Enhancement-mode power heterojunction FET utilizingAl0.5Ga0.5As barrier layer with negligibleoperation gate current for digital cellular phones

We have developed a novel enhancement-mode double-doped AlGaAs/InGaAs/AlGaAs heterojunction FET (HJFET) with a 5 nm thick Al_0.5Ga_0.5As barrier layer inserted between an In _0.2Ga_0.8As channel layer and an upper Al_0.2 Ga_0.8As electron supply layer. The Al_0.5Ga _0.5As barrier layer reduces gate current under high forward gate bias voltage, resulting in a high forward gate turn-on voltage (V _F) of 0.87 V, which is 170 mV higher than that of an HJFET without the barrier layer. Suppression of gate current assisted by a parallel conduction path in the upper electron supply layer was found to be also important for achieving the high V_F. The developed device exhibited a high maximum drain current of 300 mA/mm with a threshold voltage of 0.17 V. A 950 MHz PDC power performance was evaluated under single 3.5 V operation. An HJFET with a 0.5 μm long gate exhibited 0.92 W output power and 63.6% power-added efficiency with 0.08 mA gate current (I_g) at -48 dBc adjacent channel leakage power at 50 kHz off-center frequency. This I_g is one-thirteenth to that of the HJFET without the barrier layer. These results indicate that the developed enhancement-mode HJFET is suitable for single low voltage operation power applications     

Two-dimensional metal-semiconductor field effect transistor forultra low power circuit applications

We describe a novel 2-dimensional metal-semiconductor field effect transistor (2-D MESFET) in which opposing Schottky side gates formed on the sidewall of a modulation-doped AlGaAs-InGaAs heterostructure modulate the channel width and the drain current. The drain current ranged from 0 to 210 μA and the maximum measured transconductance was 212 μS (212 mS/mm) at room temperature for a 1×1 micron channel. The threshold voltage was -0.45 V and the subthreshold ideality factor was 1.30. The estimated gate capacitance was 0.8 fF/μm, or about half the equivalent capacitance of conventional HFET's. The cutoff frequency f_T was estimated to be 21 GHz. The narrow channel effect, which limits the minimum power consumption in conventional FET's, is practically eliminated in this device     

Step-like heterostructure barrier varactor

Conduction mechanisms in step-like heterostructure barrier varactor (HBV) have been investigated by means of measurements of current- and capacitance-voltage (C-V) characteristics. For this purpose, In_0.53Ga_0.47As/In_0.52Al_0.48 As/AlAs single barrier varactors have been fabricated and characterized from room temperature up to ~400 K. The devices exhibit state-of-the art results with a breakdown voltage (V_b) of ~6 V for a leakage current of 10 A/cm², a C-V ratio of 5:1 and a 0 V capacitance of 2 fF/μm². By solving the Poisson equation in the Thomas-Fermi approach and the Schrodinger equation, it is shown that the leakage current mechanisms are dominated by a resonant tunneling contribution below the voltage threshold. Subsequently, the results are interpreted in terms of an apparent barrier height equal to 600 meV near equilibrium. Above threshold, we attribute the drastic increase in the current-voltage relationship to impact ionization     

Low-threshold current low-voltage vertical-cavity surface-emittinglasers with low-Al-content p-type mirrors grown by MOCVD

InGaAs quantum-well vertical-cavity surface-emitting lasers with low-Al-content p-type mirrors grown by metalorganic chemical vapor deposition (MOCVD) have have been characterized. Series resistance in p-type Al_xGa_1-xAs/GaAs mirrors decreases drastically as the Al content in Al_xGa_1-xAs decreases from AlAs. Air-post devices with a p-type Al_0.06Ga _0.4As/GaAs top mirror exhibit a room temperature CW threshold current of 1.8 mA at an operating voltage of 2.0 V (with a threshold power consumption at 3.6 mW)     

4H-SiC MESFET的特性研究

对4H-SiC MESFET的特性研究发现,在室温下4H-SiC MESFET饱和漏电流的值为0.75A/mm,随着温度的上升,器件的饱和漏电流和跨导一直下降;栅长越短,沟道层掺杂浓度越高,饱和漏电流就越大.300K时器件的击穿电压为209V,计算出来的最大功率密度可达19.22W/mm.这些结果显示了4H-SiC在高温、高压、大功率器件应用中的优势.     

