Submicron-square emitter AlGaAs/GaAs HBTs with AlGaAshetero-guardring

Successful operation of submicron-square emitter AlGaAs/GaAs HBTs is demonstrated for the first time by using a fully mesa-structure-type emitter-base junction-area definition method with an AlGaAs hetero-guardring. The hetero-guardring reduces surface recombination current at the emitter-mesa edge to 1.4 μA/μm. This is 1/10 of that for devices without the guardring. Here, dc gains of 20, 26, and 40 are achieved for 0.5 μm×0.5 μm, 0.7 μm×0.7 μm, and 0.9 μm×0.9 μm emitter HBTs, respectively. An f_T of 40 GHz, and an f_max of 30 GHz are obtained for 0.9 μm×0.9 μm at a J_C of 1.0×10⁵ A/cm²     

Emission characteristics of silicon vacuum triodes with fourdifferent gate geometries

Arrays of 10×10, 30×30, and 50×50 phosphorus-doped 0.005-0.025 Ω-cm, monocrystalline silicon field emitters have been fabricated with an emitter height of approximately 4.5 μm, a cone angle of 110°, and four gate openings ranging from 1.8 to 5.3 μm. The placement of the rims of the gates range from coplanar with the apexes of the emitters for the 1.8-μm devices to fully recessed for the 5.3-μm devices. The devices have been characterized in terms of geometry-dependent β factors, scaling of emission currents with array size, temperature dependency from room temperature to 48 K, pressure dependency from 2.5×10^-9 to 0.8×10^-5 torr, current fluctuations at room temperature and at 48 K, and image formation. All of the measurements have been performed by operating the devices in the gate-induced field emission mode     

Pulse operation and threshold characteristics of 1.55-μmInAlGaAs-InAlAs VCSELs

All-monolithic air-post index-guided vertical-cavity surface-emitting lasers have been demonstrated under pulsed electrical injection at room temperature. The structure grown in single step by metal-organic chemical vapor deposition employs InP lattice matched InAlAs/InAlGaAs Bragg mirrors and a 2λ-thick periodic gain active region with 15 InGaAs quantum wells (QWs). We report threshold current characteristics of these devices grown on a 2-in wafer with wide emission wavelength range of 1.51~1.59 μm. For the devices larger than 30-μm in diameter, we found the minimum threshold current density of ~2.93 kA/cm² at the emission wavelength of 1.57 μm, corresponding to about 20 nm wavelength offset between photoluminescence peak of InGaAs QWs and resonant cavity wavelength     

Sub-50-nm physical gate length CMOS technology and beyond usingsteep halo

Sub-50-nm CMOS devices are investigated using steep halo and shallow source/drain extensions. By using a high-ramp-rate spike annealing (HRR-SA) process and high-dose halo, 45-nm CMOS devices are fabricated with drive currents of 650 and 300 μA/μm for an off current of less than 10 nA/μm at 1.2 V with T_ox^inv =2.5 nm. For an off current less than 300 nA/μm, 33-nm pMOSFETs have a high drive current of 400 uA/μm. Short-channel effect and reverse short-channel effect are suppressed simultaneously by using the HRR-SA process to activate a source/drain extension (SDE) after forming a deep source/drain (S/D). This process sequence is defined as a reverse-order S/D (R-S/D) formation. By using this formation, 24-nm nMOSFETs are achieved with a high drive current of 800 μA/μm for an off current of less than 300 μA/μm at 1.2 V. This high drive current might be a result of a steep halo structure reducing the spreading resistance of source/drain extensions     

Direct measurement of lateral carrier leakage in 1.3-μm InGaAsPmultiple-quantum-well capped mesa buried heterostructure lasers

1.3-μm InGaAsP multiple-quantum-well (MQW) capped mesa buried heterostructure (CMBH) lasers with mesa widths ranging from 1 μm (standard single mode) to 100 μm (wide area) were fabricated on one wafer with identical current blocking layers at the sides. The single-mode devices had three times larger nominal threshold current density than the wide-area devices. Measurement of gain and loss in the devices showed the single-mode devices to have 6-8 cm^-1 higher loss and 40% lower optical confinement than the wide-area devices. Beyond these differences, the measurements show that up to 30% of the threshold current in the single-mode CMBH lasers does not contribute to the pumping of the MQW active region. Injection efficiency is measured to be close to unity for both single-mode and wide mesa devices. Scenarios to explain this parasitic current are discussed, including the potential role for nonradiative recombination centers at the regrown epitaxial interface, which can be consistent with all of the experimental results     

