High-speed InGaP/GaAs HBTs with a strained InxGa1-xAs base

A self-aligned InGaP/GaAs heterojunction bipolar transistor with a compositionally graded In_xGa_1-xAs base has been demonstrated with f_T=83 GHz and f_max=197 GHz. To our knowledge, these results are the highest reported for both parameters in InGaP/GaAs HBT's. The graded base, which improves electron transport through the base, results in a DC current gain and a cutoff frequency which are 100% and 20% higher, respectively, than that achieved by an identical device with a nongraded base. The high f_max results from a heavily doped base, self-aligned base contacts, and a self-aligned collector etch. These results demonstrate the applicability of InGaP/GaAs HBT's in high-speed microwave applications     

Heavily carbon-doped InGaP/GaAs HBT's with buried polycrystallineGaAs under the base electrode

This paper describes a new approach to fabricating InGaP/GaAs heterojunction bipolar transistors (HBT's) with a high cutoff frequency (f_T), high maximum oscillation frequency (f_max), and low external collector capacitance (C_bc). To attain a high f_T and f_max, a heavy carbon-doping (1.3×10²⁰ cm^-3) technique was used with a thin (30-nm-thick) GaAs base layer, while for low C_bc, low-temperature gas-source molecular-beam epitaxial growth on SiO₂ -patterned substrates was used to bury high-resistance polycrystalline GaAs under the base electrode. An f_T of 120 GHz and an f_max of 230 GHz were achieved for three parallel 0.7×8.5 μm HBT's with an undoped-collector structure, and an f _T of 170 GHz and an f_max of 160 GHz were obtained for a single 0.9×10 μm HBT with a ballistic-collection-transistor structure. Compared to HBT's without buried poly-GaAs, the maximum stable gain was improved by 1.2 dB in the 0.7×8.5 μm HBT and by 2.3 dB in the 0.9×10 μm HBT due to the reduction in C_bc. These results show the high potential of the proposed HBT's for high-speed digital and broadband-amplifier applications     

112-GHz collector-up Ge/GaAs heterojunction bipolar transistorswith low turn-on voltage

This paper reports small-sized collector-up Ge/Ga/As heterojunction bipolar transistors (HBT's) operating at low power and high frequency. A heavily B-doped Ge base-layer and a newly-developed self-aligned process reduce the base resistance and the parasitic elements. Intrinsic base resistance is 50 Ω/□; this is the lowest value reported for bipolar transistors. With limiting the active emitter area through B ion implantation, these collector-up HBT's with a collector size of 2×5 μm² exhibit a current gain of 60. They exhibit a maximum oscillation frequency f_max of 112 GHz with an associated current gain cutoff frequency f_T of 25 GHz. The large value of f_max, exceeding 100 GHz, is attributed to the extremely low base resistance caused by the heavily B-doped base-layer and the self-aligned process and to the low base-collector capacitance expected from the collector-up structure. The turn-on voltage of these HBT's is approximately 0.7 V smaller than that of AlGaAs/GaAs HBT's. These results show that these HBT's have excellent potential for low-power dissipation circuits     

InGaP/InGaAs HFET with high current density and high cut-offfrequencies

Doped channel pseudomorphic In_0.49Ga_0.51P/In _0.20Ga_0.80As/GaAs heterostructure field effect transistors have been fabricated on GaAs substrate with 0.25 μm T-gates and self-aligned ohmic contact enhancement. By introducing the channel doping and reducing the series resistances, a high current density of 500 mA/mm is obtained in combination with cut off frequencies of f_T=68 GHz and f_max=160 GHz. The channel doping did not affect the RF-performance of the device essentially, which is additionally reflected in noise figures below 1.0 dB with an associated gain of 14.5 dB at 12 GHz     

DC, RF, and noise characteristics of carbon-doped base InP/InGaAsheterojunction bipolar transistors

The first successful demonstration of high-performance InP/InGaAs heterojunction bipolar transistors utilizing a highly carbon-doped base is reported. The detailed device characteristics including dc, RF, and noise performance have been investigated. For the first time base layers free of hydrogen passivation have been obtained using chemical beam epitaxy. The HBT's showed almost ideal dc characteristics; a gain independent of collector current, a near unity ideality factor, a very small offset-voltage, and a high breakdown voltage. Devices having two 1.5 μm×15 μm emitter fingers exhibited a maximum f_T of 115 GHz and f_max of 52 GHz. The device also exhibited a minimum noise figure of 3.6 dB and associated gain of 13.2 dB at a collector current level of 2 mA where a f_T of 29 GHz and f_max of 23 GHz were measured. The nearly ideal dc characteristics, excellent speed performance, and RF noise performance demonstrate the great potential of the carbon-doped base InP/InGaAs HBT's     