Electrical characteristics of an optically controlled N-channelAlGaAs/GaAs/InGaAs pseudomorphic HEMT

Electrical characteristics of an n-channel Al_0.3Ga_0.7As/GaAs/In_0.13Ga_0.87 As pseudomorphic HEMT (PHEMT) with L_g=1 μm on GaAs are characterized under optical input (P_opt). Gate leakage and drain current have been analyzed as a function of V_GS, V _DS, and P_opt. We observed monotonically increasing gate leakage current due to the energy barrier lowering by the optically induced photovoltage, which means that gate input characteristics are significantly limited by the photovoltaic effect. However, we obtained a strong nonlinear photoresponsivity of the drain current, which is limited by the photoconductive effect. We also proposed a device model with an optically induced parasitic Al_0.3Ga_0.7As MESFET parallel to the In_0.13Ga_0.87As channel PHEMT for the physical mechanism in the drain current saturation under high optical input power     

InP-based enhancement-mode pseudomorphic HEMT with strainedIn0.45Al0.55As barrier andIn0.75Ga0.25As channel layers

Using strained aluminum-rich In_0.45Al_0.55As as Schottky contact materials to enhance the barrier height and indium-rich In_0.75Ga_0.25As as channel material to enhance the channel performance, we have developed InP-based enhancement-mode pseudomorphic InAlAs/InGaAs high electron mobility transistors (E-PHEMT's) with threshold voltage of about 170 mv. A maximum extrinsic transconductance of 675 mS/mm and output conductance of 15 mS/mm are measured respectively at room temperature for 1 μm-gate-length devices, with an associated maximum drain current density of 420 mA/mm at gate voltage of 0.9 V. The devices also show excellent rf performance with cutoff frequency of 55 GHz and maximum oscillation frequency of 62 GHz. To the best of the authors' knowledge, this is the first time that InP-based E-PHEMT's with strained InAlAs barrier layer have been demonstrated     

High-Performance Inversion-Type Enhancement-Mode InGaAs MOSFET With Maximum Drain Current Exceeding 1 A/mm

High-performance inversion-type enhancement- mode (E-mode) n-channel In_0.65Ga_0.35As MOSFETs with atomic-layer-deposited Al₂O₃ as gate dielectric are demonstrated. A 0.4-mum gate-length MOSFET with an Al₂O₃ gate oxide thickness of 10 nm shows a gate leakage current that is less than 5 times 10^-6 A/cm² at 4.0-V gate bias, a threshold voltage of 0.4 V, a maximum drain current of 1.05 A/mm, and a transconductance of 350 mS/mm at drain voltage of 2.0 V. The maximum drain current and transconductance scale linearly from 40 mum to 0.7 mum. The peak effective mobility is ~1550 cm²/V ldr s at 0.3 MV/cm and decreases to ~650 cm²/V ldr s at 0.9 MV/cm. The obtained maximum drain current and transconductance are all record-high values in 40 years of E-mode III-V MOSFET research.     

Fabrication of room temperature continuous-wave operation GaN-based ultraviolet laser diodes

Two kinds of continuous-wave GaN-based ultraviolet laser diodes (LDs) operated at room temperature and with different emission wavelengths are demonstrated.The LDs epitaxial layers are grown on GaN substrate by metalorganic chemical vapor deposition,with a 10×600 μm2 ridge waveguide structure.The electrical and optical characteristics of the ultraviolet LDs are investigated under direct-current injection at room temperature. The stimulated emission peak wavelength of first LD is 392.9 nm,the threshold current density and voltage is 1.5 kA/cm² and 5.0 V,respectively.The output light power is 80 mW under the 4.0 kA/cm² injection current density. The stimulated emission peak wavelength of second LD is 381.9 nm,the threshold current density the voltage is 2.8 kA/cm² and 5.5 V,respectively.The output light power is 14 mW under a 4.0 kA/cm² injection current density.     

Ga0.51In0.49P/In0.15Ga0.85As/GaAs pseudomorphic doped-channel FET with high-current densityand high-breakdown voltage

Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs pseudomorphic doped-channel FETs exhibiting excellent DC and microwave characteristics were successfully fabricated. A high peak transconductance of 350 mS/mm, a high gate-drain breakdown voltage of 31 V and a high maximum current density (575 mA/mm) were achieved. These results demonstrate that high transconductance and high breakdown voltage could be attained by using In_0.15Ga_0.85As and Ga_0.51In_0.49P as the channel and insulator materials, respectively. We also measured a high-current gain cut-off frequency f_t of 23.3 GHz and a high maximum oscillation frequency f_max of 50.8 GHz for a 1-μm gate length device at 300 K. RF values where higher than those of other works of InGaAs channel pseudomorphic doped-channel FETs (DCFETs), high electron mobility transistors (HEMTs), and heterostructure FETs (HFETs) with the same gate length and were mainly attributed to higher transconductance due to higher mobility, while the DC values were comparable with the other works. The above results suggested that Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs doped channel FET's were were very suitable for microwave high power device application     

