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.     

A 1 cm/spl times/1 cm In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 1 cm/spl times/1 cm array of 100 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APD). The average breakdown voltage was 28.7 V with a standard deviation of less than 0.5 V. The distribution of breakdown voltage across the area followed a radial pattern consistent with a slight epitaxial growth nonuniformity. The mean dark current at a gain of 10, or 6.1 A/W, was 10.3 nA, and none of the 100 APDs had a dark current of more than 25 nA. The bandwidth at a gain of 10 was 6.2 GHz, and the maximum gain-bandwidth product was 140 GHz. This technology is ideally suited for next-generation three-dimensional imaging applications.     

12 W/mm AlGaN-GaN HFETs on silicon substrates

Al/sub 0.26/Ga/sub 0.74/N-GaN heterojunction field-effect transistors were grown by metal-organic chemical vapor deposition on high-resistivity 100-mm Si (111) substrates. Van der Pauw sheet resistance of the two-dimensional electron gas was 300 /spl Omega//square with a standard deviation of 10 /spl Omega//square. Maximum drain current density of /spl sim/1 A/mm was achieved with a three-terminal breakdown voltage of /spl sim/200 V. The cutoff frequency and maximum frequency of oscillation were 18 and 31 GHz, respectively, for 0.7-/spl mu/m gate-length devices. When biased at 50 V, a 2.14-GHz continuous wave power density of 12 W/mm was achieved with associated large-signal gain of 15.3 dB and a power-added efficiency of 52.7%. This is the highest power density ever reported from a GaN-based device grown on a silicon substrate, and is competitive with the best results obtained from conventional device designs on any substrate.     

Diamond FET using high-quality polycrystalline diamond with f/sub T/ of 45 GHz and f/sub max/ of 120 GHz

Using high-quality polycrystalline chemical-vapor-deposited diamond films with large grains (/spl sim/100 /spl mu/m), field effect transistors (FETs) with gate lengths of 0.1 /spl mu/m were fabricated. From the RF characteristics, the maximum transition frequency f/sub T/ and the maximum frequency of oscillation f/sub max/ were /spl sim/ 45 and /spl sim/ 120 GHz, respectively. The f/sub T/ and f/sub max/ values are much higher than the highest values for single-crystalline diamond FETs. The dc characteristics of the FET showed a drain-current density I/sub DS/ of 550 mA/mm at gate-source voltage V/sub GS/ of -3.5 V and a maximum transconductance g/sub m/ of 143 mS/mm at drain voltage V/sub DS/ of -8 V. These results indicate that the high-quality polycrystalline diamond film, whose maximum size is 4 in at present, is a most promising substrate for diamond electronic devices.     

Graded base type-II InP/GaAsSb DHBT with f/sub T/=475 GHz

The first demonstration of a type-II InP/GaAsSb double heterojunction bipolar transistor (DHBT) with a compositionally graded InGaAsSb to GaAsSb base layer is presented. A device with a 0.4/spl times/6 /spl mu/m/sup 2/ emitter dimensions achieves peak f/sub T/ of 475 GHz (f/sub MAX/=265 GHz) with current density at peak f/sub T/ exceeding 12 mA//spl mu/m/sup 2/. The structure consists of a 25-nm InGaAsSb/GaAsSb graded base layer and 65-nm InP collector grown by MBE with breakdown voltage /spl sim/4 V which demonstrates the vertical scaling versus breakdown advantage over type-I DHBTs.     

High breakdown voltage (Al/sub 0.3/Ga/sub 0.7/)/sub 0.5/In/sub 0.5/P/InGaAs quasi-enhancement-mode pHEMT with field-plate technology

A high breakdown voltage and a high turn-on voltage (Al/sub 0.3/Ga/sub 0.7/)/sub 0.5/In/sub 0.5/P/InGaAs quasi-enhancement-mode (E-mode) pseudomorphic HEMT (pHEMTs) with field-plate (FP) process is reported for the first time. Between gate and drain terminal, the transistor has a FP metal of 1 /spl mu/m, which is connected to a source terminal. The fabricated 0.5/spl times/150 /spl mu/m/sup 2/ device can be operated with gate voltage up to 1.6 V owing to its high Schottky turn-on voltage (V/sub ON/=0.85 V), which corresponds to a high drain-to-source current (I/sub ds/) of 420 mA/mm when drain-to-source voltage (V/sub ds/) is 3.5 V. By adopting the FP technology and large barrier height (Al/sub 0.3/Ga/sub 0.7/)/sub 0.5/In/sub 0.5/P layer design, the device achieved a high breakdown voltage of -47 V. The measured maximum transconductance, current gain cutoff frequency and maximum oscillation frequency are 370 mS/mm, 22 GHz , and 85 GHz, respectively. Under 5.2-GHz operation, a 15.2 dBm (220 mW/mm) and a 17.8 dBm (405 mW/mm) saturated output power can be achieved when drain voltage are 3.5 and 20 V. These characteristics demonstrate that the field-plated (Al/sub 0.3/Ga/sub 0.7/)/sub 0.5/In/sub 0.5/P E-mode pHEMTs have great potential for microwave power device applications.     