High-speed InGaP/GaAs heterojunction bipolar transistors withburied SiO2 using WSi as the base electrode

High-speed InGaP/GaAs heterojunction bipolar transistors (HBT's) with a small emitter area are described. WSi is used as the base electrode to fabricate HBT's with a narrow base contact width and a buried SiO₂ structure. An HBT with an emitter area of 0.8×5 μm exhibited an f_T of 105 GHz and an f_max of 120 GHz. These high values are obtained due to the reduction of C_BC by using buried SiO₂ with a narrow base contact width, indicating the great potential of GaAs HBT's for high-speed and low-power circuit applications     

High-speed InGaP/GaAs transistors with a sidewall base contactstructure

We have fabricated InGaP/GaAs double heterojunction bipolar transistors with a sidewall base contact structure. These transistors operate in both emitter-up and emitter-down modes. Symmetric characteristics of the cutoff frequency f_T=68 GHz and the maximum oscillation frequency f_max=31 GHz were obtained at a base-collector bias V_BC of 0 V. For emitter-down operation, f _T was found to reach a maximum of 78 GHz when the base-collector junction was forward biased at 0.9 V. The product of f _T for emitter-down operation and f_T for emitter-up operation was 5.3×10³ GHz², which is about six times that of previously reported SiGe heterojunction bipolar transistors     

High frequency performance of SiC heterojunction bipolartransistors

A compact heterojunction bipolar transistor (HBT) model was employed to simulate the high frequency and high power performances of SiC-based bipolar transistors. Potential 6H-SiC/3C-SiC heterojunction bipolar transistors (6H/3C-HBT's) at case temperatures of 27°C (300 K) through 600°C (873 K) were investigated. The high frequency and high power performance was compared to AlGaAs/GaAs HBT's. As expected, the ohmic contact resistance limits the high frequency performance of the SiC HBT. At the present time, it is only possible to reliably produce 1×10^-4 Ω-cm² contact resistances on SiC, so an f_T of 4.4 GHz and an f_max of 3.2 GHz are the highest realistic values. However, assuming an incredibly low 1×10^-6 Ω-cm² contact resistance for the emitter, base, and collector terminals, an f_T of 31.1 GHz and an f_max of 12.7 GHz can be obtained for a 6H/3C-SiC HBT     

Proposal of low-noise amplifier utilizing resonant tunnelingtransistors

A low-noise amplifier utilizing the negative input resistance of resonant tunneling transistors (RTT's) is proposed. Expected features of the RTT amplifiers are: 1) negligible effect of noise sources at the output, owing to their large power gain; 2) flat variation of noise figure (NF) versus frequency, due to white spectra of noise sources at the input; and 3) a high maximum oscillation frequency (f_max) (over several 100 GHz), Based on simulated DC characteristics, over 500 GHz f_max and 0.3 dB NF at 100 GHz are predicted for optimized AlGaAs/GaAs/AlGaAs resonant tunneling diodes (RTD's). In an RTT formed by coupling an FET to an optimized RTD, 0.55 dB minimum noise figure and 26 dB associated gain are predicted at 100 GHz. Also, a 1/w² spectrum of the input noise resistance is predicted at low frequencies     

High-speed InGaP/GaAs HBTs using a simple collector undercuttechnique to reduce base-collector capacitance

High-speed InGaP/GaAs HBTs were fabricated using a simple collector undercut (CU) technique to physically remove the collector material underneath the extrinsic base region by selective etching for reducing base-collector capacitance (C_BC). The best HBTs achieved a f_T of 80 GHz and a f_max (MSG/MAG) of 171 GHz. To our knowledge, this is the highest f_max (MSG/MAG) ever reported for the InGaP/GaAs HBTs. Compared to the HBTs without CUs, the CU HBTs showed a factor of 1.38 times improvement in the highest achievable f_max (MSG/MAG) due to the significant reduction of the C_BC     