High performance 0.35 μm gate-length monolithicenhancement/depletion-mode metamorphicIn0.52Al0.48As/In0.53Ga0.47As HEMTs on GaAs substrates

Monolithic integration of enhancement (E)- and depletion (D)-mode metamorphic In_0.52Al_0.48As/In_0.53Ga_0.47 As/GaAs HEMTs with 0.35 μm gate-length is presented for the first time. Epilayers are grown on 3-inch SI GaAs substrates using molecular beam epitaxy. A mobility of 9550 cm²/V-s and a sheet density of 1.12×10^{12 -2} are achieved at room temperature. Buried Pt-gate was employed for E-mode devices to achieve a positive shift in the threshold voltage. Excellent characteristics are achieved with threshold voltage, maximum drain current, and extrinsic transconductance of 100 mV, 370 mA/mm and 660 mS/mm, respectively for E-mode devices, and -550 mV, 390 mA/mm and 510 mS/mm, respectively for D-mode devices. The unity current gain cutoff frequencies of 75 GHz for E-mode and 80 GHz for D-mode are reported     

Narrow channel 2-D MESFET for low power electronics

A 2-D MESFET utilizing sidewall Schottky contacts on either side of a very narrow 2-d electron gas channel is described. Record transconductance of 295 and 130 mS/mm have been achieved at room temperature in 1.0 and 0.5 micron wide devices, respectively. We also present accurate 2-D MESFET current-voltage and capacitance-voltage models. These models have been implemented into AIM-Spice which was used to simulate DCFL inverter and ring oscillator circuits. The ring oscillator simulations predict a power-delay product of less than 0.1 fJ/gate at room temperature, suggesting that the 2-D MESFET may be useful for ultra low power electronics applications     

$hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ Channel MOSFETs With Self-Aligned InAs Source/Drain Formed by MEE Regrowth

Abstract-We report Al₂O₃Zln_0.53Ga_0.47As MOSFETs having both self-aligned in situ Mo source/drain ohmic contacts and self-aligned InAs source/drain n⁺ regions formed by MBE regrowth. The device epitaxial dimensions are small, as is required for 22-nm gate length MOSFETs; a 5-nm In_0.53Ga_0.47As channel with an In_0.4sAl_0.52As back confinement layer and the n⁺⁺ source/drain junctions do not extend below the 5-nm channel. A device with 200-nm gate length showed I_D = 0.95 mA/mum current density at V_GS = 4.0 V and g_m = 0.45 mS/mum peak transconductance at V_DS = 2.0 V.     

Digital CMOS IC's in 6H-SiC operating on a 5-V power supply

A CMOS technology in 6H-SiC utilizing an implanted p-well process is developed. The p-wells are fabricated by implanting boron ions into an n-type epilayer. PMOS devices are fabricated on an n-type epilayer while the NMOS devices are fabricated on implanted p-wells using a thermally grown gate oxide. The resulting NMOS devices have a threshold voltage of 3.3 V while the PMOS devices have a threshold voltage of -4.2 V at room temperature. The effective channel mobility is around 20 cm ²/Vs for the NMOS devices and around 7.5 cm²/Vs for the PMOS devices. Several digital circuits, such as inverters, NAND's, NOR's, and 11-stage ring oscillators are fabricated using these devices and exhibited stable operation at temperatures ranging from room temperature to 300°C. These digital circuits are the first CMOS circuits in 6H-SiC to operate with a 5-V power supply for temperatures ranging from room temperature up to 300°C     

Characteristics of a photonic bandgap single defect microcavityelectroluminescent device

A microcavity surface-emitting coherent electroluminescent device operating at room temperature under pulsed current injection is described. The microcavity is formed by a single defect in the center of a 2-D photonic crystal consisting of a GaAs-based heterostructure. The gain region consists of two 70-Å compressively strained In_0.15Ga_0.85As quantum wells, which exhibit a spontaneous emission peak at 940 nm. The maximum measured output power from a single device is 14.4 μW. The near-field image of the output resembles the calculated TE mode distribution in a single defect microcavity. The measured far-field pattern indicates the predicted directionality of a microcavity light source. The light-current characteristics of the device exhibit a gradual turn-on, or a soft threshold, typical of single- or few-mode microcavity devices. Analysis of the characteristics with the carrier and photon rate equations yields a spontaneous emission factor β≈0.06     

Submicrometer Inversion-Type Enhancement-Mode InGaAs MOSFET With Atomic-Layer-Deposited Al2O3 as Gate Dielectric

