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1.
A GaAs Schottky-barrier with high quantum efficiency-bandwidth product has been developed by using a GaAs/Al0.25Ga0.75 As multilayer reflector. The multilayer reflector structure wa designed by using the scattering matrix method. By growing four pairs of Al0.25Ga0.75As (825 Å)/GaAs (330 Å) multilayer reflectors between the undoped GaAs active layer and the buffer layer, a responsivity of 0.6 A/W at λ=0.84 μm was obtained for this device. This represents a 30% improvement over the device without a multilayer reflector. The response speed of the photodiode was measured by the impulse response method, and the results yielded a rise time of 38.45 ps, corresponding to a bandwidth of 9 GHz for this detector  相似文献   

2.
We demonstrate, for the first time, the application of dopant-segregation (DS) technique in metal-germanium- metal photodetectors for dark-current suppression and high-speed performance. Low defect density and surface smooth epi-Ge (~300 nm) layer was selectively grown on patterned Si substrate using two-step epi-growth at 400degC/600degC combined with a thin (~10 nm) low-temperature Si/Si0.8 Ge0.2 buffer layer. NiGe with DS effectively modulates the Schottky barrier height and suppresses dark current to ~10 -7 A at -1 V bias (width/spacing: 30/2.5 mum). Under normal incidence illumination at 1.55 mum, the devices show photoresponsivity of 0.12 A/W. The 3 dB bandwidth under - 1 V bias is up to 6 GHz.  相似文献   

3.
In0.5Al0.5As/In0.5Ga0.5 As HEMTs have been grown metamorphically on GaAs substrates oriented 6° off (100) toward (111)A using a graded InAlAs buffer. The devices are enhancement mode and show good dc and RF performance. The 0.6-μm gate length devices have saturation currents of 262 mA/mm at a gate bias of 0.7 V and a peak transconductance of 647 mS/mm. The 0.6 μm×3 mm devices tested on-wafer have output powers up to 30 mW/mm and 46% power-added-efficiency (PAE) at 1 V drain bias and 850 MHz. When biased and matched for best efficiency performance, this same device has up to 68% PAE at Vd=1 V  相似文献   

4.
High-quality lead-salt-based Bragg mirror stacks were fabricated on BaF2(111) substrates by molecular beam epitaxy. The mirrors consisted of Pb1-xEuxTe quarter-wavelength layer pairs with 1% and 6% Eu content and were designed for use in mid-infrared (MIR) vertical emitting devices with a PbTe active zone. From theoretical simulations, we obtained the internal reflectivity with incidence from an active resonator medium and the reflectivity spectra of Bragg/metal mirror combinations. For a 32-layer pair mirror, we measured a record stopband reflectivity for the MIR of over 99% at 5.7 μm, in excellent agreement with our calculations  相似文献   

5.
We report on the demonstration of an intersubband (ISB) coupled quantum-well modulator operating at room temperature and telecommunication wavelength using a GaN-AIN quantum-well structure. The optical modulation is shown to result from electron tunneling between the wells. Stark shifting of the ISB absorption is observed. The maximum modulation depth is 0.79% at lambda= 2.3 mum and 0.18% at lambda= 1.37 mum for a mesa device with only 151-nm interaction length. We show that by reducing the mesa size down to 15 times 15 mum2, optical modulation bandwidth as large as 3 GHz can be obtained.  相似文献   

6.
Strained silicon-germanium (Si0.6Ge0.4) gated diodes have been fabricated and analyzed. The devices exhibit significantly enhanced gate-controlled tunneling current over that of coprocessed silicon control devices. The current characteristics are insensitive to measurement temperature in the 80 K to 300 K range. Independently extracted valence band offset at the strained Si0.6Ge0.4/Si interface is 0.4 eV, yielding a Si0.6Ge0.4 bandgap of 0.7 eV, which is much reduced compared to that of Si. The results are consistent with device operation based on quantum-mechanical band-to-band (BTB) tunneling rather than on thermal generation. Moreover, simulation of the strained Si0.6Ge0.4 device using a quantum-mechanical BTB tunneling model is in good agreement with the measurements.  相似文献   