High performance 0.1 μm gate-length p-type SiGe MODFET's andMOS-MODFET's

High performance p-type modulation-doped field-effect transistors (MODFET's) and metal-oxide-semiconductor MODFET (MOS-MODFET) with 0.1 μm gate-length have been fabricated on a high hole mobility SiGe-Si heterojunction grown by ultrahigh vacuum chemical vapor deposition. The MODFET devices exhibited an extrinsic transconductance (g_m) of 142 mS/mm, a unity current gain cut-off frequency (f_T) of 45 GHz and a maximum oscillation frequency (f_MAX) of 81 GHz, 5 nm-thick high quality jet-vapor-deposited (JVD) SiO₂ was utilized as gate dielectric for the MOS-MODFET's. The devices exhibited a lower gate leakage current (1 nA/μm at V_gs=6 V) and a wider gate operating voltage swing in comparison to the MODFET's. However, due to the larger gate-to-channel distance and the existence of a parasitic surface channel, MOS-MODFET's demonstrated a smaller peak g _m of 90 mS/mm, f_T of 38 GHz, and f_max of 64 GHz. The threshold voltage shifted from 0.45 V for MODFET's to 1.33 V for MOS-MODFET's. A minimum noise figure (NF_min) of 1.29 dB and an associated power gain (G_a) of 12.8 dB were measured at 2 GHz for MODFET's, while the MOS-MODFET's exhibited a NF _min of 0.92 dB and a G_a of 12 dB at 2 GHz. These DC, RF, and high frequency noise characteristics make SiGe/Si MODFET's and MOS-MODFET's excellent candidates for wireless communications     

Demonstration of aluminum-free metamorphic InP/In0.53Ga0.47As/InP double heterojunction bipolar transistors on GaAssubstrates

We report, for the first time, the successful fabrication of aluminum-free metamorphic (MM) InP/In_0.53 Ga_0.47 As/InP double heterojunction bipolar transistors (DHBTs) on GaAs substrates with a linearly graded In_xGa_1-xP buffer grown by solid-source molecular beam epitaxy (SSMBE). Devices with 5×5 μm² emitters display a peak current gain of 40 and a common-emitter breakdown voltage (BV_CE0) higher than 9 V, a current gain cut-off frequency (f_T) of 48 GHz and a maximum oscillation frequency (f_max) of 42 GHz. A minimum noise figure of 2.9 dB and associated gain of 19.5 dB were measured at a collector current level of 2.6 mA at 2 GHz. Detailed analysis suggests that the degradation of the base-emitter heterojunction interface and the increase of bulk recombination are the most probable causes for the poorer device performance of current metamorphic HBTs compared with lattice-matched HBTs     

A 40-GHz D-type flip-flop using AlGaAs/GaAs HBT's

We report master-slave D-type flip-flop (D-FF) circuit implemented with AlGaAs/GaAs HBT's. The fabricated HBT's had an f_T of 107 GHz and an f_max of 110 GHz. To maximize the speed, the logic swing and transistor size in the IC were optimized. In the D-FF, to facilitate the high-speed testing, a selector circuit was integrated on the same chip. As a result, the operation of this IC was confirmed up to 40 GHz, which is the highest speed in D-FF     

Small-scaled InGaP/GaAs HBTs with WSi/Ti base electrode and buriedSiO2

This paper describes the fabrication and characteristics of small-scaled InGaP/GaAs HBTs with high-speed as well as low-current operation. To reduce both the emitter size S_E and the base-collector capacitance C_BC simultaneously, the HBTs are fabricated by using WSi/Ti as the base electrode and by burying SiO₂ in the extrinsic base-collector region under the base electrode. WSi/Ti simplifies and facilitates processing to fabricate a small base electrode, and makes it possible to reduce the width of the base contact to less than 0.4 μm without the large increase in the base resistance. The DC current gain of 20 is obtained for an HBT with S _E of 0.3×1.6 μm² due to the suppression of emitter size effect by using InGaP as the emitter material. An HBT with SE of 0.6×4.6 μm² exhibited f_T of 138 GHz and f_max of 275 GHz at I_C of 4 mA; and an HBT with SE of 0.3×1.6 μm² exhibited f_T of 96 GHz and f_max of 197 GHz at I_C of 1 mA. These results indicate the great potential of these HBTs for high-speed and low-power circuit applications     

Relation between low-frequency noise and long-term reliability ofsingle AlGaAs/GaAs power HBTs

Self-aligned AlGaAs/GaAs single heterojunction bipolar transistors (HBTs) were fabricated using an advanced processing technology for microwave and millimeter-wave power applications. These devices were processed simultaneously, on different epilayers with similar layer structure design supplied from different vendors. They showed similar dc characteristics (current gain, β=30) and their microwave performance was also identical (f_T=60 GHz, f_max=100 GHz). The HBTs showed different noise and reliability characteristics depending on their epilayer origin. HBT's from the high-reliability wafer showed MTTF of 10⁹ h at junction temperature of 120°C. They also presented very small 1/f noise with corner frequencies in the range of a few hundred Hz. Devices were subjected to bias and temperature stress for testing their noise and reliability characteristics. Stressed and unstressed devices showed generation-recombination noise with activation energies between 120-210 meV. Stress was found to increase the generation-recombination noise intensity but not its activation energy. These HBTs did not show any surface-related noise indicating that processing did not significantly influence noise characteristics. It was found that the base noise spectral density at low frequency can be correlated to the device long term reliability     