High-performance inversion-type enhancement-mode n-channel In_0.53Ga_0.47As MOSFETs with atomic-layer-deposited (ALD) Al₂O₃ as gate dielectric are demonstrated. The ALD process on III-V compound semiconductors enables the formation of high-quality gate oxides and unpinning of Fermi level on compound semiconductors in general. A 0.5-mum gate-length MOSFET with an Al₂O₃ gate oxide thickness of 8 nm shows a gate leakage current less than 10^-4 A/cm² at 3-V gate bias, a threshold voltage of 0.25 V, a maximum drain current of 367 mA/mm, and a transconductance of 130 mS/mm at drain voltage of 2 V. The midgap interface trap density of regrown Al₂O₃ on In_0.53Ga_0.47As is ~1.4 x 10¹²/cm² ldr eV which is determined by low-and high-frequency capacitance-voltage method. The peak effective mobility is ~1100 cm² / V ldr s from dc measurement, ~2200 cm²/ V ldr s after interface trap correction, and with about a factor of two to three higher than Si universal mobility in the range of 0.5-1.0-MV/cm effective electric field.     

Room temperature far infrared (8~10 μm) photodetectors usingself-assembled InAs quantum dots with high detectivity

Room temperature operation of far-infrared detectors made of self-assembled quantum dots embedded in the channel region of modulation-doped heterostructures is demonstrated. At room temperature, the detector shows a low dark current ranging in the nano-amperes at a bias voltage of 10 V. After the optimization of the separation between the quantum dot region and the 2DEG, a peak responsivity of 5.3 A/W is obtained at 9.0 μm. The high detectivities of 6×10⁸ and 5×10¹⁰ cmHz^1/2/W are obtained at room temperature and 80 K, respectively     

DC and AC characteristics ofAL0.25Ga0.75As/GaAs quantum-well delta-dopedchannel FET grown by LP-MOCVD

Al_0.25Ga_0.75As/GaAs quantum well delta-doped channel FETs (QWDFETs) have been successfully fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The FETs with a gate dimension of 1.8 μm×100 μm had a maximum extrinsic transconductance of 190 mS/mm and a maximum current density of 425 mA/mm. The device showed extremely broad transconductances around its peak. The S-parameter measurements indicated that the current gain and power gain cutoff frequencies of the device were 7 and 15 GHz, respectively. The transconductance versus gate voltage profiles showed a plateau region through a range of 1.7 V supporting spatial confinement of the electrons. These values are among the best reported for delta-doped GaAs-based FETs with a similar device geometry     

10 A, 2.4 kV Power DiMOSFETs in 4H-SiC

We report the characteristics of large area (3.3 × 3.3 mm ²) high-voltage 4H-SiC DiMOSFETs. The MOSFETs show a peak MOS channel mobility of 22 cm²/V·s and a threshold voltage of 8.5 V at room temperature. The DiMOSFETs exhibit an on-resistance of 4.2 mΩ·cm² at room temperature and 85 mΩ·cm² at 200°C. Stable avalanche characteristics at approximately 2.4 kV are observed. An on-current of 10 A is measured on a 0.103 cm² device. High switching speed is also demonstrated. This suggests that the devices are capable of high-voltage, high-frequency, low-loss switching applications     

Enhancement-mode Al0.66In0.34As/Ga0.67In0.33As metamorphic HEMT, modeling and measurements

This paper exhibits experimental and theoretical results on metamorphic high-electron mobility transistor (MM-HEMT). Modeling and measurements provide a better knowledge of device physics which allows us to optimize device structures. We present 10-GHz power performances, pulse and gate measurements, and two-dimensional (2-D) hydrodynamic modeling of enhancement-mode (E-mode) Al_0.66In_0.34As/Ga_0.67In_0.33 As NM-HEMT devices. It is the first time that cap layer thickness has been studied for a MM-HEMT. A typical reverse breakdown voltage of 16 V has been obtained. Gate current issued from impact ionization has been shown, for the first time, in such a device. The 2-D hydrodynamic model is a useful tool for cost engineering because it brings more information in terms of physical quantity distributions, necessary to predict breakdown behavior of FET. The 10-GHz measurements with a load-pull power set-up demonstrate the capabilities for a thick cap device with large gate-to-drain extension since an output power of 140 mW/mm have been obtained which is the state-of-the-art for such a device. These results obtained confirm the great interest of the structures for power application systems. The only work reported, to our knowledge, using a MM-HEMT structure in E-mode with an indium content close to 50% has been studied by Eisenbeiser et al.. Their typical gate-to-drain breakdown voltage was 5.2 V. The 0.6 μm ×3 mm devices exhibited 30 mW/mm at 850 MHz