Breakdown Enhancement of AlGaN/GaN HEMTs on 4-in Silicon by Improving the GaN Quality on Thick Buffer Layers

We have achieved a 9- $muhbox{m}$-thick AlGaN/GaN high-electron mobility transistor (HEMT) epilayer on silicon using thick buffer layers with reduced dislocation density $(D_{D})$. The crack-free 9- $muhbox{m}$-thick epilayer included 2- $muhbox{m}$ i-GaN and 7- $ muhbox{m}$ buffer. The HEMTs fabricated on these devices showed a maximum drain–current density of 625 mA/mm, transconductance of 190 mS/mm, and a high three-terminal OFF breakdown of 403 V for device dimensions of $L_{g}/W_{g}/L_{rm gd} = hbox{1.5/15/3} muhbox{m}$ . Without using a gate field plate, this is the highest $BV$ reported on an AlGaN/GaN HEMT on silicon for a short $L_{rm gd}$ of 3 $muhbox{m}$. A very high $BV$ of 1813 V across 10- $mu hbox{m}$ ohmic gap was achieved for i-GaN grown on thick buffers. As the thickness of buffer layers increased, the decreased $D_{D}$ of GaN and increased resistance between surface electrode and substrate yielded a high breakdown.      

14-GHz GaNAsSb Unitraveling-Carrier 1.3-$muhbox{m}$ Photodetectors Grown by RF Plasma-Assisted Nitrogen Molecular Beam Epitaxy

We report on picosecond pulsed response and 3-dB cutoff frequency of 1.3-$ muhbox{m}$ GaNAsSb unitraveling-carrier photodetectors (PDs) grown by molecular beam epitaxy using a radio-frequency plasma-assisted nitrogen source. The 0.1-$muhbox{m}$ -thick GaNAsSb photoabsorption layer contains 3.5% of N and 9% of Sb, resulting in a bandgap of 0.88 eV. The dark current densities at 0 and $-$9 V are 6 and 34 $hbox{mA}/hbox{cm}^{2}$, respectively. The GaNAsSb UTC PDs exhibit a temporal response width of 46 ps and a record 3-dB cutoff frequency of 14 GHz at $-$9 V.      

High-Performance 0.1-$muhbox{m}$ Gate AlGaN/GaN HEMTs on Silicon With Low-Noise Figure at 20 GHz

The realization of high-performance 0.1-$muhbox{m}$ gate AlGaN/GaN high-electron mobility transistors (HEMTs) grown on high-resistivity silicon substrates is reported. Our devices feature cutoff frequencies as high as $f_{T} = hbox{75} hbox{GHz}$ and $f_{rm MAX} = hbox{125} hbox{GHz}$, the highest values reported so far for AlGaN/GaN HEMTs on silicon. The microwave noise performance is competitive with results achieved on other substrate types, such as sapphire and silicon carbide, with a noise figure $F = hbox{1.2}{-}hbox{1.3} hbox{dB}$ and an associated gain $G_{rm ass} = hbox{8.0}{-}hbox{9.5} hbox{dB}$ at 20 GHz. This performance demonstrates that GaN-on-silicon technology is a viable alternative for low-cost millimeter-wave applications.      

High-Frequency ZnO Thin-Film Transistors on Si Substrates

Record microwave frequency performance was achieved with nanocrystalline ZnO thin-film transistors fabricated on Si substrates. Devices with 1.2-$muhbox{m}$ gate lengths and Au-based gate metals had current and power gain cutoff frequencies of $f_{T} = hbox{2.45} hbox{GHz}$ and $f_{max} = hbox{7.45} hbox{GHz}$ , respectively. Same devices had drain–current on/off ratios of $hbox{5} times hbox{10}^{10}$, exhibited no hysteresis effects and could be operated at a current density of 348 mA/mm. The microwave performances of devices with 1.2- and 2.1- $muhbox{m}$ gate lengths and 50- and 100-$muhbox{m}$ gate widths were compared.      

High Microwave-Noise Performance of AlGaN/GaN MISHEMTs on Silicon With Gate Insulator Grown by ALD

High microwave-noise performance is realized in AlGaN/GaN metal–insulator semiconductor high-electron mobility transistors (MISHEMTs) on high-resistivity silicon substrate using atomic-layer-deposited (ALD) $hbox{Al}_{2}hbox{O}_{3}$ as gate insulator. The ALD $hbox{Al}_{2}hbox{O}_{3}/hbox{AlGaN/GaN}$ MISHEMT with a 0.25- $muhbox{m}$ gate length shows excellent microwave small signal and noise performance. A high current-gain cutoff frequency $f_{T}$ of 40 GHz and maximum oscillation frequency $f_{max}$ of 76 GHz were achieved. At 10 GHz, the device exhibits low minimum-noise figure $(hbox{NF}_{min})$ of 1.0 dB together with high associate gain $(G_{a})$ of 10.5 dB and low equivalent noise resistance $(R_{n})$ of 29.2 $Omega$. This is believed to be the first report of a 0.25-$muhbox{m}$ gate-length GaN MISHEMT on silicon with such microwave-noise performance. These results indicate that the AlGaN/GaN MISHEMT with ALD $hbox{Al}_{2}hbox{O}_{3}$ gate insulator on high-resistivity Si substrate is suitable for microwave low-noise applications.      

