Gate-drain Breakdown Voltage Research Articles

Investigations on In0.45Al0.55As ∕ InxGa1 − xAs Metamorphic High-Electron-Mobility Transistors with Double Gate-Recess and SiNx Passivation

Comparative investigations on linearly graded metamorphic high-electron-mobility transistors (MHEMTs) with/without applying surface passivation or double-gate-recess techniques have been comprehensively made in this work. The proposed double-gate-recessed, -passivated MHEMT with gate dimensions of has demonstrated superior extrinsic transconductance of , gate-drain breakdown voltage of , intrinsic voltage gain of 69, saturated output power of , and power-added efficiency of 53.8%, due to its enhanced gate-modulation capability, suppressed gate leakages, and relieved kink effects. The proposed device can be promisingly applied to high-gain and high-power millimeter-wave integrated circuit technologies.

Effect of the non-annealed ohmic-recess approach on temperature-dependent properties of a metamorphic high electron mobility transistor

The reliability-related properties of an InAlAs/InGaAs metamorphic high electron mobility transistor (MHEMT), using the non-annealed ohmic-recess (NAOR) approach, are studied and demonstrated. The NAOR device shows significantly improved dc and radio frequency (RF) performance over a wide temperature range (300–500 K). With a 1 × 100 µm2 gate-dimension MHEMT by the NAOR approach, the considerably improved thermal stability and dc performances, including lower temperature variation coefficients on turn-on voltage (−1.38 mV K−1) and gate-drain breakdown voltage (−30.4 mV K−1), and on-resistance (2.41 × 10−3 Ω mm K−1), are obtained as the temperature is increased from 300 to 500 K. For RF characteristics, the NAOR device also shows a low degradation rate on drain saturation current operating regimes (−5.52 × 10−4 K−1) as the temperature is increased from 300 to 400 K. In addition, based on the lifetime tests, an activation energy of 1.33 eV and a projected median lifetime of 1.2 × 107 h at Tch = 125 °C are obtained for the NAOR MHEMT.

Comparative influence study of gate-formation structuring on Al0.22Ga0.78As/In0.16Ga0.84As/Al0.22Ga0.78As double heterojunction high electron mobility transistors

Pseudomorphic Al0.22Ga0.78As/In0.16Ga0.84As/Al0.22Ga0.78As double heterojunction high electron mobility transistors (DH-HEMTs) fabricated with different gate-formation structures of a single-recess gate (SRG), a double-recess gate (DRG) and a field-plate gate (FPG) were comparatively investigated. FPG devices show the best breakdown characteristics among these devices due to great reduction in the peak electric field between the drain and gate electrodes. The measured gate–drain breakdown voltages defined at a 1 mA mm−1 reverse gate–drain current density were −15.3, −19.1 and −26.0 V for SRG, DRG and FPG devices, respectively. No significant differences in their room-temperature common-source current–voltage characteristics were observed. However, FPG devices exhibit threshold voltages being the least sensitive to temperature. Threshold voltages as a function of temperature indicate a threshold-voltage variation as low as −0.97 mV K−1 for FPG devices. According to the 2.4 GHz load–pull power measurement at VDS = 3.0 V and VGS = −0.5 V, the saturated output power (POUT), power gain (GP) and maximum power-added efficiency (PAE) were 10.3 dBm/13.2 dB/36.6%, 11.2 dBm/13.1 dB/39.7% and 13.06 dBm/12.8 dB/47.3%, respectively, for SRG, DRG and FPG devices with a pi-gate in class AB operation. When the FPG device is biased at a VDS of 10 V, the saturated power density is more than 600 mW mm−1.

Influence of Field Plates and Surface Traps on Microwave Silicon Carbide MESFETs

The influence of field plates and surface traps on silicon carbide MESFETs for microwave operation was investigated. By increasing the length of gate-connected field plates from 50 to 800 nm, it was possible to increase the gate-drain breakdown voltage of the devices from 125 to 170 V. At the same time, the current slump effect of traps in the passivation oxide was reduced. By using a combination of field plates and a passivation oxide with low interface trap density, it was possible to reach an output power density of 8 W/mm at 3 GHz.