7.
Self-aligned AlGaN/GaN high electron mobility transistors grown on semiinsulating SiC substrates with a 0.25 mum gate-length were fabricated using a single-step ohmic process. Our recently developed Mo/Al/Mo/Au-based ohmic contact requiring annealing temperatures between 500degC and 600degC was utilized. Ohmic contact resistances between 0.35-0.6 Omega ldr mm were achieved. These 0.25 mum gate-length devices exhibited drain current density as high as 1.05 A/mm at a gate bias of 0 V and a drain bias of 10 V. A knee voltage of less than 2 V and a peak extrinsic transconductance (gm ) of 321 mS/mm were measured. For their microwave characteristics, a unity gain cutoff frequency (fT ) of 82 GHz and maximum frequency of oscillation (f max) of 103 GHz were measured.  相似文献   

8.
This letter reports a novel approach to achieve low threshold voltage (Vt) Ni-fully-silicide (FUSI) nMOSFETs with SiON dielectrics. By using a dysprosium-oxide (Dy2O3) cap layer with a thickness of 5 Aring on top of the SiON host dielectrics, Vt,lin of 0.18 V for long-channel devices (Lg = 1 mum) using NiSi-FUSI electrode is obtained, satisfying the high-performance device requirements. The Vt modulation due to the Dy2O3 cap layer is also maintained in the short-channel devices (with an Lg,min of 90 nm as demonstrated in this letter). In particular, approximately 150times reduction in gate leakage current is seen while preserving the dielectric capacitance equivalent thickness after adding the Dy2O3 cap layer on SiON dielectrics, likely due to a high-k layer (DySiON) formation during device source/drain activation process. We also report that the Dy2O3 layer does not vitally degrade the device reliability, such as positive-bias temperature instability and time-dependant dielectrics breakdown.  相似文献   

9.
This paper describes the monolithic integration of InP HBTs and uni-traveling-carrier photodiodes (UTC-PDs) by nonselective regrowth. HBTs are fabricated from nonselectively regrown device layers and UTC-PD subcollector layers, which are grown first on a 3-in InP substrate. This makes it possible to optimize the layer design for the HBTs and UTC-PDs independently and minimize the interconnection between them. The fabricated HBTs have a collector thickness of 200 nm, and they show an ft of 260 GHz and an fmax of 320 GHz at a collector current density of 2.5 mA/mum2. The standard deviations of the ft and fmax across the wafer are 1.7% and 4.4%, respectively. The length of the interconnection between the HBTs and UTC-PDs can be made as small as 10 mum without any degradation of the regrown-HBT performance. The UTC-PDs fabricated on the same wafer exhibit a 3-dB bandwidth of 100 GHz and an output voltage of 1.0 V. There is no drawback in the performance of either device, as compared with that of discrete devices. We also demonstrate 100-GHz optical-input divide-by-two optoelectronic integrated circuits (OEICs) consisting of InP HBTs and a UTC-PD using this technique. These results indicate that the nonselective regrowth is promising for application toward over 100-Gb/s OEICs.  相似文献   

10.
A defect-free near-zero bird's beak, fully recessed oxide (FUROX) field-isolation technology has been evaluated through the fabrication of VLSI/nMOSFETs. The FUROX process mainly consists of: (1) a thin nitrided oxide as the stress buffer layer and the interface sealing layer for local oxidation enhancement; and (2) a novel more-reliable nitride masking structure for a two-step field oxidation and a self-aligned field implantation. The elimination of the necking effect on positive photoresist and the improvement of critical dimension control for polysilicon gates using the planarized isolation have been demonstrated. Through electrical characterization of n+-p diodes and field and active transistors, the FUROX devices have been shown to provide low leakage-current level, good isolation property, and large recovery of the effective channel width (1.4 μm). Therefore, the serious narrow-width effects that exist in conventional LOCOS (local oxidation of silicon) isolated have been effectively reduced. Using histogram analysis, the reliability of the masking structure had hence good uniformity of device properties for FUROX isolation have been exhibited. The successful fabrication of FUROX devices with Weff=0.6 μm clearly demonstrates that FUROX isolation technology is greatly superior to conventional LOCOS  相似文献   