Performance enhancement of GaInP/GaAs heterojunction bipolarphototransistors using dc base bias

GaInP-GaAs heterojunction bipolar phototransistors grown by metal organic vapor phase epitaxy (MOVPE) and operated with frontside optical injection through the emitter are reported with high optical gain (<88) and record high frequency performance (28 GHz). Heteropassivation of the extrinsic base surface is employed using a depleted GaInP emitter layer between the nonself-aligned base contact and the emitter mesa. The phototransistor's performance is shown to improve with increasing dc base bias in agreement with predictions of a recently reported Gummel-Poon model. Experimental results are reported for devices with optical active areas of 10×10 μm², 20×20 μm², and 30×30 μm², with peak measured cutoff frequencies of 28.5, 23.1, and 18.5 GHz, respectively, obtained at collector current densities between 2×10 ³ and 6×10³ A/cm²     

High-power GaInAsSb-AlGaAsSb multiple-quantum-well diode lasersemitting at 1.9 μm

High-power diode lasers emitting at ~1.9 μm have been fabricated from a quantum-well heterostructure having an active region consisting of five GaInAsSb wells and six AlGaAsSb barriers. For devices 300 μm wide and 1000 μm long, single-ended output power as high as 1.3 W cw has been obtained with an initial differential quantum efficiency of 47%. The pulsed threshold current density is as low as 143 A/cm² for 2000-μm-long devices     

High-performance, 0.1 μm InAlAs/InGaAs high electron mobilitytransistors on GaAs

This letter describes the material characterization and device test of InAlAs/InGaAs high electron mobility transistors (HEMTs) grown on GaAs substrates with indium compositions and performance comparable to InP-based devices. This technology demonstrates the potential for lowered production cost of very high performance devices. The transistors were fabricated from material with room temperature channel electron mobilities and carrier concentrations of μ=10000 cm² /Vs, n=3.2×10¹² cm^-2 (In=53%) and μ=11800 cm²/Vs, n=2.8×10¹² cm^-2 (In=60%). A series of In=53%, 0.1×100 μm² and 0.1×50 μm² devices demonstrated extrinsic transconductance values greater than 1 S/mm with the best device reaching 1.074 S/mm. High-frequency testing of 0.1×50 μm² discrete HEMT's up to 40 GHz and fitting of a small signal equivalent circuit yielded an intrinsic transconductance (g_m,i) of 1.67 S/mm, with unity current gain frequency (f_T) of 150 GHz and a maximum frequency of oscillation (f_max) of 330 GHz. Transistors with In=60% exhibited an extrinsic g_m of 1.7 S/mm, which is the highest reported value for a GaAs based device     

High-speed performance of OMCVD grown InAlAs/InGaAs MSMphotodetectors at 1.5 μm and 1.3 μm wavelengths

A report is presented on the fabrication of high-speed In_0.53 Ga_0.47As metal-semiconductor-metal (MSM) photodetectors incorporating a high-quality lattice-matched InAlAs barrier enhancement layer, grown by organometallic chemical vapor deposition (OMCVD). Fast responses of ~55 ps full-width half-maximum at 1.5 μm and ~48 ps at 1.3 μm wavelengths are observed, corresponding to intrinsic device bandwidths of ~8 GHz and ~11 GHz, respectively. The absence of any tail to the pulse response, and of any low-bias DC gain, indicates a low-trap density at the InAlAs/InGaAs heterointerface. Bias independent dark currents of 10-20 μA are observed below breakdown, which occurred at >30 V in devices with a 500-A-thick InAlAs layer     