High performance 1 mm AlGaN/GaN HEMT based on SiC substrate

This is our first report on the high performance 1 mm AlGaN/GaN high electron mobility transistor (HEMT) which was developed using home-made AlGaN/GaN epitaxy structures based on SiC substrate. Metal-organic chemical vapor deposition (MOCVD) was used to generate the epitaxy layers. Corresponding experiments show that the device has a gate length of 0.8 μm exhibiting drain current density of 1.16 A/mm, transconductance of 241 ms/mm, a gate-drain breakdown voltage larger than 80 V, maximum current gain frequency of 20 GHz and maximum power gain frequency of 28 GHz. In addition, the power gain under the continues wave condition is 14.2 dB with a power density of 4.1 W/mm, while under the pulsed wave condition, power gain reaches 14.4 dB with power density at 5.2 W/mm. Furthermore, the two-port network impedance characteristics display great potential in microwave application.

Performance of AlGaAs ∕ InGaAs ∕ GaAs Pseudomorphic High Electron Mobility Transistor as a Function of Temperature

An pseudomorphic high electron mobility transistor (pHEMT) with double δ-doping carrier supply layers was fabricated and characterized. Estimates of typical device characteristics (extrinsic transconductance , drain current density , threshold voltage , current gain cut-off frequency , maximum frequency of oscillation , noise behavior, and large signal measurements) were made. A series of experiments was conducted to assess the effects of temperature on pHEMT. A peak of was obtained from the fabricated pHEMT with a gate length of for room-temperature operation. The transistor characteristics showed evidence of high breakdown voltages. With respect to the variation in two-terminal gate-drain breakdown voltage, this device had a positive temperature coefficient from , and a negative temperature coefficient at temperatures surpassing . Strikingly, high-frequency on-wafer measurements on the fabricated pHEMT were made up to , revealing nearly no change in . Not only was the device characterized and the complicated mechanisms at various temperatures elucidated, but also the favorable potential of the presented pHEMT for high-temperature and high-frequency applications was determined.

Control of GaAs-MESFET breakdown voltage by Shannon implantation

The dependence of GaAs-MESFET gate-drain breakdown voltage on gate-Schottky barrier enhancement by Shannon-implantation is analyzed. The analytical results show that the breakdown voltage can be increased by increasing the Shannon-implant dose. However, the tolerable limit of hole accumulation under the gate does not allow the breakdown voltage to be increased beyond a certain limit. The breakdown voltage limit is higher for a channel of lighter doping. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An AlGaN/GaN HEMT power switch employing a field plate and a floating gate

We have proposed and fabricated AlGaN/GaN high electron mobility transistors (HEMTs) which increase the gate-drain breakdown voltage by employing a floating gate and a field plate. Experimental results show that the breakdown voltage of the proposed devices was successfully increased compared with that of the devices which employ only the floating gate in our previous report. High breakdown voltage of 484 V is obtained while the breakdown voltage of the conventional devices is 250 V. The leakage current is reduced considerably from 88 to 8.5 μA by employing the additional field plate. Measurement of dynamic characteristics shows that the proposed devices operate under high frequency inductive load switching without any current dispersion.

Temperature dependences of an In0.46Ga0.54As/In0.42Al0.58As based metamorphic high electron mobility transistor (MHEMT)

In this paper, an interesting thermally stable In0.42Al0.58As/In0.46Ga0.54As metamorphic high electron mobility transistor (MHEMT) is fabricated and investigated. Good dc and RF characteristics are obtained by precisely depositing gold (Au) upon the In0.42Al0.58As barrier layer as the Schottky contact metal. For a MHEMT with gate dimensions of 1 × 100 µm2, high gate–drain breakdown voltage, high turn-on voltage, low gate leakage current density, high maximum transconductance with broad operating regime and low output conductance are obtained even at ambient temperatures up to 510 K (240 °C). The studied device also shows a very good microwave performance at room temperature. Moreover, the relatively low variations of the device performance are achieved over a wide temperature range (from 300 to 510 K). Therefore, the studied device has a good thermally stable performance that is suitable for high-speed and high-power electronic applications.

Thermal-Stability Improvement of a Sulfur-Passivated InGaP/InGaAs/GaAs HFET

The temperature-dependent characteristics of an InGaP/InGaAs/GaAs heterostructure field-effect transistor (HFET), using the (NH/sub 4/)/sub 2/S/sub x/ solution to form the InGaP surface passivation, are studied and demonstrated. The sulfur-passivated device shows significantly improved dc and RF performances over a wide temperature range (300-510 K). With a 1/spl times/100-/spl mu/m/sup 2/ gate-dimension HFET by (NH/sub 4/)/sub 2/S/sub x/ treatment, the considerably improved thermal stability over dc performances including lower temperature variation coefficients on the turn-on voltage (-1.23 mV/K), the gate-drain breakdown voltage (-0.05 mV/K), the gate leakage current (1.04 /spl mu/A/mm/spl middot/K), the threshold voltage (-1.139 mV/K), and the drain-saturation-current operating regimes (-3.11/spl times/10/sup -4//K) are obtained as the temperature is increased from 300 to 510 K. In addition, for RF characteristics, the sulfur-passivated device also shows a low degradation rate on drain-saturation-current operating regimes (-3.29/spl times/10/sup -4//K) as the temperature is increased from 300 to 400 K. These advantages provide the promise for high-speed high-frequency high-temperature electronics applications.

