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     

Submicron self-aligned HBT's by selective emitter regrowth

Fabrication of fully self-aligned heterojunction bipolar transistors (HBTs) by selective emitter regrowth is described. Scaled devices with emitter dimensions as small as 0.4×7 μm² demonstrate current gain up to 29, with successful suppression of surface recombination effects. The RF characteristics of a 1.4×11 μm² device exhibited f_T and f _MAX of 75 and 46 GHz, respectively, and is limited by the refractory base metallization. This technology is promising for scaled HBT applications where high-speed and low-power dissipation are critical     

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     

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     

Ultra-high-speed InP/InGaAs heterojunction bipolar transistors

We report on the microwave performance of InP/In_0.53Ga _0.47As heterojunction bipolar transistors (HBT's) utilizing a carbon-doped base grown by chemical beam epitaxy (CBE). The f_T and f_max of the HBT having two 1.5×10 μm² emitter fingers were 175 GHz and 70 GHz, respectively, at I_C=40 mA and V_CE=1.5 V. To our knowledge, the f _T of this device is the highest of any type of bipolar transistors yet reported. These results indicate the great potential of carbon-doped base InP/InGaAs HBT's for high-speed applications     

Integration of GalnP/GaAs heterojunction bipolar transistors andhigh electron mobility transistors

Integration of carbon-doped GaInP/GaAs heterojunction bipolar transistors (HBTs) and high electron mobility transistors (HEMTs) is demonstrated by growing an HBT on the top of a HEMT. A current gain of 60, a cutoff frequency of 59 GHz and a maximum oscillation frequency of 68 GHz were obtained for a 5×15 μm² self-aligned HBT. The HEMT, with a gate length of 1.5 μm has a transconductance of 210 mS/mm, a cutoff frequency of 9 GHz and a maximum oscillation frequency of 22 GHz. It is shown that the GaInP/GaAs HBT on the HEMT is a simple Bi-FET technology suitable for microwave and mixed signal applications     

A 5-GHz SiGe HBT return-to-zero comparator for RF A/D conversion

This paper presents a monolithic comparator implemented in a 0.5-μm SiGe heterojunction bipolar transistor (HBT) process. The SiGe HBT process provides HBT npn transistors with maximum f_T over 40 GHz and f_max over 55 GHz. The comparator circuit employs a resettable slave stage, which was designed to produce return-to-zero output data. Operation with sampling rates up to 5 GHz has been demonstrated by both simulation and experiments. The comparator chip attains an input range of 1.5 V, dissipates 89 mW from a 3-V supply, and occupies a die area of 407×143 μm². The comparator is intended for analog-to-digital (A/D) conversion of 900 MHz RF signals     

Self-aligned SiGe NPN transistors with 285 GHz f/sub MAX/ and 207 GHz f/sub T/ in a manufacturable technology

This paper reports on SiGe NPN HBTs with unity gain cutoff frequency (f_T) of 207 GHz and an f_MAX extrapolated from Mason's unilateral gain of 285 GHz. f_MAX extrapolated from maximum available gain is 194 GHz. Transistors sized 0.12×2.5 μm² have these characteristics at a linear current of 1.0 mA/μm (8.3 mA/μm²). Smaller transistors (0.12×0.5 μm²) have an f_T of 180 GHz at 800 μA current. The devices have a pinched base sheet resistance of 2.5 kΩ/sq. and an open-base breakdown voltage BV_CEO of 1.7 V. The improved performance is a result of a new self-aligned device structure that minimizes parasitic resistance and capacitance without affecting f_T at small lateral dimensions     

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     

Metamorphic InP/InGaAs heterojunction bipolar transistors on GaAssubstrate: DC and microwave performances

High-performance InP/In_0.53Ga_0.47As metamorphic heterojunction bipolar transistors (MHBTs) on GaAs substrate have been fabricated using In_xGa_1-xP strain relief buffer layer grown by solid-source molecular beam epitaxy (SSMBE). The MHBTs exhibited a dc current gain over 100, a unity current gain cutoff frequency (f_T) of 48 GHz and a maximum oscillation frequency (f_MAX) of 42 GHz with low junction leakage current and high breakdown voltages. It has also been shown that the MHBTs have achieved a minimum noise figure of 2 dB at 2 GHz (devices with 5×5 μm ² emitter) and a maximum output power of 18 dBm at 2.5 GHz (devices with 5×20 μm² emitter), which are comparable to the values reported on the lattice-matched HBTs (LHBTs). The dc and microwave characteristics show the great potential of the InP/InGaAs MHBTs on GaAs substrate for high-frequency and high-speed applications     

High-speed, low-noise InGaP/GaAs heterojunction bipolar transistors

We have demonstrated self-aligned InGaP/GaAs heterojunction bipolar transistors (HBT's) with excellent dc, microwave, and noise performance. A 3×10 μm² emitter finger device achieved a cutoff frequency of f_T=66 GHz and a maximum frequency of oscillation of f_max=109 GHz. A minimum noise figure of 1.12 dB and an associated gain of 11 dB were measured at 4 GHz. These results are the highest combined f_T+f_max and the lowest noise figure reported for an InGaP/GaAs HBT and are attributed to material quality and the use of self-aligned base contacts. These data clearly demonstrate the viability of InGaP/GaAs HBT's for high-speed, low-noise circuit applications     

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     

Application of selective epitaxial silicon and chemo-mechanicalpolishing to bipolar transistors