11.
Quantum-dot infrared photodetectors have emerged as attractive devices for sensing long wavelength radiation. Their principle of operation is based on absorption of radiation via intersublevel transitions in quantum dots. Multiple layers of self-organized ln(Ga)As/Ga(Al)As quantum dots are generally incorporated in the active region of these devices. Three-dimensional quantum confinement allows normal incidence operation. This paper describes a novel variation in the design of these devices which allows a significant reduction of the dark current, high temperature operation and extension of operation to terahertz frequencies. The principle of operation and operating characteristics of this device - the tunnel quantum-dot intersublevel detector - are described. Operation is demonstrated from 6-80 mum at temperatures up to 300 K with acceptable values of peak responsivity (0.1-0.75 A/W) and specific detectivity (107-1011cm ldr Hz1/2/W-1 , depending on temperature and wavelength).  相似文献   

12.
The influeuce of mirror reflectivity on laser performance of InGaAs-GaAs vertical-cavity surface-emitting lasers fabricated by selective oxidation is investigated by the stepwise change of the number of pairs in top mirror stack after device fabrication. Devices with 18-pair stacks in the top mirror, which is the optimized number of pairs in this structure, show an output power over 1.9 mW and a slope efficiency of 55% while maintaining a low threshold current of 212 μA. The analysis of the threshold current and differential efficiency related to mirror reflectivity shows an internal quantum efficiency of 95%, an internal round-trip loss of 0.072, and a transparency current density of 71 A/cm2  相似文献   

13.
Long wavelength vertical-cavity semiconductor optical amplifiers   总被引:3,自引:0,他引:3  
This paper overviews the properties and possible applications of long wavelength vertical-cavity semiconductor optical amplifiers (VCSOAs). A VCSOA operating in the 1.3-μm wavelength region is presented. The device was fabricated using wafer bonding; it was optically pumped and operated in reflection mode. The reflectivity of the VCSOA top mirror was varied in the characterization of the device. Results are presented for 13 and 12 top mirror periods. By reducing the top mirror reflectivity, the amplifier gain, optical bandwidth, and saturation output power were simultaneously improved. For the case of 12 top mirror periods, rye demonstrate 13-dB fiber-to-fiber gain, 0.6 nm (100 GHz) optical bandwidth, a saturation output power of -3.5 dBm and a noise figure of 8.3 dB. The switching properties of the VCSOA are also briefly investigated. By modulating the pump laser, we have obtained a 46-dB extinction ratio in the output power, with the maximum output power corresponding to 7-dB fiber-to-fiber gain. All results are for continuous wave operation at room temperature  相似文献   

14.
Based on the continuity theorem of electric displacement including interface charges, the enhanced dielectric layer field (ENDIF) for silicon-on-insulator (SOI) high-voltage devices is proposed. The following three approaches for enhancing the dielectric layer electric field EI to increase the vertical breakdown voltage of a device VB,V are presented: 1) using a thin silicon layer with a high critical electric field ES,C ; 2) introducing a low-permittivity dielectric buried layer; and 3) implementing interface charges between the silicon and the dielectric layer. Considering the threshold energy of silicon epsivT, the formula of ES,C on silicon layer thickness tS is first obtained, which increases sharply with a decrease of tS, and reaches up to 141 V/mum at tS = 0.1 mum. Expressions for EI and VByV are given, which agree well with simulative and experimental results. Based on the ENDIF, the new device structures are given, and an EI value of 300 V/mum has been experimentally obtained for double-sided trench SOI. Moreover, several conventional SOI devices are explained well by ENDIF.  相似文献   