Enhanced Electrical and Thermal Properties of Trench Metal–Oxide–Semiconductor Field-Effect Transistor Built on Copper Substrate

Vertical metal–oxide–semiconductor field-effect transistors (UMOSFETs) were built on silicon substrates thinned to 7 $muhbox{m}$ and plated with 50- $muhbox{m}$ copper as drain electrode and mechanical support. Compared to the same devices on silicon substrates of 200 $muhbox{m}$ thick, the UMOSFET on 7-$muhbox{m}$ silicon demonstrates at least 16% less channel resistance and two times better device ruggedness. The reduced resistance is due to enhanced carrier mobility caused by increasing biaxial compressive thermal stress in silicon perpendicular to the channel, which is confirmed by a 3-D piezoresistance model. The doubling of ruggedness is attributed to a much improved transient thermal conductance.      

Transfer of GaN-Based Light-Emitting Diodes From Silicon Growth Substrate to Copper

III-nitride light-emitting diodes (LEDs) grown on Si (111) substrates have the potential of low-cost manufacturing for solid-state lighting and display, by taking advantage of the well-developed IC technologies of silicon. In this letter, LEDs grown on silicon substrates were transferred onto copper substrates, to maximize light extraction and heat dissipation. On Si substrates, $hbox{300} times hbox{300} muhbox{m}^{2}$ multiple quantum well InGaN LEDs were first grown and processed. The top surface of the fabricated devices was then temporarily bonded to a sapphire wafer and the Si substrate was chemically etched. Ti/Al/Ti/Au layers were deposited on the backside of LEDs. An 80-$muhbox{m}$ -thick copper layer was electroplated and the temporary bonding was removed, resulting in LEDs on copper substrate. The optical output power of LEDs on copper increased by $sim$ 70% as compared to that of the LEDs on silicon. The improved performance was attributed to the removal of the light-absorbing Si substrate and the good thermal conductivity of copper.      

Abrupt Delta-Doped InP/GaInAs/InP DHBTs With 0.45-$muhbox{m}$ -Wide T-Shaped Emitter Contacts

An abrupt pulse-doped InP/GaInAs/InP double heterojunction bipolar transistor having a 0.45- $muhbox{m}$-wide T-shaped emitter metal is reported. These two promising technologies for sub-100-nm emitters were previously demonstrated only for 1- $muhbox{m}$ emitters. The device exhibited typical dc and microwave performance to 0.5- $muhbox{m}$ emitter devices.      

Effective Crosstalk Isolation With Post-CMOS Selectively Grown Porous Silicon Technique for Radio Frequency System-on-Chip (SOC) Applications

In this letter, post-CMOS substrate selective-transformation engineering based on the selectively grown porous silicon (SGPS) technique is demonstrated to effectively suppress substrate crosstalk. The testing structures for crosstalk isolation are fabricated in a standard 0.18-$muhbox{m}$ CMOS process, and porous silicon trenches are selectively grown after processing from the backside of the silicon wafer. For a testing structure with 250-$muhbox{m}$ separation on Si, a 42.8-dB improvement (from $-$23.5 to $-$66.3 dB) for crosstalk isolation is achieved at 2 GHz. The characteristics of the SGPS substrate have been extracted using the conventional lump element model, which shows that our SGPS technique increases the substrate impedance by one order of magnitude. These results demonstrate that our post-CMOS substrate selective-transformation engineering is very promising for radio frequency system-on-chip applications.      

RF Performance of N-Polar AlGaN/GaN MIS-HEMTs Grown by MOCVD on Sapphire Substrate

We present a high-performance nitrogen-polar AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistor grown on sapphire substrate using metal–organic chemical vapor deposition. Source-terminated field plates were used to mitigate the electric field in the drain-extension region and reduce dc-to-RF dispersion. Devices with 0.7-$muhbox{m}$ gate length showed a current-gain cutoff frequency $(f_{T})$ of 14 GHz and a power-gain cutoff frequency $(f_{max})$ of 36 GHz. A continuous-wave output power density of 4.7 W/mm was measured at 4 GHz, with an associated power-added efficiency of 64% and a large-signal gain of 14.4 dB at a drain bias of 30 V.      