Fully-planar AlGaAs/GaAs HBT's achieved by selective CBE regrowth

This paper describes a novel fully planar AlGaAs/GaAs heterojunction bipolar transistor (HBT) technology using selective chemical beam epitaxy (CBE). Planarization is achieved by a selective regrowth of the base and collector contact layers. This process allows the simultaneous metallization of the emitter, base and collector on top of the device. For the devices with an emitter-base junction area of 2×6 μm² and a base-collector junction area of 14×6 μm², a current gain cut off frequency of 50 GHz and a maximum oscillation frequency of 30 GHz are achieved. The common emitter current gain h_FE is 25 for a collector current density J_c of 2×10⁴ A/cm²     

Quantum-dot microlasers

Edge-emitting short-cavity lasers with deeply-etched Bragg mirrors were fabricated on a GaInAs/AlGaAs laser structure with a single active layer of self-organised GaInAs quantum-dots. Continuous wave operation has been achieved down to cavity lengths of 16 μm with a minimum threshold current of 1.2 mA for 30 μm-long devices     

High reliability InGaP/GaAs HBT

Excellent long term reliability InGaP/GaAs heterojunction bipolar transistors (HBT) grown by metalorganic chemical vapor deposition (MOCVD) are demonstrated. There were no device failures (T=10000 h) in a sample lot of ten devices (L=6.4 μm ×20 μm) under moderate current densities and high-temperature testing (J_c=25 kA/cm ², V_ce=2.0 V, Junction Temp =264°C). The dc current gain for large area devices (L=75 μm ×75 μm) at 1 kA/cm² at a base sheet resistance of 240 ohms/sq (4×10 ¹⁹ cm^-3@700 Å) was over 100. The dc current gain before reliability testing (L=6.4 μm ×10 μm) at 0.8 kA/cm² was 62. The dc current gain (0.8 kA/cm²) decreased to 57 after 10000 h of reliability testing. The devices showed an f_T=61 GHz and f_max=103 GHz. The reliability results are the highest ever achieved for InGaP/GaAs HBT and these results indicate the great potential of InGaP/GaAs HBT for numerous low- and high-frequency microwave circuit applications. The reliability improvements are probably due to the initial low base current at low current densities which result from the low surface recombination of InGaP and the high valence band discontinuity between InGaP and GaAs     

High speed performance of 2-D vertical-cavity laser diode arrays

We have fabricated and tested 10×10 independently addressable vertical-cavity surface-emitting laser diode arrays. Arrays with 55 μm active diameter devices show an average threshold current density of 590 A/cm² and an excellent homogeneity of the output characteristics over the full array size with maximum CW output powers of 12 mW. Broad area laser diodes with active diameters of 75 μm reach output powers of 18 mW for CW operation and 180 mW under pulsed conditions. Small-signal modulation bandwidths are beyond 10 and 8 GHz for the 55 and 75 μm devices, respectively     

SiGe heterojunction bipolar transistors with thin α-Siemitters

A SiGe-base heterojunction bipolar transistor with an extremely thin n hydrogenated amorphous Si (α-Si:H) emitter is proposed and characterized. The structure results in enhanced emitter injection efficiency, current gain, and frequency performance. The fabricated devices exhibited maximum current gains of 100 and Early voltages of 55 V. The unity current gain cutoff frequency (f _T) for a device with an emitter size of 2 μm×4 μm was 8.5 GHz     

An in-system reprogrammable 32 K×8 CMOS flash memory

The authors describe the design and performance of a 192-mil² 256 K (32 K×8) flash memory targeted for in-system reprogrammable applications. Developed from a 1.5 μm EPROM base technology with a one-transistor 6×6-μm² cell, the device electrically erases all cells in the array matrix in 200 ms and electrically programs at the rate of 100 μs/byte typical. The read performance is equivalent to comparable-density CMOS EPROM devices with a chip-enable access time of 110 ns at 30-mA active current consumption. A command-port interface facilitates microprocessor-controlled reprogramming capability. Device reliability has been increased over byte-alterable EEPROMs by reducing the program power supply to 12 V. Cycling endurance experiments have demonstrated that the device is capable of more than 10000 erase/program cycles     

The enhancement of gate-induced-drain-leakage (GIDL) current inshort-channel SOI MOSFET and its application in measuring lateralbipolar current gain β

