High-performance back-illuminated InGaAs/InAlAs MSM photodetectorwith a record responsivity of 0.96 A/W

A high-performance back-illuminated In_0.53Ga_0.47 As/In_0.52Al_0.48As/InP metal-semiconductor-metal (MSM) detector is reported. A record responsivity of 0.96 A/W at 1.3-μm wavelength, corresponding to a quantum efficiency of 92%, was measured at 5 V and showed virtually no internal gain at 20 V. Packaged devices with 150-μm-diameter large detection area showed a 3-dB bandwidth of 4 GHz at 5 V with fiber pigtail butt-coupled package and 3.5 GHz with fiber pigtail silicon V-grooved package. Switching to front-illumination improves the bandwidth by 30-40% with 45-50% reduction of responsivity. Planar and mesa devices both show a low capacitance per unit area of 3.0 nF/cm² and dark current density of 5.6×10^-5 A/cm² at 5 V. Preliminary reliability test results show that the detector biased at 5 V survived temperature cycling of -35°C to 200°C, high-temperature burn-in at 125°C for 168 h and subsequent short-term accelerated aging at 200°C for 120 h without degradation     

Characteristics of GaAsSb single-quantum-well-lasers emitting near1.3 μm

We report data on GaAsSb single-quantum-well lasers grown on GaAs substrates. Room temperature pulsed emission at 1.275 μm in a 1250-μm-long device has been observed. Minimum threshold current densities of 535 A/cm² were measured in 2000-μm-long lasers. We also measured internal losses of 2-5 cm^-1, internal quantum efficiencies of 30%-38% and characteristic temperatures T₀ of 67°C-77°C. From these parameters, a gain constant G₀ of 1660 cm^-1 and a transparency current density J_tr of 134 A/cm² were calculated. The results indicate the potential for fabricating 1.3-μm vertical-cavity surface-emitting lasers from these materials     

1.1 kV 4H-SiC power UMOSFETs

Silicon Carbide (4H-SiC), power UMOSFETs were fabricated and characterized from room temperature to 200°C. The devices had a 12-μm thick lightly doped n-type drift layer, and a nominal channel length of 4 μm. When tested under Fluorinert^TM at room temperature, blocking voltages ranged from 1.0 kV to 1.2 kV. Effective channel mobility ranged from 1.5 cm²/V.s at room temperature with a gate bias of 32 V (3.5 MV/cm) up to 7 cm²/V.s at 100°C with an applied gate bias of 26 V (2.9 MV/cm). Specific on-resistance (R_on,sp) was calculated to be as low as 74 mΩ.cm² at 100°C under the same gate bias     

Electrical properties of Si p+-n junctions for sub-0.25μm CMOS fabricated by Ga FIB implantation

p⁺-n junction diodes for sub-0.25-μm CMOS circuits were fabricated using focused ion beam (FIB) Ga implantation into n-Si (100) substrates with background doping of N_b=(5-10)×10 ¹⁵ and N_b⁺=(1-10)×10¹⁷ cm^-3. Implant energy was varied from 2 to 50 keV at doses ranging from 1×10¹³ to 1×10¹⁵ cm^-2 with different scan speeds. Rapid thermal annealing (RTA) was performed at either 600 °C or 700°C for 30 s. Diodes fabricated on N_b⁺ with 10-keV Ga⁺ exhibited a leakage current (^I_R) 100× smaller than those fabricated with 50-keV Ga⁺. Tunneling was determined to be the major current transport mechanism for the diodes fabricated on N_b⁺ substrates. An optimal condition for I_R on N_b⁺ substrates was obtained at 15 keV/1×10¹⁵ cm^-2. Diodes annealed at 600°C were found to have an I_R 1000× smaller than those annealed at 700°C. I-V characteristics of diodes fabricated on N_b substrates with low-energy Ga⁺ showed no implant energy dependence. I-V characteristics were also measured as a function of temperature from 25 to 200°C. For diodes implanted with 15-keV Ga ⁺, the cross-over temperatures between I_diff and I_g-r occurred at 106°C for N_b ⁺ and at 91°C for N_b substrates     

1.57 μm strained-layer quantum-well GaInAlAs ridge-waveguidelaser diodes with high temperature (130°C) and ultrahigh-speed (17GHz) performance