CMOS Avalanche Photodiode Embedded in a Phase-Shift Laser Rangefinder

This paper presents the design and the characterization of a CMOS avalanche photodiode (APD) working as an optoelectronic mixer. The $hbox{P}^{+}hbox{N}$ photodiode has been implemented in a commercial 0.35-$muhbox{m}$ CMOS technology after optimization with SILVACO. The surface of the active region is $ hbox{3.78} cdot hbox{10}^{-3} hbox{cm}^{2}$. An efficient guard-ring structure has been created using the lateral diffusion of two n-well regions separated by a gap of 1.2 $mu hbox{m}$. When biased at $-$2 V, the best responsitivity $S_{lambda ,{rm APD}} = hbox{0.11} hbox{A/W}$ is obtained at $lambda = hbox{500} hbox{nm}$. This value can easily be improved by using an antireflection coating. At $lambda = hbox{472} hbox{nm}$, the internal gain is about 75 at $-$6 V and 157 at $-$7 V. When biased at $-$6 V, the APD achieves a dark current of 128 $muhbox{A} cdot hbox{mm}^{-2}$ and an excess noise factor $F = hbox{20}$ . Then, the APD is successfully used as an optoelectronic mixer to improve the signal-to-noise ratio of a low-voltage embedded phase-shift laser rangefinder.      

A CMOS Ultra Low-Power and Highly Efficient UWB-IR Transmitter for WPAN Applications

This brief presents an on–off $LC$ oscillator-based ultrawideband impulse radio (UWB-IR) transmitter for long-range application. A thorough theoretical analysis of the pulse generation is provided. Implemented in a 0.18-$muhbox{m}$ CMOS, the transmitter works in the UWB lower band of 3–5 GHz and consumes an ultralow average power of 236 $muhbox{W}$ at 1.8-V power supply. UWB pulses with a bandwidth of 2 GHz and 10-dB sidelobe suppression are generated. The transmitter can deliver a large differential output swing of 4.9 V under 100-$Omega$ load with the highest power efficiency of 25.4% to date. It is targeted for wireless sensor network (WSNs) and wireless personal area network (WPAN) applications.      

High-Performance N-Face GaN Microwave MIS-HEMTs With > 70% Power-Added Efficiency

A high-performance N-face GaN metal–insulator–semiconductor high-electron-mobility transistor was fabricated. A dual-AlN back-barrier scheme was developed using polarization engineering to provide a large total dipole moment, which allowed enhanced modulation doping for a higher 2-D electron gas density without parallel conduction. Devices with 0.6-$muhbox{m}$ gate length showed an $f_{T}$ and $f_{max}$ of 17 and 58 GHz, respectively. A highest power-added efficiency (PAE) of 71% at 4 GHz was measured in these devices with 20-V drain bias. At 28 V, an output power density of 6.4 W/mm with 67% PAE was achieved.      

Improvement in the Light Output Power of GaN-Based Light-Emitting Diodes by Natural-Cluster Silicon Dioxide Nanoparticles as the Current-Blocking Layer

In this study, the fabrication and characterization of InGaN–GaN multiple-quantum-well light-emitting diodes (LEDs) with silicon dioxide ($hbox{SiO}_{2}$) nanoparticles as the current-blocking layer (CBL) are described. The performance was improved by introducing $hbox{SiO}_{2}$ nanoparticles, not deposited by commonly used plasma-enhanced chemical vapor deposition, as the CBL beneath the p-pad. The injected current was forced to spread outside instead of flowing directly downward. At 20 mA, the light output power of the LED with a CBL was increased 15.7% as compared to that of the conventional LED. The forward voltage of the LED with the $hbox{SiO}_{2}$ nanoparticle CBL was 3.34 V at 20 mA, which was slightly higher than that of the conventional LED (3.29 V). The increase in the light output power can be attributed to the injection of additional current into the light-emitting active layer of the LED by the $hbox{SiO}_{2}$ nanoparticles CBL and thus a reduction in optical absorption at the p-pad.      

A Fully Differential Comparator-Based Switched-Capacitor $DeltaSigma$ Modulator

In this brief, a fully differential comparator-based switched-capacitor (CBSC) second-order delta-sigma $(DeltaSigma)$ modulator is presented. To ensure differential operation, the CBSC $DeltaSigma$ modulator utilizes a common-mode feedback circuit to balance the pull-up current and the pull-down current in the ramp generator. This modulator has been fabricated in a standard 0.18-$muhbox{m}$ CMOS process. The active area is 0.21 $hbox{mm}^{2}$, and the power consumption, excluding output buffers, is 0.42 mW from a 1.8-V supply. This modulator achieves 65.3-dB signal-to-noise-plus-distortion ratio and an input dynamic range of 71 dB when sampled at 2.56 MS/s $(hbox{OSR} = 64)$.      