Dual-gate AlGaN/GaN modulation-doped field-effect transistors with cut-off frequencies f/sub T/>60 GHz

We demonstrate dual-gate AlGaN/GaN modulation-doped field-effect transistors (MODFETs) with gate-lengths of 0.16 /spl mu/m and 0.35 /spl mu/m for the first and second gates, respectively. The dual-gate device exhibits a current-gain cut-off frequency f/sub T/>60 GHz, and can simultaneously achieve a high breakdown voltage of >+100 V. In comparison to single-gate devices with the same gate length 0.16 /spl mu/m, dual-gate FETs can significantly increase breakdown voltages, largely increasing the maximum allowable drain bias for high power application. The continuous wave (CW) output power is in excess of 3.5 W/mm at 8.2 GHz. The corresponding large-signal gain is 12 dB and the power added efficiency is 45%. The dual-gate device with different gate lengths shows the capability of providing simultaneous high cut-off frequencies, and high breakdown voltages for broadband power amplifiers.     

DC and RF characteristics of E-mode Ga/sub 0.51/In/sub 0.49/P-In/sub 0.15/Ga/sub 0.85/As pseudomorphic HEMTs

The DC and RF characteristics of Ga/sub 0.49/In/sub 0.51/P-In/sub 0.15/Ga/sub 0.85/As enhancement- mode pseudomorphic HEMTs (pHEMTs) are reported for the first time. The transistor has a gate length of 0.8 /spl mu/m and a gate width of 200 /spl mu/m. It is found that the device can be operated with gate voltage up to 1.6 V, which corresponds to a high drain-source current (I/sub DS/) of 340 mA/mm when the drain-source voltage (V/sub DS/) is 4.0 V. The measured maximum transconductance, current gain cut-off frequency, and maximum oscillation frequency are 255.2 mS/mm, 20.6 GHz, and 40 GHz, respectively. When this device is operated at 1.9 GHz under class-AB bias condition, a 14.7-dBm (148.6 mW/mm) saturated power with a power-added efficiency of 50% is achieved when the drain voltage is 3.5 V. The measured F/sub min/ is 0.74 dB under I/sub DS/=15 mA and V/sub DS/=2 V.     

High-temperature thermal stability performance in /spl delta/-doped In/sub 0.425/Al/sub 0.575/As--In/sub 0.65/Ga/sub 0.35/As metamorphic HEMT

We report, to our knowledge, the best high-temperature characteristics and thermal stability of a novel /spl delta/-doped In/sub 0.425/Al/sub 0.575/As--In/sub 0.65/Ga/sub 0.35/As--GaAs metamorphic high-electron mobility transistor. High-temperature device characteristics, including extrinsic transconductance (g/sub m/), drain saturation current density (I/sub DSS/), on/off-state breakdown voltages (BV/sub on//BV/sub GD/), turn-on voltage (V/sub on/), and the gate-voltage swing have been extensively investigated for the gate dimensions of 0.65/spl times/200 /spl mu/m/sup 2/. The cutoff frequency (f/sub T/) and maximum oscillation frequency (f/sub max/), at 300 K, are 55.4 and 77.5 GHz at V/sub DS/=2 V, respectively. Moreover, the distinguished positive thermal threshold coefficient (/spl part/V/sub th///spl part/T) is superiorly as low as to 0.45 mV/K.     

60-GHz high power performance In/sub 0.35/Al/sub 0.65/As-In/sub 0-35/Ga/sub 0.65/As metamorphic HEMTs on GaAs

We report on a double-pulse doped, double recess In/sub 0.35/Al/sub 0.65/As-In/sub 0.35/Ga/sub 0.65/As metamorphic high electron mobility transistor (MHEMT) on GaAs substrate. This 0.15-/spl mu/m gate MHEMT exhibits excellent de characteristics, high current density of 750 mA/mm, extrinsic transconductance of 700 mS/mm. The on and off state breakdown are respectively of 5 and 13 V and defined It gate current density of 1 mA/mm. Power measurements at 60 GHz were performed on these devices. Biased between 2 and 5 V, they demonstrated a maximum output power of 390 mW/mm at 3.1 V of drain voltage with 2.8 dB power gain and a power added efficiency (PAE) of 18%. The output power at 1 dB gain compression is still of 300 mW/mm. Moreover, the linear power gain is of 5.2 dB. This is to our knowledge the best output power density of any MHEMT reported at this frequency.     

