Long-wavelength In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As large-area avalanche photodiodes and arrays

Large-area (500-/spl mu/m diameter) mesa-structure In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APDs) are reported. The dark current density was /spl sim/2.5/spl times/10/sup -2/ nA//spl mu/m/sup 2/ at 90% of breakdown; low surface leakage current density (/spl sim/4.2 pA//spl mu/m) was achieved with wet chemical etching and SiO/sub 2/ passivation. An 18 /spl times/ 18 APD array with uniform distributions of breakdown voltage, dark current, and multiplication gain has also been demonstrated. The APDs in the array achieved 3-dB bandwidth of /spl sim/8 GHz at low gain and a gain-bandwidth product of /spl sim/120 GHz.     

Type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region

Operation of type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region has been demonstrated at temperatures up to 240 K in pulsed mode. These lasers fabricated with 150-/spl mu/m-wide mesa stripes operated in continuous-wave (CW) mode up to a maximum temperature of 110 K, with an output power exceeding 30 mW/f and a threshold current density of about 41 A/cm/sup 2/ at 90 K. The maximum CW operation temperature of 110 K is largely limited by the high specific thermal resistance of the 150-/spl mu/m-wide broad area lasers. A 20-/spl mu/m-wide mesa stripe laser was able to operate in CW mode at higher temperatures up to 125 K as a result of the reduced specific thermal resistance of a smaller device.     

Low thermal resistance high-speed top-emitting 980-nm VCSELs

Increasing copper plated heatsink radii from 0 to 4 /spl mu/m greater than the mesa in vertical-cavity surface-emitting lasers (VCSELs) reduced the measured thermal resistance for a range of device sizes to values 50% lower than previously reported over a range of device sizes. For a 9-/spl mu/m diameter oxide aperture, the larger heatsink increases output power and bandwidth by 131% and 40%, respectively. The lasers exhibit a 3-dB modulation frequency bandwidth up to 9.8 GHz at 10.5 kA/cm/sup 2/. The functional dependence of thermal resistance on oxide aperture diameter indicates the importance of lateral heat flow to mesa sidewalls.     

High-modal gain 1300-nm In(Ga)As-GaAs quantum-dot lasers

A semiconductor laser containing seven InAs-InGaAs stacked quantum-dot (QD) layers was grown by molecular beam epitaxy. Shallow mesa ridge-waveguide lasers with stripe width of 120 /spl mu/m were fabricated and tested. A high modal gain of 41 cm/sup -1/ was obtained at room temperature corresponding to a modal gain of /spl sim/6 cm/sup -1/ per QD layer, which is very promising to enable the realization of 1.3-/spl mu/m ultrashort cavity devices such as vertical-cavity surface-emitting lasers. Ground state laser action was achieved for a 360-/spl mu/m-cavity length with as-cleaved facets. The transparency current density per QD layer and internal quantum efficiency were 13 A/cm/sup 2/ and 67%, respectively.     

Very-low-threshold 2.4-/spl mu/m GaInAsSb-AlGaAsSb laser diodes operating at room temperature in the continuous-wave regime

A GaInAsSb-AlGaAsSb large optical cavity triple-quantum-well structure was grown by molecular-beam epitaxy. Shallow mesa ridge-waveguide lasers with stripe width of 100 /spl mu/m were fabricated and tested. An internal losses coefficient as low as 4 cm/sup -1/ and a high internal quantum efficiency of 70% were obtained. In the pulsed regime at room temperature, the extrapolated threshold current densities for infinite cavity length is 78 A/cm/sup 2/. The threshold current density per quantum well is as low as 34 A/cm/sup 2/ for a 3-mm-long cavity.     