An off-state leakage current unique for short-channel SOI MOSFETs is reported. This off-state leakage is the amplification of gate-induced-drain-leakage current by the lateral bipolar transistor in an SOI device due to the floating body. The leakage current can be enhanced by as much as 100 times for 1/4 μm SOI devices. This can pose severe constraints in future 0.1 μm SOI device design. A novel technique was developed based on this mechanism to measure the lateral bipolar transistor current gain β of SOI devices without using a body contact     

Vertical cavity surface-emitting laser with an AlGaAs/AlAs Braggreflector

The letter elucidates the room temperature pulsed operation of a vertical cavity surface-emitting laser with an electrically conductive AlGaAs/AlAs distributed Bragg reflector (DBR). The maximum reflectivity of a DBR grown by MOCVD was 96% at 0.88 μm wavelength. The threshold current of 30 μm diameter devices was 200 mA under room temperature pulsed condition, which is the lowest value for such a broad area structure     

Submicrometer poly-Si CMOS fabrication with low-temperature laserdoping

The laser doping process for submicrometer CMOS devices with leakage currents as low as 10^-12 A/μm for both n-channel and p-channel devices is discussed. The I-V characteristics are comparable to those of poly-Si devices fabricated using ion implantation and high-temperature annealing processes. The laser-induced melting of predeposited impurity doping (LIMPID) process was used to fabricate submicrometer polycrystalline-Si CMOS devices. This process uses a very low temperature, so no dopant atom can diffuse along the grain boundaries in the solid region. The use of stacked Al/SiO₂ films as a protection layer made it possible to reduce the leakage current from several tens of picoamperes per micrometer to 1 pA/μm     

Role of neutral base recombination in high gain AlGaAs/GaAs HBT's

Neutral base recombination is a limiting factor controlling the maximum gain of AlGaAs/GaAs HBT's with base sheet resistances between 100 and 350 Ω/□. In this work, we investigate five series of AlGaAs/GaAs HBT growths in which the base thickness was varied between 500 and 1600 Å and the base doping level between 2.9× and 4.7×10¹⁹ cm^-3. The dc current gain of large area devices (L=75 μm×75 μm) varies by as much as a factor of two at high injection levels for a fixed base sheet resistance, depending on the growth optimization. One of these series (Series TA) has the highest current gains ever reported in this base sheet resistance range, with dc current gains over 225 (@ 200 A/cm² ) at a base sheet resistance of 330 Ω/□. A high dc current gain of 220 (@ 10 kA/cm²) was also confirmed in small area devices (L=8 μm×8 μm). High-frequency tests on a separate set of wafers grown under the same conditions indicate these high current gains can be achieved without compromising the RF characteristics: Both high and normal gain devices exhibit an f_t ~68 GHz and f_max~100 GHz. By fitting the base current as a sum of two components, one due to recombination in the neutral base and the other in the space charge region, we conclude that an improvement in the minority carrier lifetime is responsible for the observed increase in dc current gain. Moreover, we observe a thickness-dependent variation in the effective minority carrier lifetime as the gains increase, along with a nonlinear dependence of current gain on base doping. Both phenomena are discussed in terms of an increase in Auger and radiative recombination relative to Hall-Shockley-Read recombination in optimized samples     

Low-loss low-confinement GaAs-AlGaAs DQW laser diode with opticaltrap layer for high-power operation

A low-confinement asymmetric GaAs-AlGaAs double-quantum-well molecular-beam-epitaxy grown laser diode structure with optical trap layer is characterized, The value of the internal absorption coefficient is as low as 1.4 cm^-1, while keeping the series resistance at values comparable cm with symmetrical quantum-well gradient index structures in the same material system. Uncoated devices show COD values of 35 mW/μm. If coated, this should scale to about 90 mW/μm. The threshold current density is about 1000 A/cm² for 2-mm-long devices and a considerable part of it is probably due to recombination in the optical trap layer. Fundamental mode operation is limited to 120-180 mW for 6.5-μm-wide ridge waveguide uncoated devices and to 200-300 mW for 13.5-μm-wide ones, because of thermal waveguiding effects. These values are measured under pulsed conditions, 10 μs/l ms