CW 140 W recessed-gate AlGaN/GaN MISFET with field-modulating plate

The recessed-gate AlGaN/GaN metal-insulator-semiconductor (MIS) FET with a field-modulating plate (FP) has been fabricated. At a reverse bias condition, gate-leakage current is 10−9 A/mm and gate-drain breakdown voltage is over 200 V, which is four times higher than that of a conventional AlGaN/GaN MISFET without an FP. At 2 GHz, a 48 mm-wide recessed MIS-FP-FET demonstrated a CW saturated output power of 141 W (2.9 W/mm), a linear gain of 7.6 dB and a power-added efficiency of 56% with a drain bias of 40 V. A total CW output power of 141 W is the highest ever achieved for any III-V compound-semiconductor MISFETs.

Power performance and scalability study of AlGaAs/GaAs double-recessed pseudomorphic high electron mobility transistors on unthinned substrate for coplanar waveguide circuit applications

We have investigated the power performance and scalability of AlGaAs/GaAs Double-Recessed Pseudomorphic High Electron Mobility Transistors (DR-PHEMTs) at 10 GHz on an unthinned GaAs substrate for CoPlanar Waveguide (CPW) circuit applications. It was found that the output power varied linearly with the logarithm of the device’s gate width ranging from 200 to 1000 μm. It increased at a rate of 0.01 dB/μm. That worked out to a doubling of output power (or 3 dB) for every 300 μm increase in the gate width. Gain decreased at a rate of about 0.005 dB/μm while PAE generally improved when the gate width was increased. As for DC measurement, the maximum transconductance of the device was about 375 mS/mm at V G = −0.5 V and V DS = 3 V. The gate-drain breakdown voltage (BV GD) measured was −20 V, defined at I G = −1 mA/mm. The microwave performance of the devices was measured on-wafer using a load-pull system at a bias of V G = −0.5 V and V DS = 8 V. For a device with a gate width of 1 mm, its saturated CW output power, gain and PAE value at 10 GHz was 27.5 dBm (0.55 W), 8 dB and 48%, respectively. At this same set of bias conditions, the value of f t and f max was 40 and 80 GHz, respectively.

GaAs MOSFET Using InAlP Native Oxide as Gate Dielectric

GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) using wet thermally oxidized InAlP as the gate insulator are reported for the first time. Leakage current measurements show that the 11-nm-thick native oxide grown from an In/sub 0.49/Al/sub 0.51/P layer lattice-matched to GaAs has good insulating properties, with a measured leakage current density of 1.39/spl times/10/sup -7/ mA//spl mu/m/sup 2/ at 1 V bias. GaAs MOSFETs with InAlP native gate oxide have been fabricated with gate lengths from 7 to 2 /spl mu/m. Devices with 2-/spl mu/m-long gates exhibit a peak extrinsic transconductance of 24.2 mS/mm, an intrinsic transconductance of 63.8 mS/mm, a threshold voltage of 0.15 V, and an off-state gate-drain breakdown voltage of 21.2 V. Numerical Poisson's equation solutions provide close agreement with the measured sheet resistance and threshold voltage.

Characteristics of a new camel-gate field effect transistor (CAMFET) with a composite channel structure

A new camel-gate field effect transistor (CAMFET) with a composite channel structure has been fabricated and demonstrated. Due to the n+-InGaP/p+-InGaP/GaAs camel gate and InGaAs/GaAs composite channel structures employed, good device performance is observed. Experimentally, at room temperature, a gate-drain breakdown voltage over 15 V, maximum transconductance gm,max of 111.5 mS mm−1, voltage gain AV of 93.4, unity current gain cut-off frequency fT of 16.2 GHz and maximum oscillation frequency unity fmax of 24.2 GHz are obtained simultaneously for a 1 × 100 µm2 device. The studied device also shows good properties in a higher temperature regime. Moreover, the studied device exhibits relatively negligible temperature-dependent characteristics over the operating temperature range from 300 to 420 K. Therefore, the studied device provides promise for high-temperature and high-performance microwave electronic applications.