The fabrication of GaInAlAs strained-layer (SL) multiple-quantum-well (MQW) ridge-waveguide (RW) laser diodes emitting at 1.57 μm is discussed. Due to an optimized layer structure, a very high characteristic temperature of 90 K was obtained. As a consequence for episide-up mounted devices, the maximum continuous wave (CW)-operation temperature is 130°C. At room temperature, a maximum output power of 47 mW was measured for 600-μm-long lasers with one high-reflection coated facet. The low series resistance of 4 Ω (2 Ω) for 200-μm-(400-μm)-long devices yields an ultrahigh 3-dB bandwidth of 17 GHz. These static and dynamic properties also result from a high internal quantum-efficiency of 0.83 and a high differential gain of 5.5×10^-15 cm²     

⟨110⟩-oriented GaAs MESFETs

GaAs metal semiconductor field-effect transistors (MESFETs) have been successfully fabricated on molecular-beam epitaxial (MBE) films grown on the off-axis (110) GaAs substrate. The (110) substrates were tilted 6° toward the (111) Ga face in order to produce device quality two-dimensional MBE growth. Following the growth of a 0.4-μm undoped GaAs buffer, a 0.18-μm GaAs channel with a doping density of 3.4×10¹⁷ cm^-3 and a 0.12-μm contact layer with a doping density of 2×10¹⁸ cm^-3, both doped with Si, were grown. MESFET devices fabricated on this material show very low-gate leakage current, low output conductance, and an extrinsic transconductance of 200 mS/mm. A unity-current-gain cutoff frequency of 23 GHz and a maximum frequency of oscillation of 56 GHz have been achieved. These (110) GaAs MESFETs have demonstrated their potential for high-speed digital circuits as well as microwave power FET applications     

High T0 long-wavelength InGaAsN quantum-well lasersgrown by GSMBE using a solid arsenic source

We demonstrate high performance, λ=1.3- and 1.4-μm wavelength InGaAsN-GaAs-InGaP quantum-well (QW) lasers grown lattice-matched to GaAs substrates by gas source molecular beam epitaxy (GSMBE) using a solid As source. Threshold current densities of 1.15 and 1.85 kA/cm² at λ=1.3 and 1.4 μm, respectively, were obtained for the lasers with a 7-μm ridge width and a 3-mm-long cavity. Internal quantum efficiencies of 82% and 52% were obtained for λ=1.3 and 1.4 μm emission, respectively, indicating that nonradiative processes are significantly reduced in the quantum well at λ=1.3 μm due to reduced N-H complex formation. These Fabry-Perot lasers also show high characteristic temperatures of T₀ =122 K and 100 K at λ=1.3 and 1.4 μm, respectively, as well as a low emission wavelength temperature dependence of (0.39±0.01) nm/°C over a temperature range of from 10°C to 60°C     

Effect of p-doping on the temperature dependence of differentialgain in FP and DFB 1.3-μm InGaAsP-InP multiple-quantum-well lasers

The temperature dependence of differential gain dG/dn for 1.3-μm InGaAsP-InP FP and DFB lasers with two profiles of p-doping was obtained from RIN measurements within the temperature range of 25°C-65°C. Experiments showed that the change of the active region doping level from 3·10¹⁷ cm^-3 to 3·10¹⁸ cm^-3 leads to a 50% increase of the differential gain for FP lasers at 25°C. Heavily doped devices also exhibit more rapid reduction of the differential gain with increasing temperature. The effect of active region doping on the energy separation between the electron Fermi level and electronic states coupled into the laser mode explains the observations. The temperature dependence of differential gain for DFB devices strongly depends on the detuning of the lasing wavelength from the gain peak     

High-temperature characteristic in 1.3-μm-range highly strainedGaInNAs ridge stripe lasers grown by metal-organic chemical vapordeposition

1.3-μm-range highly strained GaInNAs-GaAs double quantum-well ridge stripe lasers with different In contents (37% and 39%) grown by metal-organic chemical vapor deposition are demonstrated. The GaInNAs laser with In content of 37% emitting at 1.294 μm exhibited both a low threshold current density of 1.0 kA/cm² at 20°C and a high characteristic temperature of 148 K in the temperature range of 20°C-80°C     

Frequency stabilization of the sequence-band CO2 laserusing the 4.3-μm fluorescence method

The saturated 1.3-μm fluorescence stabilization method is applied to the 00⁰2-[10⁰1, 02⁰1]_I,II sequence band CO₂ laser transitions. For this purpose, the 4.3-μm fluorescence is observed using an external longitudinal CO₂ absorption cell heated to 300°C. The dependence of the frequency stability upon the gas temperature and pressure in the cell as well as laser parameters have been carried out in absolute frequency scale with the help of a two-channel heterodyne system. Under optimal conditions, the standard deviation of the beat note frequency between sequence band and regular band lasers for 30 s averaging time is less than 20 kHz, and the long-term stability and reproducibility is achieved at about 10 kHz     

