Continuous-wave operation of GaInAs-AlGaAsSb quantum cascade lasers

We report on the demonstration of continuous-wave (CW) operation of GaInAs-AlGaAsSb quantum cascade (QC) lasers. By placing a 2.5-/spl mu/m-thick gold layer on both sides of the laser ridge to extract heat from the active region in the lateral direction, together with mounting the device epilayer down, we have achieved CW operation of GaInAs-AlGaAsSb QC lasers composed of 25 stages of active/injection regions. The maximum CW operating temperature of the lasers is 94 K, and the emission wavelength is around /spl lambda//spl sim/4.65 /spl mu/m. For a device with the size of 10/spl times/2000 /spl mu/m/sup 2/, the CW optical output power per facet is 13 mW at 42 K and 4 mW at 94 K. The CW threshold current density is 1.99 kA/cm/sup 2/ at 42 K, and 2.08 kA/cm/sup 2/ at 94 K, respectively.     

Demonstration of 1789 V, 6.68 m/spl Omega/ /spl middot/ cm/sup 2/ 4H-SiC merged-PiN-Schottky diodes

The design, fabrication and characterisation of a high performance 4H-SiC diode of 1789 V-6.6 A with a low differential specific-on resistance (R/sub SP/spl I.bar/ON/) of 6.68 m/spl Omega/ /spl middot/ cm/sup 2/, based on a 10.3 /spl mu/m 4H-SiC blocking layer doped to 6.6/spl times/10/sup 15/ cm/sup -3/, is reported. The corresponding figure-of-merit of V/sub B//sup 2//R/sub SP/spl I.bar/ON/ for this diode is 479 MW/cm/sup 2/, which substantially surpasses previous records for all other MPS diodes.     

Asymmetric broad waveguide diode lasers (/spl lambda/ = 980 nm) of large equivalent transverse spot size and low temperature sensitivity

980-nm InGaAs-InGaAsP diode lasers of asymmetric broad-waveguide (BW) transverse structure are demonstrated. Single-transverse-mode devices have equivalent (transverse) spot sizes of 0.8 /spl mu/m (i.e., significantly larger than for symmetric BW structures), which are obtained at no price in device-parameter temperature sensitivity. Built-in discrimination against the first-order transverse mode allows fundamental-transverse-mode operation in relatively narrow beams (/spl theta//sub /spl perp// = 34/spl deg/). For 2-mm-long 100-/spl mu/m-wide-stripe uncoated devices with double-quantum-well active regions, the threshold-current density is as low as 190 A/cm/sup 2/, while the characteristic temperatures for the threshold-current density T/sub 0/, and the external differential quantum efficiency T/sub 1/ are high: 183 K and 650 K, respectively.     

Room-temperature self-organised In/sub 0.5/Ga/sub 0.5/As quantum dot laser on silicon

The first room-temperature operation of In/sub 0.5/Ga/sub 0.5/As quantum dot lasers grown directly on Si substrates with a thin (/spl les/2 /spl mu/m) GaAs buffer layer is reported. The devices are characterised by J/sub th//spl sim/1500 A/cm/sup 2/, output power >50 mW, and large T/sub 0/ (244 K) and constant output slope efficiency (/spl ges/0.3 W/A) in the temperature range 5-95/spl deg/C.     

Electrical characteristics of 8-/spl Aring/ EOT HfO/sub 2//TaN low thermal-budget n-channel FETs with solid-phase epitaxially regrown junctions

The authors demonstrate high-performing n-channel transistors with a HfO/sub 2//TaN gate stack and a low thermal-budget process using solid-phase epitaxial regrowth of the source and drain junctions. The thinnest devices have an equivalent oxide thickness (EOT) of 8 /spl Aring/, a leakage current of 1.5 A/cm/sup 2/ at V/sub G/=1 V, a peak mobility of 190 cm/sup 2//V/spl middot/s, and a drive-current of 815 /spl mu/A//spl mu/m at an off-state current of 0.1 /spl mu/A//spl mu/m for V/sub DD/=1.2 V. Identical gate stacks processed with a 1000-/spl deg/C spike anneal have a higher peak mobility at 275 cm/sup 2//V/spl middot/s, but a 5-/spl Aring/ higher EOT and a reduced drive current at 610 /spl mu/A//spl mu/m. The observed performance improvement for the low thermal-budget devices is shown to be mostly related to the lower EOT. The time-to-breakdown measurements indicate a maximum operating voltage of 1.6 V (1.2 V at 125 /spl deg/C) for a ten-year lifetime, whereas positive-bias temperature-instability measurements indicate a sufficient lifetime for operating voltages below 0.75 V.     