Metal-semiconductor-metal (MSM) photodetectors fabricated on MOCVD grown Hg/sub 1-x/Cd/sub x/Te

The fabrication of the first metal-semiconductor-metal photodetectors on Hg/sub 1-x/Cd/sub x/Te is reported using MOCVD grown layers on GaAs substrates. An epitaxial CdTe overlayer has been incorporated in the device structure for the enhancement of Schottky barrier characteristics. The interdigitated devices (2.3 mu m electrode width, 3.3 mu m spacing) exhibited a breakdown voltage of -60 V and responsivities of more than 1.0 A/W at a wavelength of 1.3 mu m and bias voltage of 40 V. Over the range of bias voltage examined, the dark leakage current of the detectors was dependent on the choice of contact metal, with minimum values of 10 nA at <1 V for Pt/CdTd/Hg/sub 1-x/Cd/sub x/Te.<>     

High-performance MIM capacitor using ALD high-k HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectrics

For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications.     

Evidence and understanding of ALD HfO/sub 2/-Al/sub 2/O/sub 3/ laminate MIM capacitors outperforming sandwich counterparts

Metal-insulator-metal capacitors with atomic-layer-deposited HfO/sub 2/-Al/sub 2/O/sub 3/ laminated and sandwiched dielectrics have been compared, for the first time, for analog circuit applications. The experimental results indicate that significant improvements can be obtained using the laminated dielectrics, including an extremely low leakage current of 1/spl times/10/sup -9/ A/cm/sup 2/ at 3.3V and 125/spl deg/C, a high breakdown electric field of /spl sim/3.3MV/cm at 125/spl deg/C, good polarity-independent electrical characteristics, while retaining relatively high capacitance density of 3.13 fF//spl mu/m/sup 2/ as well as voltage coefficients of capacitance as low as -80 ppm/V and 100 ppm/V/sup 2/ at 100 kHz. The underlying mechanism is likely due to alternate insertions of Al/sub 2/O/sub 3/ layers that reduce the thickness of each HfO/sub 2/ layer, hereby efficiently inhibiting HfO/sub 2/ crystallization, and blocking extensions of grain boundary channels from top to bottom as well as to achieve good interfacial quality.     

High-speed photoconductive switch based on low-temperature GaAs transferred on SiO/sub 2/-Si substrate

In this letter, we report high-speed photoconductive switches based on low-temperature (LT) grown GaAs on Si substrate. Epitaxially grown LT GaAs was separated from its substrate, transferred on an SiO/sub 2/-coated Si substrate and integrated with a transmission line. The 10/spl times/20-/spl mu/m/sup 2/ switches exhibit high breakdown voltage and low dark currents (<10/sup -7/ A at 100 V). The photoresponse at 810 nm shows electrical transients with /spl sim/0.55-ps full-width at half-maximum and /spl sim/0.37-ps decay time, both independent on the bias voltage up to the tested limit of 120 V. The photoresponse amplitude increases up to /spl sim/0.7 V with increased bias and the signal bandwith is /spl sim/500 GHz. The freestanding LT GaAs switches are best suited for ultrafast optoelectronic testing since they can be placed at virtually any point on the test circuit.     

A CMOS voltage reference based on weighted /spl Delta/V/sub GS/ for CMOS low-dropout linear regulators

A CMOS voltage reference, which is based on the weighted difference of the gate-source voltages of an NMOST and a PMOST operating in saturation region, is presented. The voltage reference is designed for CMOS low-dropout linear regulators and has been implemented in a standard 0.6-/spl mu/m CMOS technology (V/sub thn//spl ap/|V/sub thp/|/spl ap/0.9 V at 0/spl deg/C). The occupied chip area is 0.055 mm/sup 2/. The minimum supply voltage is 1.4 V, and the maximum supply current is 9.7 /spl mu/A. A typical mean uncalibrated temperature coefficient of 36.9 ppm//spl deg/C is achieved, and the typical mean line regulation is /spl plusmn/0.083%/V. The power-supply rejection ratio without any filtering capacitor at 100 Hz and 10 MHz are -47 and -20 dB, respectively. Moreover, the measured noise density with a 100-nF filtering capacitor at 100 Hz is 152 nV//spl radic/(Hz) and that at 100 kHz is 1.6 nV//spl radic/(Hz).     