High performance poly-Si TFTs fabricated using pulsed laserannealing and remote plasma CVD with low temperature processing

Key technologies for fabricating polycrystalline silicon thin film transistors (poly-Si TFTs) at a low temperature are discussed. Hydrogenated amorphous silicon films were crystallized by irradiation of a 30 ns-pulsed XeCl excimer laser. Crystalline grains were smaller than 100 nm. The density of localized trap states in poly-Si films was reduced to 4×10¹⁶ cm^-3 by plasma hydrogenation only for 30 seconds. Remote plasma chemical vapor deposition (CVD) using mesh electrodes realized a good interface of SiO ₂/Si with the interface trap density of 2.0×10¹⁰ cm^-2 eV^-1 at 270°C. Poly-Si TFTs were fabricated at 270°C using laser crystallization, plasma hydrogenation and remote plasma CVD. The carrier mobility was 640 cm²/Vs for n-channel TFTs and 400 cm²/Vs for p-channel TFTs. The threshold voltage was 0.8 V for n-channel TFTs and -1.5 V for p-channel TFTs. The leakage current of n-channel poly-Si TFTs was reduced from 2×10^-10 A/μm to 3×10^-13 A/μm at the gate voltage of -5 V using an offset gate electrode with an offset length of 1 μm     

Nitrogen-implanted SiC diodes using high-temperature implantation

6H-SiC diodes fabricated using high-temperature nitrogen implantation up to 1000°C are reported. Diodes were formed by RIE etching a 0.8-μm-deep mesa across the N⁺/P junction using NF₃/O₂ with an aluminum transfer mask. The junction was passivated with a deposited SiO₂ layer 0.6 μm thick. Contacts were made to N⁺ and P regions with thin nickel and aluminum layers, respectively, followed by a short anneal between 900 and 1000°C. These diodes have reverse-bias leakage at 25°C as low as 5×10^-11 A/cm² at 10 V     

High average power first-order distributed feedback quantum cascadelasers

We present distributed feedback quantum cascade lasers at 965 cm ^-1 with a high average optical output power at temperatures of up to 60°C. At a duty cycle of 3%, the averaged maximal output power of a 55-μm wide and 1.5-mm-long device at -30°C was 13.6 mW; at 60°C, the device emitted 2 mkV. Corresponding peak optical powers of 450 mW at -30°C and of 70 mW at 60°C have been observed. Due to the lateral current injection, we achieved single-mode behavior in a slightly distorted zero-order lateral mode across the whole range of investigated temperatures and output powers. At room temperature, the threshold current density was on the order of 6.7 kA/cm ²; the characteristic temperature T₀ was, due to tuning of the Bragg resonance into the gain curve, rather high, namely 310 K     

A versatile stacked storage capacitor on FLOTOX cell for megabitNVRAM's

A versatile stacked storage capacitor on FLOTOX (SCF) structure is proposed for a megabit nonvolatile DRAM (NV-DRAM) cell that has all the features required for NVRAMs. The SCF structure realizes a 30.94-μm ² NV-DRAM cell with 0.8-μm design rules and allows an innovative flash store/recall (DRAM to EEPROM/EEPROM to DRAM) operation that does not disturb original data in DRAM or EEPROM. This store operation is completed in less than 10 ms. The single cell shows excellent reliability such as store endurance greater than 10⁶ cycles and EEPROM data retention in excess of 10 years under high storage temperatures of 150°C and DRAM write operation at 85°C. The SCF cell has been successfully implemented into the 1 Mb NVRAM     

Low-resistance self-aligned Ti-silicide technology for sub-quartermicron CMOS devices