Vertical-cavity surface-emitting lasers in the 8-/spl mu/m midinfrared spectral range with continuous-wave and pulsed emission

Continuous-wave (CW) as well as pulsed-laser emission from a midinfrared (/spl lambda/=7.92 /spl mu/m) IV-VI vertical-cavity surface-emitting laser at 1.8 K is presented. The high-finesse microcavity, containing PbSe as an active medium, was optically pumped with a carbon monoxide laser at a wavelength of 5.28 /spl mu/m (1894 cm/sup -1/) in either CW or Q-switched mode. The maximum achieved CW power was 4.8 mW and pulsed peak powers were up to 23 W. Linewidths are considerably narrower than 0.10 cm/sup -1/, corresponding to 0.6 nm.     

InGaAs/InP DHBTs with 120-nm collector having simultaneously high f/sub /spl tau//, f/sub max//spl ges/450 GHz

InP/In/sub 0.53/Ga/sub 0.47/As/InP double heterojunction bipolar transistors (DHBT) have been designed for increased bandwidth digital and analog circuits, and fabricated using a conventional mesa structure. These devices exhibit a maximum 450 GHz f/sub /spl tau// and 490 GHz f/sub max/, which is the highest simultaneous f/sub /spl tau// and f/sub max/ for any HBT. The devices have been scaled vertically for reduced electron collector transit time and aggressively scaled laterally to minimize the base-collector capacitance associated with thinner collectors. The dc current gain /spl beta/ is /spl ap/ 40 and V/sub BR,CEO/=3.9 V. The devices operate up to 25 mW//spl mu/m/sup 2/ dissipation (failing at J/sub e/=10 mA//spl mu/m/sup 2/, V/sub ce/=2.5 V, /spl Delta/T/sub failure/=301 K) and there is no evidence of current blocking up to J/sub e//spl ges/12 mA//spl mu/m/sup 2/ at V/sub ce/=2.0 V from the base-collector grade. The devices reported here employ a 30-nm highly doped InGaAs base, and a 120-nm collector containing an InGaAs/InAlAs superlattice grade at the base-collector junction.     

Room-temperature continuous-wave 1.55 /spl mu/m GaInNAsSb laser on GaAs

The first low-threshold 1.55 /spl mu/m lasers grown on GaAs are reported. Lasing at 1.55 /spl mu/m was observed from a 20/spl times/2400 /spl mu/m as-cleaved device with a room-temperature continuous-wave threshold current density of 579 A/cm/sup 2/, external efficiency of 41%, and 130 mW peak output power. The pulsed threshold current density was 550 A/cm/sup 2/ with >600 mW peak output power.     

High-performance 1.5 /spl mu/m GaInNAsSb lasers grown on GaAs

Substantially reduced threshold current density and improved efficiency in long-wavelength (>1.4 /spl mu/m) GaAs-based lasers are reported. A 20/spl times/1220 /spl mu/m as-cleaved device showed a room temperature continuous-wave threshold current density of 580 A/cm/sup 2/, external efficiency of 53%, and 200 mW peak output power at 1.5 /spl mu/m. The pulsed threshold current density was 450 A/cm/sup 2/ with 1145 mW peak output power.     

10-kV, 123-m/spl Omega//spl middot/cm/sup 2/ 4H-SiC power DMOSFETs

10-kV, 123-m/spl Omega//spl middot/cm/sup 2/ power DMOSFETs in 4H-SiC are demonstrated. A 42% reduction in R/sub on,sp/, compared to a previously reported value, was achieved by using an 8 /spl times/ 10/sup 14/ cm/sup -3/ doped, 85-/spl mu/m-thick drift epilayer. An effective channel mobility of 22 cm/sup 2//Vs was measured from a test MOSFET. A specific on-resistance of 123 m/spl Omega//spl middot/cm/sup 2/ were measured with a gate bias of 18 V, which corresponds to an E/sub ox/ of 3 MV/cm. A leakage current of 197 /spl mu/A was measured at a drain bias of 10 kV from a 4H-SiC DMOSFET with an active area of 4.24 /spl times/ 10/sup -3/ cm/sup 2/. A switching time of 100 ns was measured in 4.6-kV, 1.3-A switching measurements. This shows that the 4H-SiC power DMOSFETS are ideal for high-voltage, high-speed switching applications.     

