Room-temperature 2.81-/spl mu/m continuous-wave operation of GaInAsSb-AlGaAsSb laser

GaInAsSb-AlGaAsSb multiple quantum-well (QW) lasers with an emission wavelength of 2.81 /spl mu/m are reported. The ridge waveguide lasers with highly strained QWs show continuous-wave laser emission up to 25/spl deg/C; in pulsed mode, the lasers operate up to 60/spl deg/C. For pulsed operation, a threshold current density of 360 A/cm/sup 2/ is found for devices with 30-/spl mu/m stripe width and 2-mm cavity length at room temperature. A low threshold current density at infinite length of 248 A/cm/sup 2/ is derived.     

Continuous-wave operation of GaInAsSb-GaSb type-II ridge waveguide lasers emitting at 2.8 /spl mu/m

We have realized compressively strained GaInAsSb-GaSb type-II double quantum-well lasers with an emission wavelength of 2.8 /spl mu/m. Using broad area devices, an internal absorption of 9.8 cm/sup -1/ and an internal quantum efficiency of 0.57 is determined. For the increase of the threshold current with temperature, a T/sub 0/ of 44 K is obtained. Narrow ridge waveguide lasers show continuous-wave laser operation at temperatures up to 45 /spl deg/C, with room-temperature (RT) threshold current of 37 mA. At RT, the maximum optical output power per facet of an uncoated 800/spl times/7 /spl mu/m/sup 2/ ridge waveguide laser exceeds 8 mW.     

High-power continuous-wave operation of quantum-cascade lasers up to 60/spl deg/C

High-temperature high-power continuous-wave (CW) operation of high-reflectivity-coated 12-/spl mu/m-wide quantum-cascade lasers emitting at /spl lambda/ = 6 /spl mu/m with a thick electroplated Au top contact layer is reported for different cavity lengths. For a 3-mm-long laser, the CW optical output powers of 381 mW at 293 K and 22 mW at maximum operating temperature of 333 K (60/spl deg/C) are achieved with threshold current densities of 1.93 and 3.09 kA/cm/sup 2/, respectively. At 298 K, the same cavity gives a maximum wall plug efficiency of 3.17% at 1.07 A. An even higher CW optical output power of 424 mW at 293 K is obtained for a 4-mm-long laser and the device also operates up to 332 K with an output power of 14 mW. Thermal resistance is also analyzed at threshold as a function of cavity length.     

Uncooled DBR laser directly Modulated at 3.125 gb/s as athermal transmitter for low-cost WDM systems

An uncooled three-section tunable distributed Bragg reflector laser is demonstrated as an athermal transmitter for low-cost uncooled wavelength-division-multiplexing (WDM) systems with tight channel spacing. A /spl plusmn/0.02-nm thermal wavelength drift is achieved under continuous-wave operation up to 70/spl deg/C. Dynamic sidemode suppression ratio of greater than 35 dB is consistently obtained under 3.125-Gb/s direct modulation over a 20/spl deg/C-70/spl deg/C temperature range, with wavelength variation of as low as /spl plusmn/0.2 nm. This indicates that more than an order of magnitude reduction in coarse WDM channel spacing is possible using this source.     

Continuous-wave operation of 5 /spl mu/m quantum cascade lasers with high-reflection coated facets

A report is presented on the continuous-wave operation of /spl lambda//spl sime/5 /spl mu/m GaInAs/AlInAs/InP-based quantum cascade lasers up to a heatsink temperature of 222 K (-51/spl deg/C). The devices are mounted epi-side down with high-reflection coated facets. The dissipated electrical power at threshold amounts to only 2.3 W at 222 K.     

Long wavelength GaInAsSb-AlGaAsSb distributed-feedback lasers emitting at 2.84 /spl mu/m

Room-temperature continuous-wave operation of a singlemode GaInAsSb/GaSb/AlGaAsSb distributed feedback (DFB) laser is presented at a record long emission wavelength for this material system of 2.843 /spl mu/m. The threshold current at 20/spl deg/C is 75 mA. Mode selection was realised by metal gratings laterally patterned to a ridge waveguide. By varying the grating period, DFB emission from 2.738 up to 2.843 /spl mu/m is obtained.     