A resonant tunneling quantum-dot infrared photodetector

A novel device-resonant tunneling quantum-dot infrared photodetector-has been investigated theoretically and experimentally. In this device, the transport of dark current and photocurrent are separated by the incorporation of a double barrier resonant tunnel heterostructure with each quantum-dot layer of the device. The devices with In/sub 0.4/Ga/sub 0.6/As-GaAs quantum dots are grown by molecular beam epitaxy. We have characterized devices designed for /spl sim/6 /spl mu/m response, and the devices also exhibit a strong photoresponse peak at /spl sim/17 /spl mu/m at 300 K due to transitions from the dot excited states. The dark currents in the tunnel devices are almost two orders of magnitude smaller than those in conventional devices. Measured values of J/sub dark/ are 1.6/spl times/10/sup -8/ A/cm/sup 2/ at 80 K and 1.55 A/cm/sup 2/ at 300 K for 1-V applied bias. Measured values of peak responsivity and specific detectivity D/sup */ are 0.063 A/W and 2.4/spl times/10/sup 10/ cm/spl middot/Hz/sup 1/2//W, respectively, under a bias of 2 V, at 80 K for the 6-/spl mu/m response. For the 17-/spl mu/m response, the measured values of peak responsivity and detectivity at 300 K are 0.032 A/W and 8.6/spl times/10/sup 6/ cm/spl middot/Hz/sup 1/2//W under 1 V bias.     

Edge-coupled InGaAs PIN photodiode with a light funnel waveguide

We have successfully fabricated InGaAs edge-coupled photodiodes (EC-PDs) with a light funnel integrated (LIFI) in front of the coupling aperture, called LIFI EC-PD, based on the self-terminated oxide polish (STOP), the crystallographic slope etching of InP, and the self-aligned diffusion (SAD) techniques. The LIFI EC-PD presents not only a lower dark current density (/spl sim/ 4.4 mA/cm/sup 2/) but also a higher responsivity (/spl sim/ 0.4 A/W) than that of the mesa EC-PD (27 mA/cm/sup 2/ and 0.26 A/W, respectively). Furthermore, the thick oxide film serves as the funnel in front of active-region aperture to enhance the coupling efficiency and to lower the bonding pad capacitance down to 50 fF. The lowered bonding pad capacitance can be beneficial in designing a device with a higher transit-time-limited frequency response of beyond 30 GHz. The LIFI EC-PD with a 1-/spl mu/m thick absorption layer exhibits a 3-dB bandwidth of 20 GHz and a responsivity of /spl sim/ 0.4 A/W.     

Novel hemispherical vertical cavity 1.3 mu m surface-emitting laser on semi-insulating substrate

A vertical cavity GaInAsP/InP surface-emitting laser at 1.3 mu m wavelength is demonstrated with a hemispherical cavity structure. The laser consists of a circular mesa buried (passivated) in polyimide and is made on a semi-insulating InP substrate. CW operation was obtained at 77 K with a threshold current density of 90 kA/cm/sup 2/.<>     

GaInAsSb/GaSb pn photodiodes for detection to 2.4 mu m

Ga/sub 0.77/In/sub 0.23/As/sub 0.20/Sb/sub 0.80//GaSb pn heterojunction photodiodes have been prepared by liquid phase epitaxy. They exhibit a long-wavelength threshold of 2.4 mu m. The room-temperature dark current at V=-0.5 V is 3 mu A (10 mA/cm/sup 2/) and the external quantum efficiency is around 40% in the wavelength range 1.75-2.25 mu m. The estimated detectivity D* at 2.2 mu m is 8.8*10/sup 9/ cm Hz/sup 1/2/ W/sup -1/.<>     

Low-threshold operation of 1.34-/spl mu/m GaInNAs VCSEL grown by MOVPE

Low-threshold operation was demonstrated for a 1.34-/spl mu/m vertical-cavity surface-emitting laser (VCSEL) with GaInNAs quantum wells (QWs) grown by metal-organic vapor-phase epitaxy. Optimizing the growth conditions and QW structure of the GaInNAs active layers resulted in edge-emitting lasers that oscillated with low threshold current densities of 0.87 kA/cm/sup 2/ at 1.34 /spl mu/m and 1.1 kA/cm/sup 2/ at 1.38 /spl mu/m, respectively. The VCSEL had a low threshold current of 2.8 mA and a lasing wavelength of 1.342 /spl mu/m at room temperature and operated up to 60/spl deg/C.     