179 W recessed-gate AlGaN∕GaN heterojunction FET with field-modulating plate

Microwave high-power performance has been achieved using a recessed-gate AlGaN/GaN heterojunction FET with a field-modulating plate. Making use of recessed-gate structure, the device exhibited an improved transconductance of 200 mS/mm with a maximum drain current of 900 mA/mm and a gate-drain breakdown voltage of 200 V. A 48 mm wide single-chip FET exhibited 179 W (3.7 W/mm) output power, 64% power-added efficiency, and 9.3 dB linear gain at a drain bias of 46 V. The saturated output power of 179 W is believed to be the highest ever achieved for any single-chip FETs.

10-W/mm AlGaN-GaN HFET with a field modulating plate

AlGaN-GaN heterojunction field-effect transistors (HFETs) with a field modulating plate (FP) were fabricated on an SiC substrate. The gate-drain breakdown voltage (BV/sub gd/) was significantly improved by employing an FP electrode, and the highest BV/sub gd/ of 160 V was obtained with an FP length (L/sub FP/) of 1 μm. The maximum drain current achieved was 750 mA/mm, together with negligibly small current collapse. A 1-mm-wide FP-FET (L/sub FP/=1 μm) biased at a drain voltage of 65 V demonstrated a continuous wave saturated output power of 10.3 W with a linear gain of 18.0 dB and a power-added efficiency of 47.3% at 2 GHz. To our knowledge, the power density of 10.3 W/mm is the highest ever achieved for any FET of the same gate size.

96 W AlGaN∕GaN heterojunction FET with field-modulating plate

An AlGaN/GaN heterojunction FET with a field-modulating plate has been successfully fabricated. A maximum drain current of 900 mA/mm was obtained with a gate–drain breakdown voltage of over 150 V. A 24 mm-wide FET exhibited 96 W (4.0 W/mm) output power, 54% power-added efficiency and 8.5 dB linear gain at a drain bias of 32 V.

Delta-doped AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors with high breakdown voltages

The fabrication and dc characteristics of AlGaN/GaN-based heterostructure field-effect transistors (HFETs) by employing the δ-doped barrier and the SiO2 insulated gate are reported. The device grown on sapphire substrate has a high drain-current-driving and gate-control capabilities as well as a very high gate-drain breakdown voltage of 200 V for a gate length of 1 μm and a source-drain distance of 3 μm. The incorporation of the SiO2 insulated gate and the δ-doped barrier into HFET structures reduces the gate leakage and improves the two-dimensional channel carrier mobility, and thereby allows one to take the inherent advantage of AlGaN/GaN HFETs with relatively high Al contents—the device structure is capable to deliver higher electron density (or drain current density) yet ensures an excellent pinch-off property as well as small gate leakage current. These characteristics indicate a great potential of this structure for high-power-microwave applications.

On the high-performance n +-GaAs/p +-InGaP/n-GaAs high-barrier gate camel-like HFETs

The high-performance n +-GaAs/p +-InGaP/n-GaAs high-barrier gate camel-like HFETs are successfully fabricated and demonstrated. The p +-InGaP layer is introduced to increase the barrier height and carrier confinement. Experimentally, good DC and AC device performances are obtained. For the studied 1×100 μm 2 device A (B), a gate–drain turn-on voltage of 1.6 (1.2) V, gate–drain breakdown voltage over 40 V with low leakage current of 400 (37) μA/mm, drain–source off-state breakdown voltage of 38 (39.7) V, maximum transconductance g m,max of 145 (147) mS/mm, unity current gain cut-off frequency f T of 17 (15) GHz, and maximum oscillation frequency f max of 33 (28) GHz are obtained, respectively, at room temperature. Moreover, the studied devices also show significantly wide and flat I DS operation regimes of g m, f T and f max.

Investigation of self-aligned p ++-GaAs/n-InGaP heterojunction field-effect transistors

p ++-GaAs/n-InGaP heterojunction field-effect transistors (HJFETs) with a highly carbon-doped gate and a wide-gap channel were reported. A self-aligned T-shaped gate HJFET exhibits a gate of 0.6 μm in length by depositing gate metal of 1.0 μm . DC characteristics including a turn-on voltage of 2.0 V at 1 mA/ mm , a gate-drain breakdown voltage up to 30 V , a drain-source breakdown voltage exceeding 25 V , a maximum available transconductance of 160 mS/ mm and AC performances such as a unit-current gain frequency of 16.8 GHz , and a unit-power gain frequency of 25 GHz were obtained for a non-self-aligned HJFET. With a self-aligned processing structure, the transconductance and f max were improved to 230 mS/ mm and 35 GHz , respectively.