Room-temperature CW operation of InGaAsP lasers on Si fabricated by wafer bonding

1.3-/spl mu/m InGaAsP-InP lasers have been successfully fabricated on Si substrates by wafer bonding with heat treatment at 400/spl deg/C. A pressure of 4 kg/cm/sup 2/ has been applied on the wafers before the heat treatment and this pressure application has enabled us to achieve bonding strength required for the device fabrication even when the bonding temperature is as low as 400/spl deg/C. Room-temperature continuous-wave operation with threshold current of 49 mA has been achieved for 7-/spl mu/m-wide mesa lasers.     

Room-temperature continuous-wave laser operation of electrically-pumped 1.55 /spl mu/m VECSEL

A report is presented on room-temperature (RT) continuous-wave (CW) laser emission at 1.55 /spl mu/m of an all InP-based electrically-pumped vertical external-cavity surface-emitting laser (EP-VECSEL). Threshold currents of 1.4 kA/cm/sup 2/ and output powers of up to 0.3 mW were measured under CW operation at RT. A maximum output power of 2.7 mW has been obtained in quasi-CW operation at a heatsink temperature of 10.5/spl deg/C. This first result demonstrates that EP-VECSELs are a potential candidate for the realisation of compact vertical-cavity emitting sources.     

1.50 /spl mu/m CW operation of GaInNAs/GaAs laser diodes grown by MOCVD

Room-temperature continuous-wave operation of a 1.5 /spl mu/m range GaInNAs laser grown by metal organic chemical vapour deposition is reported. The lasing wavelength of the GaInNAs/GaAs double quantum well laser was 1.50 /spl mu/m and the threshold current was 245 mA. The characteristic temperature between 10 and 50/spl deg/C was about 119 K under pulse operation.     

80/spl deg/C continuous-wave operation of 2.01-/spl mu/m wavelength InGaAlAs-InP vertical-cavity surface-emitting lasers

Electrically pumped buried tunnel junction InGaAlAs-InP vertical-cavity surface-emitting lasers (VCSELs) with self-adjusted lateral current and optical confinement and record emission wavelengths beyond 2 /spl mu/m are presented. Front and back side mirrors are realized using 31.5 epitaxial layer pairs of alternating InGaAs-InAlAs and a dielectric 2.5 pair CaF/sub 2/-a-Si layer stack. The devices show single-mode continuous-wave operation up to heat sink temperatures over 80/spl deg/C. The maximum output power at 20/spl deg/C reaches 0.43 mW, threshold current and voltage are as low as 0.66 mA and 0.73 V, respectively. To reach the long emission wavelength, we use an optimized active region comprising heavily strained quantum wells. High-resolution X-ray diffraction and photoluminescence measurements reveal excellent material quality without relaxation in the quantum wells.     

High-power vertical-cavity surface-emitting laser with an extra Au layer

We report the performance of a high-power vertical-cavity surface-emitting laser (VCSEL) with an extra Au layer. By using the extra Au layer, the far-field divergence angle from a 600-/spl mu/m diameter VCSEL device is suppressed from 30/spl deg/ to 15/spl deg/, and no strong sidelobe is observed in far-field pattern. There is a slight drop in optical output power due to the introduction of the extra Au layer. By improving the device packaging method, the VCSEL device produces the maximum continuous-wave optical output power of 1.95 W with lasing wavelength of 981.5 nm. The aging test is carried out under constant current mode at 60/spl deg/C, and the preliminary result shows that the total degradation of output power is less than 10% after 800 h.     

Continuous-wave operation of all-epitaxial InP-based 1.3 /spl mu/m VCSELs with 57% differential quantum efficiency

All-epitaxial InP-based 1.3 /spl mu/m VCSELs with a record-high continuous-wave differential quantum efficiency (57%) for single active region long-wavelength devices are demonstrated. Low-loss optical mode confinement is achieved through a selectively etched undercut tunnel-junction aperture. Singlemode continuous-wave lasing was observed up to 87/spl deg/C and the room-temperature output power was 1.1 mW at a current of 4.1 mA and a wavelength of 1.305 /spl mu/m.     