A low-resistance self-aligned Ti-silicide process featuring selective silicon deposition and subsequent pre-amorphization (SEDAM) is proposed and characterized for sub-quarter micron CMOS devices. 0.15-μm CMOS devices with low-resistance and uniform TiSi₂ on gate and source/drain regions were fabricated using the SEDAM process. Non-doped silicon films were selectively deposited on gate and source/drain regions to reduce suppression of silicidation due to heavily-doped As in the silicon. Silicidation was also enhanced by pre-amorphization, using ion-implantation, on the narrow gate and source/drain regions. Low-resistance and uniform TiSi₂ films were achieved on all narrow, long n⁺ and p⁺ poly-Si and diffusion layers of 0.15-μm CMOS devices. TiSi₂ films with a sheet resistance of 5 to 7 Ω/sq were stably and uniformly formed on 0.15-μm-wide n⁺ and p⁺ poly-Si. No degradation in leakage characteristics was observed in pn-junctions with TiSi₂ films. It was confirmed that, using SEDAM, excellent device characteristics were achieved for 0.15-μm NMOSFET's and PMOSFET's with self-aligned TiSi₂ films     

Stable operation (over 5000 h) of high-power 0.98-μm InGaAs-GaAsstrained quantum well ridge waveguide lasers for pumpingEr3+-doped fiber amplifiers

A maximum output power of 115 mW and a slope efficiency of 0.92 W/A have been achieved in 0.98-μm InGaAs strained quantum well lasers with a 3-μm-wide ridge waveguide structure for efficient fiber coupling. Stable operation of over 5000 h under 50°C constant power operation with an optical power density of 3.9 MW/cm² has been demonstrated with a degradation rate as low as 5×10^-6 per hour. These results show that this device is promising as a practical pumping source for Er³⁺-doped fiber optical amplifiers     

A floating CMOS bandgap voltage reference for differentialapplications

The circuit is suitable for precision mixed-mode systems using the differential approach, especially for the case of single-supply operation. An experimental prototype, realized in a 2-μm CMOS technology, generates a continuous-time low-impedance voltage of 2.48 V±24 mV before trimming. The temperature coefficient measured on 30 samples ranges from -20 to L32 p.p.m./°C in the temperature range from 0 to 100°C. Thanks to the differential approach, a high-frequency power supply rejection of -50 dB at 100 kHz was achieved. The active area of the chip is 1800 mil² and the circuit dissipates 6 mW when operated from a single 5-V supply     

A CMOS bandgap reference without resistors

This paper describes a bandgap reference fabricated in a 0.5-μm digital CMOS technology without resistors. The circuit uses ratioed transistors biased in strong inversion together with the inverse-function technique to produce a temperature-insensitive gain applied to the proportional to absolute temperature (PTAT) term in the reference. After trimming, the peak-to-peak output voltage change is 9.4 mV from 0°C to 70°C. It occupies 0.4 mm² and dissipates 1.4 mW from a 3.7-V supply     

Planar AlGaAs/GaAs heterojunction bipolar transistors fabricatedusing selective W-CVD

The authors describe a planar process for the AlGaAs/GaAs HBTs in which collector vias are buried selectively, even to the base layers, with chemical vapor deposited tungsten (CVD-W) films. By using WF₆ /SiH₄ chemistry, W could be deposited on Pt films, which were overlapped 50 nm thick on the AuGe-based collector electrodes, without depositing W on the surrounding SiO₂ layers. Current gains of planar HBTs with 3.5-μm×3.5-μm emitters were up to 150, for a collector current density of about 2.5×10⁴ A/cm²     

1.3-μm CW lasing characteristics of self-assembled InGaAs-GaAsquantum dots

This paper presents the lasing properties and their temperature dependence for 1.3-μm semiconductor lasers involving self-assembled InGaAs-GaAs quantum dots as the active region. High-density 1.3-μm emission dots were successfully grown by the combination of low-rate growth and InGaAs-layer overgrowth using molecular beam epitaxy. 1.3-μm ground-level CW lasing occurring at a low threshold current of 5.4 mA at 25°C with a realistic cavity length of 300 μm and high-reflectivity coatings on both facets. The internal loss of the lasers was evaluated to be about 1.2 cm^-1 from the inclination of the plots between the external quantum efficiency and the cavity length. The ground-level modal gain per dot layer was evaluated to be 1.0 cm^-1, which closely agreed with the calculation taking into account the dot density, inhomogeneous broadening, and homogeneous broadening. The characteristic temperature of threshold currents T₀ was found to depend on cavity length and the number of dot layers in the active region of the lasers. A T₀ of 82 K was obtained near room temperature, and spontaneous emission intensity as a function of injection current indicated that the nonradiative channel degraded the temperature characteristics. A low-temperature study suggested that an infinite T₀ with a low threshold current (~1 mA) is available if the nonradiative recombination process is eliminated. The investigation in this paper asserted that the improvement in surface density and radiative efficiency of quantum dots is a key to the evolution of 1.3-μm quantum-dot lasers