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.     

Low threshold high-power room-temperature continuous-wave operation diode laser emitting at 2.26 /spl mu/m

Diode lasers emitting at 2.26 /spl mu/m, based on the InGaAsSb-AlGaAsSb materials system, are reported. These devices exhibit high internal quantum efficiency of 78% and low threshold current density of 184.5 A/cm/sup 2/ for a 2-mm-long cavity. Output power up to 700 mW (/spl ap/550 mW) has been obtained at 280 K (300 K) in continuous-wave operation with 100 /spl mu/m/spl times/1 mm lasers. These devices have been coated with an antireflection on the output facet and are mounted epilayer down on a copper block. The working temperature was maintained by a thermoelectric Peltier cooling element.     

High-temperature 4.5-/spl mu/m type-II quantum-well laser with Auger suppression

Laser emission at 4.2-4.5 /spl mu/m has been observed at temperatures up to 310 K in pulsed optical pumping experiments on type-II quantum-well (QW) lasers with four constituents in each period (InAs-Ga/sub 1-x/In/sub x/Sb-InAs-AlSb). The characteristic temperature, T/sub 0/, is 41 K, and a peak output power exceeding 2 W/facet is observed at 200 K. The power conversion efficiency per facet of /spl ap/0.2% up to 200 K is within a factor of 2 of the theoretical value. The 300 K Auger coefficient of 4/spl times/10/sup -27/ cm/sup 6//s extracted from the threshold pump intensity demonstrates that Auger losses have been suppressed by a factor of four.     

High mobility NMOSFET structure with high-/spl kappa/ dielectric

High-/spl kappa/ NMOSFET structures designed for enhancement mode operation have been fabricated with mobilities exceeding 6000 cm/sup 2//Vs. The NMOSFET structures which have been grown by molecular beam epitaxy on 3-in semi-insulating GaAs substrate comprise a 10 nm strained InGaAs channel layer and a high-/spl kappa/ dielectric layer (/spl kappa//spl cong/20). Electron mobilities of >6000 and 3822 cm/sup 2//Vs have been measured for sheet carrier concentrations n/sub s/ of 2-3/spl times/10/sup 12/ and /spl cong/5.85/spl times/10/sup 12/ cm/sup -2/, respectively. Sheet resistivities as low as 280 /spl Omega//sq. have been obtained.     

4H-SiC power bipolar junction transistor with a very low specific ON-resistance of 2.9 m/spl Omega//spl middot/cm/sup 2/

This letter reports a newly achieved best result on the specific ON-resistance (R/sub SP/spl I.bar/ON/) of power 4H-SiC bipolar junction transistors (BJTs). A 4H-SiC BJT based on a 12-/spl mu/m drift layer shows a record-low specific-ON resistance of only 2.9 m/spl Omega//spl middot/cm/sup 2/, with an open-base collector-to-emitter blocking voltage (V/sub ceo/) of 757 V, and a current gain of 18.8. The active area of this 4H-SiC BJT is 0.61 mm/sup 2/, and it has a fully interdigitated design. This high-performance 4H-SiC BJT conducts up to 5.24 A at a forward voltage drop of V/sub CE/=2.5 V, corresponding to a low R/sub SP-ON/ of 2.9 m/spl Omega//spl middot/cm/sup 2/ up to J/sub c/=859 A/cm/sup 2/. This is the lowest specific ON-resistance ever reported for high-power 4H-SiC BJTs.     

Low-frequency noise in submicrometer MOSFETs with HfO/sub 2/, HfO/sub 2//Al/sub 2/O/sub 3/ and HfAlO/sub x/ gate stacks