Successful demonstration of single-polysilicon bipolar transistors fabricated using selective epitaxial growth (SEG) and chemo-mechanical polishing (CMP) is reported. The pedestal structure made possible by the SEG/CMP process combination results in significantly reduced extrinsic-base collector capacitance. Cut-off frequency (f_T) of devices with emitter stripe width of 1 μm, a base width of 110 nm, and a peak base doping of 3×10¹⁸ cm^-3 have been observed to improve from 16 GHz to 22 GHz when the extrinsic-base collector overlap is decreased from 1 μm to 0.2 μm. Leakage current, often a problem for SEG structures, has been reduced to 27 nA/cm² for the area component, and 10 nA/cm for the edge component, by (1) appropriate post-polish processing, including a high-temperature anneal and sacrificial oxidation, (2) aligning the device sidewalls along the 〈100〉 direction, and (3) the presence of the pedestal structure. Base-emitter junction nonideality in these transistors has also been investigated     

SiGe pMODFETs on silicon-on-sapphire substrates with 116 GHzfmax

The dc and microwave results of Si_0.2Ge_0.8/Si_0.7Ge_0.3 pMODFETs grown on silicon-on-sapphire (SOS) substrates by ultrahigh vacuum chemical vapor deposition are reported. Devices with L_g=0.1 μm displayed high transconductance (377 mS/mm), low output conductance (25 mS/mm), and high gate-to-drain breakdown voltage (4 V). The dc current-voltage (I-V) characteristics were also nearly identical to those of control devices grown on bulk Si substrates. Microwave characterization of 0.1×50 μm² devices yielded unity current gain (f_T) and unilateral power gain (f _max) cutoff frequencies as high as 50 GHz and 116 GHz, respectively. Noise parameter characterization of 0.1×90 μm² devices revealed minimum noise figure (F_min) of 0.6 dB at 3 GHz and 2.5 dB at 20 GHz     

A novel monolithic HBT-p-i-n-HEMT integrated circuit with HBTactive feedback and p-i-n diode variable gain control

We report the world's first functional MMIC circuit integrating HBT's, HEMT's, and vertical p-i-n diodes on a single III-V substrate. The 1-10 GHz variable gain amplifier monolithically integrates HEMT, HBT, and vertical p-i-n diode devices has been fabricated using selective MBE and a merged processing technology. The VGA offers low-noise figure, wideband gain performance, and good gain flatness over a wide gain control range. A noise figure below 4 dB was achieved using a HEMT transistor for the amplifier stage and a wide bandwidth of 10 GHz. A nominal gain of 10 dB was achieved by incorporating HBT active feedback techniques and 12 dB of gain control range was obtained using a vertical p-i-n diode as a varistor, all integrated into a compact 1.5×0.76 mm² MMIC. The capability of monolithically integrating HBT's, HEMT's, and p-i-n's in a merged process will stimulate the development of new monolithic circuit techniques for achieving optimal performance as well as provide a foundation for high performance mixed-mode multifunctional MMIC chips     

Ultrahigh fT and fmax new self-alignmentInP/InGaAs HBT's with a highly Be-doped base layer grown by ALE/MOCVD

We report on a new self-alignment (SA) process and microwave performance of ALE/MOCVD grown InP/InGaAs heterojunction bipolar transistors (HBT's) with a base doping concentration of 1×10² 0 cm^-3. We obtained f_T of 161 GHz and f_max of 167 GHz with a 2×10 μm emitter. These high values indicate the best performance of InP/InGaAs HBT's ever reported, in so far as we know. These values were attained by reducing the base resistance using ALE/MOCVD and base-collector capacitance using a new SA process. These results indicate the great potential of these devices for ultrahigh-speed application     

High-performance, graded-base AlGaAs/InGaAs collector-upheterojunction bipolar transistors using a novel selective area regrowthprocess

Graded-base AlGaAs/InGaAs collector-up heterojunction bipolar transistors (C-up HBTs) were successfully fabricated using a novel selective area regrowth process to reduce the base resistance and their dc and microwave performances were evaluated. The base is compositionally graded to provide a quasi-built-in field which decreases the base transit time for high-frequency response and increases the base transport factor at low-temperature operation. A unity-gain cutoff frequency f_T=55 GHz and a maximum frequency of oscillation f _MAX=74 GHz for the C-up n-p-n HBT, and an f_T=48 GHz and an f_MAX= 39 GHz for the C-up p-n-p HBT were obtained for devices with a 5-μm×10-μm collector area. The nonself-aligned C-up HBT's reported here show great promise for future high-speed C-up complementary bipolar IC's     

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     

7.1 GHz bandwidth monolithically integratedIn0.53Ga0.47As/In0.52Al0.48As PIN-HBT transimpedance photoreceiver

A monolithically integrated photoreceiver using an InAlAs/InGaAs HBT-based transimpedance amplifier has been fabricated and characterized. The p-i-n photodiode is implemented using the base-collector junction of the HBT. The 5 μm×5 μm emitter area transistors have self-aligned base metal and non-alloyed Ti/Pt/Au contacts. Discrete transistors demonstrated f_T and f_max of 54 GHz and 51 GHz, respectively. The amplifier demonstrated a -3 dB transimpedance bandwidth of 10 GHz and a gain of 40 dBΩ. The integrated photoreceiver with a 10 μm×10 μm p-i-n photodiode showed a -3 dB bandwidth of 7.1 GHz     

Low temperature microwave characteristics of 0.1 μm gate-lengthpseudomorphicIn0.52Al0.48As/InxGa1-xAs(x=0.85 and 0.95) MODFET's

We have studied the microwave characteristics of 0.1 μm gate-length pseudomorphic In_0.52Al_0.48As/In_x Ga_1-xAs (x=0.85 and 0.95) modulation-doped field-effect transistors (MODFET's) at 300 K and lower temperatures down to 77 K. A maximum f_T of 151 GHz has been measured for a 0.1×55 μm² gate In_0.52Al_0.48As/In_0.85 Ga_0.15As MODFET at 77 K and this represents an improvement of 33% over the room temperature value. This behavior has been analyzed