A design technique for a 60 GHz-bandwidth distributed basebandamplifier IC module

A DC-60 GHz, 9 dB distributed amplifier IC module is fabricated with 0.15 μm InAlAs-InGaAs low-noise HEMTs with 155 GHz f_T and 234 GHz f_max. The device is mounted in a metal package with 1.8 mm coaxial cable signal interfaces. The package is specially designed using three-dimensional electromagnetic field analyses, resulting in very flat frequency characteristics of the module within 1.5 dB gain ripples over the entire bandwidth. A multichip module loaded with two amplifier ICs in cascade is also fabricated, and operates at a 17.5 dB gain from 60 kHz to 48 GHz. The 1 dB gain compression output power is about 5 dBm for both modules. The noise figure of the single-chip module is approximately 4 dB over a 10-40 GHz frequency range     

High-speed small-scale InGaP/GaAs HBT technology and itsapplication to integrated circuits

We have developed the advanced performance, small-scale InGaP/GaAs heterojunction bipolar transistors (HBTs) by using WSi/Ti base electrode and buried SiO₂ in the extrinsic collector. The base-collector capacitance C_BC was further reduced to improve high-frequency performance. Improving the uniformity of the buried SiO ₂, reducing the area of the base electrode, and optimizing the width of the base-contact enabled us to reduce the parasitic capacitance in the buried SiO₂ region by 50% compared to our previous devices. The cutoff frequency f_T of 156 GHz and the maximum oscillation frequency f_max of 255 GHz were obtained at a collector current I_C of 3.5 mA for the HBT with an emitter size S_E of 0.5×4.5 μm², and f_T of 114 GHz and f_max of 230 GHz were obtained at I_C of 0.9 mA for the HBT with S_E of 0.25×1.5 μm². We have also fabricated digital and analog circuits using these HBTs. A 1/8 static frequency divider operated at a maximum toggle frequency of 39.5 GHz with a power consumption per flip-flop of 190 mW. A transimpedance amplifier provides a gain of 46.5 dB·Ω with a bandwidth of 41.6 GHz at a power consumption of 150 mW. These results indicate the great potential of our HBTs for high-speed, low-power circuit applications     

基于AlN/GaN异质结的Ka波段GaN低噪声放大器研制

报道了基于AlN/GaN异质结的Ka波段低噪声放大器的研制结果.在SiC衬底上生长AlN/GaN异质结材料结构,采用电子束直写工艺制备了栅长70 nm的"T"型栅结构.器件最大电流密度为1.50 A/mm,最大跨导为650 mS/mm,通过S参数测试外推特征频率和最大频率分别为105 GHz和235 GHz.基于70 ...     

Bandwidth Potential of Cascode HBT-Based TWAs as a Function of Transistor ${ f} _{max} /{ f} _{ T}$ Ratio

The bandwidth potential of cascode HBT-based broadband amplifiers following the traveling-wave amplifier (TWA) concept is studied. An approximate expression for the gain of the circuit is derived, which is based on the transistor small-signal model and the artificial transmission-line parameters. In this way, a relation between the HBT cutoff frequencies f_T and f_max and the 3-dB cutoff frequency f_c of the amplifier is obtained. This is very useful for assessing the gain-bandwidth potential of a given HBT technology for cascode-based TWAs. Applying these results, we study the potential of two technologies with different f_max / f_T ratios, an InP technology with f_max / f_T of 120 GHz/190 GHz, and a GaAs technology with f_max / f_T of 170 GHz/36 GHz. The higher influence of /max (compared to f_t) on f_c is quantitatively demonstrated. TWAs in both technologies were realized and measured, and good agreement between measurement and theory is obtained.     

Noise performance of low power 0.25 micron gate ion implantedD-mode GaAs MESFET for wireless applications

We report on the noise performance of low power 0.25 μm gate ion implanted D-mode GaAs MESFETs suitable for wireless personal communication applications. The 0.25 μm×200 μm D-mode MESFET has a f_t of 18 GHz and f_max of 33 GHz at a power level of 1 mW (power density of 5 mW/mm). The noise characteristics at 4 GHz for the D-mode MESFET are F_min=0.65 dB and G_assoc =13 dB at 1 mW. These results demonstrate that the GaAs D-mode MESFET is also an excellent choice for low power personal communication applications