Room-temperature continuous-wave operation of GaInNAsSb laser diodes at 1.55 /spl mu/m

The first 1.55 /spl mu/m room-temperature continuous-wave (CW) operation of GaAs-based laser diodes utilising GaInNAsSb/GaNAs double quantum well active regions grown by molecular beam epitaxy is reported. In electrically-pumped CW operation the narrow ridge waveguide devices have a room temperature lasing wavelength of 1550 nm near threshold, increasing to 1553 nm at thermal rollover. The CW threshold current was 132 mA for a 3/spl times/589 /spl mu/m device, with a characteristic temperature of 83 K, measured in pulsed mode between 20 and 70/spl deg/C.     

Continuous-wave operation up to 36/spl deg/C of 1.3-/spl mu/m GaInAsP-InP vertical-cavity surface-emitting lasers

We introduced ion-beam assisted deposition in order to improve the quality of Al/sub 2/O/sub 3/ and SiO/sub 2/, which were used as part of the mirrors of 1.3-/spl mu/m GaInAsP-InP vertical-cavity surface-emitting lasers (VCSELs). The refractive index of Al/sub 2/O/sub 3/ was improved to 1.63 from 1.56 and the one of SiO/sub 2/ increased to 1.47 from 1.45. Low-threshold room-temperature continuous-wave (CW) operation of 1.3-/spl mu/m VCSEL with the improved mirrors was demonstrated. The threshold current was 2.4 mA at 20/spl deg/C. The CW operating temperature was raised to 36/spl deg/C, which is a record high temperature for 1.3-/spl mu/m VCSEL.     

Superlattice barrier 1528-nm vertical-cavity laser with 85/spl deg/C continuous-wave operation

We report 85/spl deg/C continuous-wave electrically pumped operation of a 1528-nm vertical-cavity laser. An InP-InGaAsP active region was wafer bonded to the GaAs-AlGaAs mirrors, with a superlattice barrier to reduce the defect density in the active region.     

Low-threshold continuous-wave 1.5-/spl mu/m GaInNAsSb lasers grown on GaAs

We present the first continuous-wave (CW) edge-emitting lasers at 1.5 /spl mu/m grown on GaAs by molecular beam epitaxy (MBE). These single quantum well (QW) devices show dramatic improvement in all areas of device performance as compared to previous reports. CW output powers as high as 140 mW (both facets) were obtained from 20 /spl mu/m /spl times/ 2450 /spl mu/m ridge-waveguide lasers possessing a threshold current density of 1.06 kA/cm/sup 2/, external quantum efficiency of 31%, and characteristic temperature T/sub 0/ of 139 K from 10/spl deg/C-60/spl deg/C. The lasing wavelength shifted 0.58 nm/K, resulting in CW laser action at 1.52 /spl mu/m at 70/spl deg/C. This is the first report of CW GaAs-based laser operation beyond 1.5 /spl mu/m. Evidence of Auger recombination and intervalence band absorption was found over the range of operation and prevented CW operation above 70/spl deg/C. Maximum CW output power was limited by insufficient thermal heatsinking; however, devices with a highly reflective (HR) coating applied to one facet produced 707 mW of pulsed output power limited by the laser driver. Similar CW output powers are expected with more sophisticated packaging and further optimization of the gain region. It is expected that such lasers will find application in next-generation optical networks as pump lasers for Raman amplifiers or doped fiber amplifiers, and could displace InP-based lasers for applications from 1.2 to 1.6 /spl mu/m.     