DRAM plate electrode bias optimization for reducing leakage current in UV-O/sub 3/ and O/sub 2/ annealed CVD deposited Ta/sub 2/O/sub 5/ dielectric films

A new plate biasing scheme is described which allowed the use of 65% higher supply voltage without increasing the leakage current for the UV-O/sub 3/ and O/sub 2/ annealed chemical-vapor-deposited tantalum pentaoxide dielectric film capacitors in stacked DRAM cells. Dielectric leakage was reduced by biasing the capacitor plate electrode to a voltage lower than the conventionally used value of V/sub cc//2. Ta/sub 2/O/sub 5/ films with 3.9 nm effective gate oxide, 8.5 fF//spl mu/m/sup 2/ capacitance and <0.3 /spl mu/A/cm/sup 2/ leakage at 100/spl deg/C and 3.3 V supply are demonstrated.<>     

Influences of sulfur passivation on temperature-dependent characteristics of an AlGaAs/InGaAs/GaAs PHEMT

The influences of (NH/sub 4/)/sub 2/S/sub x/ treatment on an AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) are studied and demonstrated. Upon the sulfur passivation, the studied device exhibits better temperature-dependent dc and microwave characteristics. Experimentally, for a 1/spl times/100 /spl mu/m/sup 2/ gate/dimension PHEMT with sulfur passivation, the higher gate/drain breakdown voltage of 36.4 (21.5) V, higher turn-on voltage of 0.994 (0.69) V, lower gate leakage current of 0.6 (571) /spl mu/A/mm at V/sub GD/=-22 V, improved threshold voltage of -1.62 (-1.71) V, higher maximum transconductance of 240 (211) mS/mm with 348 (242) mA/mm broad operating regime (>0.9g/sub m,max/), and lower output conductance of 0.51 (0.53) mS/mm are obtained, respectively, at 300 (510) K. The corresponding unity current gain cutoff frequency f/sub T/ (maximum oscillation frequency f/sub max/) are 22.2 (87.9) and 19.5 (59.3) GHz at 250 and 400 K, respectively, with considerably broad operating regimes (>0.8f/sub T/,f/sub max/) larger than 455 mA/mm. Moreover, the relatively lower variations of device performances over wide temperature range (300/spl sim/510 K) are observed.     

Improvement of voltage linearity in high-/spl kappa/ MIM capacitors using HfO/sub 2/-SiO/sub 2/ stacked dielectric

It is demonstrated that the voltage coefficients of capacitance (VCC) in high-/spl kappa/ metal-insulator-metal (MIM) capacitors can be actively engineered and voltage linearity can be significantly improved maintaining high capacitance density, by using a stacked insulator structure of high-/spl kappa/ and SiO/sub 2/ dielectrics. A MIM capacitor with capacitance density of 6 fF/spl mu/m/sup 2/ and quadratic VCC of only 14 ppm/V/sup 2/ has been demonstrated together with excellent frequency and temperature dependence (temperature coefficients of capacitance of 54 ppm /spl deg/C) as well as low leakage current of less than 10 nA/cm/sup 2/ up to 4 V at 125 /spl deg/C.     

A 183 GHz f/sub T/ and 165 GHz f/sub max/ regrown-emitter DHBT with abrupt InP emitter

Small-area regrown emitter-base junction InP/In-GaAs/InP double heterojunction bipolar transistors (DHBT) using an abrupt InP emitter are presented for the first time. In a device with emitter-base junction area of 0.7 /spl times/ 8 /spl mu/m/sup 2/, a maximum 183 GHz f/sub T/ and 165 GHz f/sub max/ are exhibited. To our knowledge, this is the highest reported bandwidth for a III-V bipolar transistor utilizing emitter regrowth. The emitter current density is 6/spl times/10/sup 5/ A/cm/sup 2/ at V/sub CE,sat/ = 1.5 V. The small-signal current gain h/sub 21/ = 17, while collector breakdown voltage is near 6 V for the 1500-/spl Aring/-thick collector. The emitter structure, created by nonselective molecular beam epitaxy regrowth, combines a small-area emitter-base junction and a larger-area extrinsic emitter contact, and is similar in structure to that of a SiGe HBT. The higher f/sub T/ and f/sub max/ compared to previously reported devices are achieved by simplified regrowth using an InP emitter and by improvements to the regrowth surface preparation process.     

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.