mismatch up to 0.31 percent at the InGaAsP/InP heterojunction does not effect reliability.     

Large-area and visible response VPE InGaAs photodiodes

InGaAs photodiodes having diameters of 500 µm have been successfully fabricated by vapor-phase epitaxial techniques. Typical room-temperature performance characteristics at a bias voltage of -10 V are: quantum efficiency ≈80 percent (1 to 1.7 µm); dark current &ap120 nA; noise current &ap0.3 pA/Hz^1/2; capacitance &ap5 pF; and response time &ap3 ns. The useful spectral range of standard 100-µm-diameter diodes has been extended to short Wavelengths (about 0.5 µm) by a reduction in the thickness of the InP capping layer. Quantum efficiencies near 70 percent have been observed at 0.7 µm.     

Normally-off InGaAs junction field-effect transistor with InGaAs buffer layer

InGaAs junction field-effect transistors (JFET's) with 1-µm gate length were successfully fabricated with an n⁺-InGaAs active layer (8 × 10¹⁶cm^-3) and an undoped InGaAs buffer layer grown on semi-insulating InP:Fe substrate by liquid-phase epitaxy. The device showed good pinch-off behavior with a threshold voltage of 0.25 V, a low drain current of 1 µA at zero gate-source voltage, and a very high transconductance of 553 mS/mm at room temperature. This is one of the highest transconductance values ever reported for a 1-µm gate-length FET.     

MOCVD-grown InGaAs/GaAs/AlGaAs laser structures with a broad-area contact

A metal-organic chemical vapor deposition (MOCVD) technique is developed for a diode laser heterostructure in a system of InGaAs/GaAs/AlGaAs solid solutions; the optimal sizes and the doping profile of the structure are determined to minimize the internal optical losses. Mesa-strip diode lasers with a threshold density of current J _th=150–200 A/cm², internal optical loss factor α_i=1.6–1.9 cm^?1, and an internal quantum yield η_i=85–95% were fabricated. In the continuous lasing mode of a diode laser with a 100-µm-wide aperture and a wavelength of 0.98 µm, the optical power output was as high as 6.5 W and was limited by the catastrophic optical degradation of mirrors. The radiation divergence in the plane normal to the p-n junction amounts to θ_⊥. The use of wide-gap waveguide layers, which deepens the potential electron well in the active region, is shown to reduce the temperature sensitivity of the InGaAs/GaAs/AlGaAs laser heterostructures in the temperature range from 0 to 70°C.     

p-Channel MOSFET's in LPCVD PolySilicon

p-channel MOSFET's have been fabricated in LPCVD polysilicon. A 5000-Å n⁺poly acts as the gate electrode on which a 500-Å thermal oxide is grown to act as the gate insulator. Then a 1500-Å LPCVD polysilicon layer is deposited at 620°C and is subsequently boron doped to form the conductive channel. Devices with channel length as small as 2 µm show well-behaved transistor characteristics. The drive current and leakage current are as suitable for usage as load element in memory applications. At large gate voltages the accumulation hole mobility is 9 cm²/V.s. The drain-to-source breakdown voltage exceeds -20 V.     

Ga0.4In0.6As/Al0.55In0.45As pseudomorphic modulation-doped field-effect transistors

High-performance pseudomorphic Ga0.4In0.6As/ Al0.55In0.45As modulation-doped field-effect transistors (MODFET's) grown by MBE on InP have been fabricated and characterized. DC transconductances as high as 271, 227, and 197 mS/mm were obtained at 300K for 1.6-µm and 2.9-µm gate-length enhancement-mode and 2-µm depletion-mode devices, respectively. An average electron velocity as high as 2.36 × 10⁷cm/s has been inferred for the 1.6-µm devices, which is higher than previously reported values for 1-µm gate-length Ga0.47In0.53As/Al0.48In0.52As MODFET's. The higher bandgap Al0.55In0.45As pseudomorphic barrier also offers the advantages of a larger conduction-band discontinuity and a higher Schottky barrier height.     

InGaAsP (λ=1.3 μm) strip buried heterostructure lasersgrown by MOCVD

The authors describe InGaAsP-InP index guides strip buried heterostructure lasers (SBH) operating at 1.3 μm with a 1.1-μm guiding layer grown by a two-step atmospheric pressure metalorganic chemical vapor deposition (MOCVD) growth procedure. These lasers are compared with buried heterostructure lasers having similar guiding layers under the active layer but terminated at the edge of the active layer. SBH lasers with 0.15-μm-thick active layer strips, 5-μm wide, and guide layers varying from 0 to 0.7 μm have threshold currents increasing from 34 to 59 mA, and nearly constant differential external quantum efficiencies of 0.2 mW/mA. The threshold current increases more rapidly with temperature with increasing guide layer thickness, with T₀ decreasing from 70°C for lasers without a guide layer to 54.3°C for lasers without a guide layer to 54.3°C for lasers with 0.7-μm-thick guide layers. Output powers of up to 30 mW/facet have been obtained from 254-μm-long lasers and were found to be insensitive to guide layer thickness     