A 0.6-V Delta–Sigma Modulator With Subthreshold-Leakage Suppression Switches

A 0.6-V 34-$muhbox{W}$ delta–sigma modulator implemented by using a standard 0.13-$muhbox{m}$ complementary metal–oxide–semiconductor technology is presented. This brief analyzes a subthreshold-leakage current problem in switched-capacitor circuits and proposes subthreshold-leakage suppression switches to solve the problem. To verify the operation of the subthreshold-leakage suppression switches, two different fifth-order delta–sigma modulators are implemented with conventional switches and new switches. The input feedforward architecture is used to reduce the voltage swings of the integrators. A high-performance low-quiescent amplifier architecture is developed for the modulator. The modulator, with new switches, achieves a dynamic range of 83 dB, a peak signal-to-noise ratio of 82 dB, and a peak signal-to-noise-plus-distortion ratio of 81 dB in a signal bandwidth of 20 kHz. The power consumption is 34 $muhbox{W}$ for the modulator, and the core chip size is 0.33 $hbox{mm}^{2}$ .      

Temperature Characteristics of Gain Profiles in 1.3-$ muhbox{m} p$-Doped and Undoped InAs/GaAs Quantum-Dot Lasers

The modal gain and differential gain of 1.3-$muhbox{m}break p$ -doped and undoped InAs/GaAs quantum-dot (QD) lasers have been investigated as a function of injection current under different operation temperatures. The results show that $p$ -doping improves the modal and differential gains in QD lasers at high temperatures. Exponential decrease in the differential gain profiles were observed in both types of lasers from 20 $^{circ}hbox{C}$ to 80 $^{circ}hbox{C}$. Theoretical calculations based on the rate equation model for the undoped QD laser gain at different temperatures are presented.      

Microwave ZnO Thin-Film Transistors

We have developed ZnO thin-film transistor design and fabrication techniques to demonstrate microwave frequency operation with 2-$muhbox{m}$ gate length devices produced on GaAs substrates. Using $hbox{SiO}_{2}$ gate insulator and pulsed laser deposited ZnO active layers, a drain–current on/off ratio of $hbox{10}^{12}$, a drain–current density of 400 mA/mm, a field-effect mobility of $hbox{110} hbox{cm}^{2}!/ hbox{V}!cdothbox{s}$, and a subthreshold gate voltage swing of 109 mV/dec were achieved. Devices with Ti-gate metal had current and power gain cutoff frequencies of 500 and 400 MHz, respectively.      

Low On-Resistance High-Breakdown Normally Off AlN/GaN/AlGaN DHFET on Si Substrate

Ultrathin-barrier normally off AlN/GaN/AlGaN double-heterostructure field-effect transistors using an in situ SiN cap layer have been fabricated on 100-mm Si substrates for the first time. The high 2DEG density in combination with an extremely thin barrier layer leads to enhancement-mode devices with state-of-the-art combination of specific on-resistance that is as low as 1.25 $hbox{m}Omegacdothbox{cm}^{2}$ and breakdown voltage of 580 V at ${V}_{rm GS} = hbox{0} hbox{V}$ . Despite the 2-$muhbox{m}$ gate length used, the transconductance peaks above 300 mS/mm. Furthermore, pulsed measurements show that the devices are dispersion free up to high drain voltage ${V}_{rm DS} = hbox{50} hbox{V}$. More than 200 devices have been characterized in order to confirm the reproducibility of the results.      

Improved Stress Reliability of Analog Metal–Insulator–Metal Capacitors Using $hbox{TiO}_{2}/hbox{ZrO}_{2}$ Dielectrics

We have studied the stress reliability of high-$kappa$ $hbox{Ni/TiO}_{2}/hbox{ZrO}_{2}/hbox{TiN}$ metal–insulator–metal capacitors under constant-voltage stress. The increasing $hbox{TiO}_{2}$ thickness on $hbox{ZrO}_{2}$ improves the 125-$^{circ}hbox{C}$ leakage current, capacitance variation $(Delta C/C)$, and long-term reliability. For a high density of 26 $hbox{fF}/mu hbox{m}^{2}$ , good extrapolated ten-year reliability of small $Delta C/ break C sim hbox{0.71}%$ is obtained for the $ hbox{Ni/10-nm-}hbox{TiO}_{2}/hbox{6.5-nm-} hbox{ZrO}_{2}/break hbox{TiN}$ device at 2.5-V operation.