Low-frequency noise measurements were performed on p- and n-channel MOSFETs with HfO/sub 2/, HfAlO/sub x/ and HfO/sub 2//Al/sub 2/O/sub 3/ as the gate dielectric materials. The gate length varied from 0.135 to 0.36 /spl mu/m with 10.02 /spl mu/m gate width. The equivalent oxide thicknesses were: HfO/sub 2/ 23 /spl Aring/, HfAlO/sub x/ 28.5 /spl Aring/ and HfO/sub 2//Al/sub 2/O/sub 3/ 33 /spl Aring/. In addition to the core structures with only about 10 /spl Aring/ of oxide between the high-/spl kappa/ dielectric and silicon substrate, there were "double-gate oxide" structures where an interfacial oxide layer of 40 /spl Aring/ was grown between the high-/spl kappa/ dielectric and Si. DC analysis showed low gate leakage currents in the order of 10/sup -12/A(2-5/spl times/10/sup -5/ A/cm/sup 2/) for the devices and, in general, yielded higher threshold voltages and lower mobility values when compared to the corresponding SiO/sub 2/ devices. The unified number-mobility fluctuation model was used to account for the observed 1/f noise and to extract the oxide trap density, which ranged from 1.8/spl times/10/sup 17/ cm/sup -3/eV/sup -1/ to 1.3/spl times/10/sup 19/ cm/sup -3/eV/sup -1/, somewhat higher compared to conventional SiO/sub 2/ MOSFETs with the similar device dimensions. There was no evidence of single electron switching events or random telegraph signals. The aim of this paper is to present a general discussion on low-frequency noise characteristics of the three different high-/spl kappa//gate stacks, relative comparison among them and to the Si--SiO/sub 2/ system.     

InGaAs-InP mesa DHBTs with simultaneously high f/sub /spl tau// and f/sub max/ and low C/sub cb//I/sub c/ ratio

We report an InP-InGaAs-InP double heterojunction bipolar transistor (DHBT), fabricated using a conventional triple mesa structure, exhibiting a 370-GHz f/sub /spl tau// and 459-GHz f/sub max/, which is to our knowledge the highest f/sub /spl tau// reported for a mesa InP DHBT-as well as the highest simultaneous f/sub /spl tau// and f/sub max/ for any mesa HBT. The collector semiconductor was undercut to reduce the base-collector capacitance, producing a C/sub cb//I/sub c/ ratio of 0.28 ps/V at V/sub cb/=0.5 V. The V/sub BR,CEO/ is 5.6 V and the devices fail thermally only at >18 mW//spl mu/m/sup 2/, allowing dc bias from J/sub e/=4.8 mA//spl mu/m/sup 2/ at V/sub ce/=3.9 V to J/sub e/=12.5 mA//spl mu/m/sup 2/ at V/sub ce/=1.5 V. The device employs a 30 nm carbon-doped InGaAs base with graded base doping, and an InGaAs-InAlAs superlattice grade in the base-collector junction that contributes to a total depleted collector thickness of 150 nm.     

Ridge-width dependence on high-temperature continuous-wave quantum-cascade laser operation

We report continuous-wave (CW) operation of quantum-cascade lasers (/spl lambda/=6 /spl mu/m) up to a temperature of 313 K (40/spl deg/C). The maximum CW optical output powers range from 212 mW at 288 K to 22 mW at 313 K and are achieved with threshold current densities of 2.21 and 3.11 kA/cm/sup 2/, respectively, for a high-reflectivity-coated 12-/spl mu/m-wide and 2-mm-long laser. At room temperature (298 K), the power output is 145 mW at 0.87 A, corresponding to a power conversion efficiency of 1.68%. The maximum CW operating temperature of double-channel ridge waveguide lasers mounted epilayer-up on copper heatsinks is analyzed in terms of the ridge width, which is varied between 12 and 40 /spl mu/m. A clear trend of improved performance is observed as the ridge narrows.     

High-performance poly-Si TFTs made by Ni-mediated crystallization through low-shot laser annealing

High-performance polycrystalline silicon (poly-Si) thin-film transistors (TFTs) have been fabricated using metal-induced crystallization followed by laser annealing (L-MIC). Laser annealing after MIC was found to yield a major improvement to the electrical characteristics of poly-Si TFTs. At a laser fluence of 330 mJ/cm/sup 2/, the field effect mobility increased from 71 to 239 cm/sup 2//Vs, and the minimum leakage current reduced from around 3.0/spl times/10/sup -12/ A//spl mu/m to 2.9/spl times/10/sup -13/ A//spl mu/m at a drain voltage of 5 V. In addition, the dependence of the TFT characteristics on the laser energy density was much weaker than that for conventional excimer laser annealed poly-Si TFTs.     

Short wavelength (/spl lambda//spl sim/4.3 /spl mu/m) high-performance continuous-wave quantum-cascade lasers

We report continuous-wave (CW) operation of a 4.3-/spl mu/m quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-/spl mu/m-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm/sup 2/ is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 /spl mu/m at 80 K to 4.34 /spl mu/m at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26/spl deg/ and 49/spl deg/ in CW mode, respectively.