Room temperature performance of low threshold 1.34-1.44-/spl mu/m GaInNAs-GaAs quantum-well lasers grown by molecular beam epitaxy

Room temperature lasing emission at 1.338 and 1.435 /spl mu/m with threshold current densities of 1518 and 1755 A/cm/sup 2/, respectively, is obtained in broad area GaInNAs-GaAs laser diodes (LDs) grown by molecular beam epitaxy. The 1.338-/spl mu/m LDs show a power output per facet up to 0.20 W/A, a characteristic temperature (T/sub 0/) of 78 K, and an external transparency current density (J/sub tr/) of 0.77 kA/cm/sup 2/. Increasing the lasing wavelength to 1.435 /spl mu/m results in a larger J/sub tr/ of 1.16 kA/cm/sup 2/ and a lower T/sub 0/ of 62 K, due to larger nonradiative recombination. However, the 1.435-/spl mu/m LDs still display a power output per facet up to 0.15 W/A, and a high internal quantum efficiency of 52%. These improved performances are achieved without the need to use strain compensation layers, Sb as a surfactant during the quantum-well growth, or a postgrowth thermal anneal cycle.     

Low-loss, high-voltage 6H-SiC epitaxial p-i-n diode

The p-i-n diodes were fabricated using 31 /spl mu/m thick n/sup -/- and p-type 6H-SiC epilayers grown by horizontal cold-wall chemical vapor deposition (CVD) with nitrogen and aluminum doping, respectively. The diode exhibited a very high breakdown voltage of 4.2 kV with a low on-resistance of 4.6 m/spl Omega/cm/sup 2/. This on-resistance is lower (by a factor of five) than that of a Si p-i-n diode with a similar breakdown voltage. The leakage current density was substantially lower even at high temperatures. The fabricated SiC p-i-n diode showed fast switching with a turn-off time of 0.18 /spl mu/s at 300 K. The carrier lifetime was estimated to be 0.64 /spl mu/s at 300 K, and more than 5.20 /spl mu/s at 500 K. Various characteristics of SiC p-i-n diodes which have an advantage of lower power dissipation owing to conductivity modulation were investigated.     

Wideband DHBTs using a graded carbon-doped InGaAs base

We report an InP/InGaAs/InP double heterojunction bipolar transistor (DHBT), fabricated using a mesa structure, exhibiting 282 GHz f/sub /spl tau// and 400 GHz f/sub max/. The DHBT employs a 30 nm InGaAs base with carbon doping graded from 8/spl middot/10/sup 19//cm/sup 3/ to 5/spl middot/10/sup 19//cm/sup 3/, an InP collector, and an InGaAs/InAlAs base-collector superlattice grade, with a total 217 nm collector depletion layer thickness. The low base sheet (580 /spl Omega/) and contact (<10 /spl Omega/-/spl mu/m/sup 2/) resistivities are in part responsible for the high f/sub max/ observed.     

Top-gate TFTs using 13.56 MHz PECVD microcrystalline silicon

Top-gate thin-film transistors (TFTs) with microcrystalline silicon (/spl mu/c-Si) channel layers deposited using standard 13.56 MHz plasma-enhanced chemical vapor deposition were fabricated at a maximum processing temperature of 250/spl deg/C. The TFTs employ amorphous silicon nitride (a-SiN) as the gate dielectric layer. The 80-nm-thick /spl mu/c-Si channel layer showed a dark conductivity of the order of 10/sup -7/ S/cm and a crystalline volume fraction of over 80%. The /spl mu/c-Si TFTs showed a field effect mobility of 0.85 cm/sup 2//V/spl middot/s, a threshold voltage of 4.8 V, a subthreshold slope of 1 V/dec, and an ON/OFF current ratio of /spl sim/10/sup 7/. More importantly, the TFTs were very stable under gate bias stress, offering promise for organic light-emitting display (OLED) applications.     