Enhancing leakage suppression in carbon-rich silicon junctions

Carbon-incorporated devices exhibit an increase in junction leakage relative to pure Si devices. The authors demonstrate that a leakage suppression of /spl sim/ 50 times can be achieved in carbon-rich (Si:C) junctions. This is accomplished by a prolonged annealing for 1 to 10 min at 850 /spl deg/C (much lower than typical annealing temperature of >1000/spl deg/C) and is attributed to a decrease in interstitial carbon concentration. After a 10-min annealing, the Si:C junctions display a leakage of 4/spl times/10/sup -13/ A//spl mu/m, which is much lower than that of 1050 /spl deg/C spike annealed Si junctions and well within the I/sub off/ requirements of low-standby-power device at the 45-nm node. Carbon-incorporated transistors with a gate length of 0.18 /spl mu/m exhibit an I/sub off/ reduction of /spl sim/ 10 times, compared to pure Si transistors, and both transistors have a similar subthreshold slope of 81 mV/dec.     

Thermally stable Ge/Ag/Ni Ohmic contact for InAlAs/InGaAs/InP HEMTs

Excellent annealed ohmic contacts based on Ge/Ag/Ni metallization have been realized in a temperature range between 385 and 500/spl deg/C, with a minimum contact resistance of 0.06 /spl Omega//spl middot/mm and a specific contact resistivity of 2.62 /spl times/10/sup -7/ /spl Omega//spl middot/cm/sup 2/ obtained at an annealing temperature of 425/spl deg/C for 60 s in a rapid thermal annealing (RTA) system. Thermal storage tests at temperatures of 215 and 250/spl deg/C in a nitrogen ambient showed that the Ge/Ag/Ni based ohmic contacts with an overlay of Ti/Pt/Au had far superior thermal stabilities than the conventional annealed AuGe/Ni ohmic contacts for InAlAs/InGaAs high electron mobility transistors (HEMTs). During the storage test at 215/spl deg/C, the ohmic contacts showed no degradation after 200 h. At 250/spl deg/C, the contact resistance value of the Ge/Ag/Ni ohmic contact increased only to a value of 0.1 /spl Omega//spl middot/mm over a 250-h period. Depletion-mode HEMTs (D-HEMTs) with a gate length of 0.2 /spl mu/m fabricated using Ge/Ag/Ni ohmic contacts with an overlay of Ti/Pt/Au demonstrated excellent dc and RF characteristics.     

Selective vapor-liquid-solid epitaxial growth of micro-Si probe electrode arrays with on-chip MOSFETs on Si (111) substrates

This paper reports on a fabrication technique for realizing micro-Si probe arrays with MOSFETs on the same Si substrate. Micro-Si probe arrays have been successfully fabricated on Si (111) substrates by selective vapor-liquid-solid (VLS) growth using catalytic Au dot arrays and Si/sub 2/H/sub 6/ used as the gas source for a molecular-beam-epitaxy. The Si probes can be grown at temperatures ranging from 500/spl deg/C to 700/spl deg/C. In this paper, MOSFETs were fabricated on Si (111) substrates and Au dots were placed at the drain regions of the MOSFETs in order to grow the Si probes. VLS growth at 700/spl deg/C for 2 h was carried out on these substrates. Consequently, the MOSFETs can be used in on-chip circuits for the VLS-Si probe array. The electrical characteristics of the MOSFETs were measured before and after the VLS process. After the VLS process, no changes in the MOSFET characteristics were observed due to the effects of Au-diffusion, and the results confirmed that VLS growth at a temperature of 700/spl deg/C allows fabrication of micro-Si probes without deterioration of the MOSFETs. VLS-Si probes with controlled conductance were realized. The as-grown Si probes were of high resistance, but could be changed to various conductivities by impurity diffusion.     

High-power ridge waveguide InGaAsN lasers fabricated with pulsed anodic oxidation

High-power InGaAsN triple-quantum-well strain-compensated lasers grown by metal-organic chemical vapor deposition were fabricated with pulsed anodic oxidation. A maximum light power output of 145 mW was obtained from a 4-/spl mu/m ridge waveguide uncoated laser diode in continuous-wave (CW) mode at room temperature. The devices operated in CW mode up to 130/spl deg/C with a characteristic temperature of 138 K in range of 20/spl deg/C-90/spl deg/C.