15.
The authors have grown long-wavelength distributed Bragg reflectors (DBRs), using alternating layers of the semiconductors AlSb and (Al,Ga)Sb, and measured their properties. The large refractive index ratio available with these materials allows for high-reflectivity mirrors with relative few mirror pairs. A simple 10-period AlSb/GaSb DBR had a maximum reflectivity of over 98% at a wavelength of 1.92 μm, and a 12-period Al0.2Ga0.8Sb/AlSb DBR exhibited reflectance greater than 99% at 1.38 μm. These structures are easily grown by molecular beam epitaxy (MBE) and are suitable for use in surface-normal photonic devices operating at long wavelengths  相似文献   

16.
We present metal-gate high-k-dielectric enhancement-mode (e-mode) III-V MOSFETs with the highest reported effective mobility and transconductance to date. The devices employ a GaGdO high-k (k = 20) gate stack, a Pt gate, and a delta-doped InGaAs/AlGaAs/GaAs hetero-structure. Typical 1-mum gate length device figures of merit are given as follows: saturation drive current, Id,sat = 407 muA/mum; threshold voltage, Vt = +0.26 V; maximum extrinsic transconductance, gm = 477 muS/mum (the highest reported to date for a III-V MOSFET); gate leakage current, Ig = 30 pA; subthreshold swing, S = 102 mV/dec; on resistance, Ron = 1920 Omega-mum; Ion/Ioff ratio = 6.3 x 104; and output conductance, gd = 11 mS/mm. A peak electron mobility of 5230 cm2/V. s was extracted from low-drain-bias measurements of 20 mum long-channel devices, which, to the authors' best knowledge, is the highest mobility extracted from any e-mode MOSFET. These transport and device data are highly encouraging for future high-performance n-channel complementary metal-oxide-semiconductor solutions based on III-V MOSFETs.  相似文献   

17.
A BST ferroelectric thin-film microwave phase shifter with interdigital capacitors on TiO2/Si substrate is presented. The interdigital capacitors have 230 mum signal width, 100 mum signal to ground gap, and 10 mum finger gap. The device, with phase shifts of 142deg and FoM of 107.3deg/dB applied voltage of 50 V at 16 GHz, has been realised. The TiO2 buffer layer grown by ALD enables successful integration of BST-based microwave tunable devices with Si wafer.  相似文献   

18.
An ECL 100K compatible 64/spl times/4 bit RAM with 6 ns access time, 600 mW power dissipation, and a chip size of 4.8 mm/SUP 2/ has been developed for caches and scratchpad memories to enhance the performance of high-speed computer systems. The excellent speed performance together with the high-packing density has been achieved by using an oxide isolation technology in conjunction with novel circuit techniques. The device is adaptable to modern subnanosecond logic arrays, and, hence, is a member of the Siemens SH 100 family.  相似文献   

19.
Based on a generalized circuit model for parallel-operated amplifiers with linear two-port devices, it has been proved that the S-parameter ratio S21/S12 and hence MSG (maximum stable gain) are invariant as long as the devices have an identical value of S21/S12 and the input and output networks are reciprocal. The invariance of K factor has been shown to hold for two cases: (i) devices are identical and input/output networks are lossless and symmetric with respect to each device, and (ii) identical admittances are added to the networks of case (i) so as to connect every device port with each other. Thus at least in these two cases, MAG (maximum available gain) and U (unilateral gain) are invariant as well as MSG under parallel operation of linear two-port devices. The invariance of S21/S12 and hence MSG applies to a variety of parallel-operated amplifiers such as distributed amplifiers and linear power amplifiers  相似文献   

20.
A new type of high-speed signal processing or analyzing device-the picosecond Fourier transformer-is proposed. The device can be used to obtain the Fourier transform of the time-dependent intensity of an optical signal. The device makes use of the spatially distributed electrooptic modulator or deflector, and has the potential for terahertz bandwidth and picosecond time resolution. Practical devices are considered and their performances (bandwidth, frequency resolution, etc.) are discussed. The operation of the proposed device is demonstrated in the microsecond range by a preliminary experiment using LiTaO3e-o deflectors.  相似文献   

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