Interdigitated Ge p-i-n photodetectors fabricated on a Si substrate using graded SiGe buffer layers

We report an interdigitated p-i-n photodetector fabricated on a 1-/spl mu/m-thick Ge epitaxial layer grown on a Si substrate using a 10-/spl mu/m-thick graded SiGe buffer layer. A growth rate of 45 /spl Aring//s/spl sim/60 /spl Aring//s was achieved using low-energy plasma enhanced chemical vapor deposition. The Ge epitaxial layer had a threading dislocation density of 10/sup 5/ cm/sup -2/ and a rms surface roughness of 3.28 nm. The 3-dB bandwidth and the external quantum efficiency were measured on a photodetector having 1-/spl mu/m finger width and 2-/spl mu/m spacing with a 25/spl times/28 /spl mu/m/sup 2/ active area. At a wavelength of 1.3 /spl mu/m, the bandwidth was 2.2, 3.5, and 3.8 GHz at bias voltages of -1, -3, and -5 V, respectively. The dark current was 3.2 and 5.0 /spl mu/A at -3 and -5 V, respectively. This photodetector exhibited an external quantum efficiency of 49% at a wavelength of 1.3 /spl mu/m.     

Normal-incidence InAs self-assembled quantum-dot infrared photodetectors with a high detectivity

An InAs/AlGaAs quantum-dot infrared photodetector based on bound-to-bound intraband transitions in undoped InAs quantum dots is reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 /spl mu/m. At 77 K and -0.7 V bias, the responsivity was 14 mA/W and the detectivity, D*, was 10/sup 10/ cm/spl middot/Hz/sup 1/2//W.     

Fabrication of high-performance InGaAsN ridge waveguide lasers with pulsed anodic oxidation

We have demonstrated high-performance InGaAsN triple-quantum-well ridge waveguide (RWG) lasers fabricated using pulsed anodic oxidation. The lowest threshold current density of 675 A/cm/sup 2/ was obtained from a P-side-down bonded InGaAsN laser, with cavity length of 1600 /spl mu/m and contact ridge width of 10 /spl mu/m. The emission wavelength is 1295.1 nm. The transparency current density from a batch of unbonded InGaAsN RWG lasers was 397 A/cm/sup 2/ (equivalent to 132 A/cm/sup 2/ per well). High characteristic temperature of 138 K was also achieved from the bonded 10/spl times/1600-/spl mu/m/sup 2/ InGaAsN laser.     

A novel technique for fabricating high reliable trench DMOSFETs using self-align technique and hydrogen annealing

A novel technique for fabricating high reliability trench DMOSFETs using three mask layers is realized to obtain cost-effective production capability, higher cell density and current driving capability, and higher reliability. This technique provides a unit cell with 2.3/spl sim/2.4 /spl mu/m pitch and a channel density of 100 Mcell/in/sup 2/. Specific on-resistance is 0.36 m/spl Omega//spl middot/cm/sup 2/ with a blocking voltage of 43 V at a gate voltage of 10 V and 5 A source-to-drain current. The time to breakdown of gate oxide grown on the hydrogen annealed trench surface is much longer than that of oxide grown on a nonhydrogen annealed trench surface.     

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.     

Characteristics of Al/sub 2/O/sub 3//TiO/sub 2/ nanolaminates and AlTiO thin films on Si

This letter reports a metal-insulator-semiconductor structure based on Al/sub 2/O/sub 3//TiO/sub 2/ nanolaminates and AlTiO films evaporated on an unheated p-Si substrate. The structure exhibits a low hysteresis in the capacitance-voltage characteristics, a larger dielectric constant leading to a quantum mechanically corrected effective oxide thickness of 1.35-2.1 nm, good stability of the electrical characteristics to thermal processes, a large breakdown electric field of 7.5 MV/cm, and a leakage current density below 5/spl times/10/sup -7/ A/cm/sup 2/ at an electric field of 2 MV/cm.