Hybrid IRCCD imaging array

A hybrid IRCCD for high background application has been successfully fabricated. The device consists of fifty Hg0.7Cd0.3Te detector diodes of 50-µm × 50-µm sensitive areas and a silicon CCD maltiplexer with input circuits on 40-µm centers having bucket background subtraction and blooming protection circuits. The noise-equivalent power (NEP) of the IRCCD is 5 × 10^-14W-Hz^-1/2at background photon flux level of 4 × 10¹⁵photons . cm^-2s^-1, integration time of 2 × 10^-5s, and clock frequency of 3 × 10⁶Hz. The noise source of the detector diodes limits the IRCCD performance. The IRCCD is also evaluated with the real-time raster-scanned thermal images displayed on a CRT monitor. Two-dimensional images are generated by using a scanning mirror. A fixed-pattern noise is reduced by comparison of an object video to the reference video stored in a memory. A noise-equivalent temperature difference of the system is 0.6°C at a frame rate of 30 Hz. Instantaneous field of view is 1 mrad × 1 mrad and the field of view of the system is 12° × 5.7°.     

Boron ion implantation in silicon through selectively deposited tungsten films

The effect of implanting boron into silicon through thin selective tungsten films and annealing to form silicided p⁺-n junctions is investigated. A rate limited thickness of 0.011-µm tungsten is shown to have the equivalent stopping power of 0.08-µm oxide and be similarly ineffective in eliminating axial boron channeling. Nonetheless, junction diodes as shallow as 0.25µm with sheet resistances of 7 Ω, exhibiting nearly idealI-Vcharacteristics from -40 to 100°C, are fabricated. Analysis of the areal and perimeter leakage currents suggests that defects at the WSi2-SiO2interface are the contributing generation-recombination sites.     

GaAs MESFET's made by ion implantation into MOCVD Buffer layers

Low-noise GaAs metal-semiconductor field-effect transistors (MESFET's) have been made using ion-implanted metal organic chemical vapor deposition (MOCVD) buffer layers. A noise figure of 1.46 dB with 10.20 associated gain has been achieved at 12 GHz for a 0.5-µm gatelength by 300-µm gatewidth FET device. This result demonstrates that excellent GaAs LNFET's can be made by ion implantation into MOCVD buffer layers, comparable to the best results obtained from similar devices made by AsCl3vapor-phase epitaxy and molecular-beam epitaxy.     

High-power (AlGa)As strip-buried heterostructure lasers

The characteristics of index-guided strip-buried heterostructure lasers are described. The lasers are grown by a two-step process, consisting of the initial 5-layer planar growth by MOCVD, and after etching to define the strip buried wave guide, recovery by Al0.65Ga0.35As using LPE. The devices are highly uniform, having 20 mA thresholds, quantum efficiencies of 0.65, and T0of 163°C. The TE polarized emission was in the lowest order transverse mode and consisted of ∼ 6 longitudinal modes. CW output powers of 50 mW per facet were obtained from lasers with reduced output reflectivity, and pulsed powers of 95 mW per facet from uncoated lasers have been obtained. The far-field angular widths weresim 23degandsim 50degin, and perpendicular to the junction plane, respectively. The total optical conversion efficiency of the coated laser emitting 50 mW CW was 41.5 percent.     

A low-voltage high-speed silicon photodiode with buried isolation region for short-haul optical-fiber communications

A new epitaxial silicon p-i-n photodiode has been developed for short-haul optical-fiber communications that can be operated at biases as low as 4 V. The device has a heavily doped 5-µm-thick p⁺⁺isolation-region between the p⁺substrate and the π-epitaxial layer. Fast rise and fall times (2 ns), and low leakage current (40 pA) result from the recombination and trapping of the minority-carrier electrons in the substrate. Experimental results on such an n⁺-π-p⁺⁺-p⁺device with 1.1-mm²photosensitive area and 25-µm epi-layer thickness show quantum efficiency of 80 percent at 825-nm wavelength.     

High-Reliability Semiconductor Lasers for Optical Communications

InGaAsP/InP buried heterostructure (BH) lasers emitting at 1.3 μm have continued to operate stably for more than3.3 times 10^{4}h (3.8 years) at 50-60°C and at an output power of 5 mW/facet. A statistically estimated median lifetime exceeds 10⁶at 50°C. A relatively low activation energy of 0.32 eV is obtained for slow degradation. The saturable behavior of the aging characteristics is observed in many of the lasers. This mode is explained by the increased leakage current through the buried regions, and can be eliminated by electroluminescence (EL) mode aging at high temperature and current. Distributed feedback (DFB) lasers emitting at 1.55 μm are also subjected to accelerated aging at 60°C with a 3 mW/facet output after EL-mode aging. These DFB lasers demonstrate stable aging characteristics, for more than 2000 h of operating time being currently achieved.