Characteristics and threshold voltage model of GaN-based FinFET with recessed gate

In this work, AlGaN/GaN FinFETs with different fin widths have been successfully fabricated, and the recessed-gate FinFETs are fabricated for comparison. The recessed-gate FinFETs exhibit higher transconductance value and positive shift of threshold voltage. Moreover, with the fin width of the recessed-gate FinFETs increasing, the variations of both threshold voltage and the transconductance increase. Next, transfer characteristics of the recessed-gate FinFETs with different fin widths and recessed-gate depths are simulated by Silvaco software. The relationship between the threshold voltage and the AlGaN layer thickness has been investigated. The simulation results indicate that the slope of threshold voltage variation reduces with the fin width decreasing. Finally, a simplified threshold voltage model for recessed-gate FinFET is established,which agrees with both the experimental results and simulation results.

GaN metal-oxide-semiconductor field-effect transistors on AIGaN/GaN heterostructure with recessed gate

GaN metal-oxide-semiconductor field-effect transistors （MOSFETs） on AIGaN/GaN heterostructure with a recess gate were fabricated and characterized. The device showed good pinch-off characteristics and a maximum field-effect mobility of 145.2 cm2.V-1.s-1. The effects of etching gas of CI2 and SiCI4 were investigated in the gate recess process. SiCI4-etched devices showed higher channel mobility and lower threshold voltage. Atomic force microscope measurement was done to investigate the etching profile with different etching protection mask. Compared with photoresist, SiO2- masked sample showed lower surface roughness and better profile with stepper sidewall and weaker trenching effect resulting in higher channel mobility in the MOSFET.

100-nm T-gate InAlAs/InGaAs InP-based HEMTs with f_T = 249 GHz and f_(max) = 415 GHz

InA1As/InGaAs high electron mobility transistors （HEMTs） on an InP substrate with well-balanced cutoff frequency fT and maximum oscillation frequency frnax are reported. An InA1As/InGaAs HEMT with 100-nm gate length and gate width of 2 × 50 μm shows excellent DC characteristics, including full channel current of 724 mA/mm, extrinsic maximum transconductance gm.max of 1051 mS/mm, and drain-gate breakdown voltage BVDG of 5.92 V. In addition, this device exhibits fT = 249 GHz and fmax = 415 GHz. These results were obtained by fabricating an asymmetrically recessed gate and minimizing the parasitic resistances. The specific Ohmic contact resistance was reduced to 0.031 0.mm. Moreover, the fT obtained in this work is the highest ever reported in 100-nm gate length InA1As/InGaAs InP-based HEMTs. The outstanding gm.max, fT, fmax, and good BVDG make the device suitable for applications in low noise amplifiers, power amplifiers, and high speed circuits.

Impact of gate offset in gate recess on DC and RF performance of InAlAs/InGaAs InP-based HEMTs

A set of 100-nm gate-length In P-based high electron mobility transistors(HEMTs)were designed and fabricated with different gate offsets in gate recess.A novel technology was proposed for independent definition of gate recess and T-shaped gate by electron beam lithography.DC and RF measurement was conducted.With the gate offset varying from drain side to source side,the maximum drain current(I_(ds,max))and transconductance(g_(m,max))increased.In the meantime,fTdecreased while f;increased,and the highest fmax of 1096 GHz was obtained.It can be explained by the increase of gate-source capacitance and the decrease of gate-drain capacitance and source resistance.Output conductance was also suppressed by gate offset toward source side.This provides simple and flexible device parameter selection for HEMTs of different usages.

30 nm T-gate enhancement-mode InAIN/AIN/GaN HEMT on SiC substrates for future high power RF applications

The DC and RF performance of 30 nm gate length enhancement mode （E-mode） InAlN/AIN/GaN high electron mobility transistor （HEMT） on SiC substrate with heavily doped source and drain region have been inves- tigated using the Synopsys TCAD tool. The proposed device has the features of a recessed T-gate structure, lnGaN back barrier and Al2O3 passivated device surface. The proposed HEMT exhibits a maximum drain current density of 2.1 A/mm, transconductance gm of 1050 mS/mm, current gain cut-off frequency f of 350 GHz and power gain cut-off frequency fmax of 340 GHz. At room temperature the measured carrier mobility （μ）, sheet charge carrier density （ns） and breakdown voltage are 1580 cm2/（V.s）, 1.9× 1013 cm-2, and 10.7 V respectively. The superla- tives of the proposed HEMTs are bewitching competitor or future sub-millimeter wave high power RF VLSI circuit applications.

An 88 nm gate-length In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As InP-based HEMT with f_(max) of 201 GHz

An 88 nm gate-length In0.53Ga0.47As/In0.52Alo.48As InP-based high electron mobility transistor （HEMT） was successfully fabricated with a gate width of 2× 50 μm and source-drain space of 2.4μm. The T-gate was defined by electron beam lithography in a trilayer of PMMA/A1/UVIII. The exposure dose and the development time were optimized, and followed by an appropriate residual resist removal process. These devices also demonstrated excellent DC and RF characteristics： the extrinsic maximum transconductance, the full channel cur- rent, the threshold voltage, the current gain cutoff frequency and the maximum oscillation frequency of the HEMTs were 765 mS/mm, 591 mA/mm, -0.5 V, 150 GHz and 201 GHz, respectively. The HEMTs are promising for use in millimeter-wave integrated circuits.

Impact of the lateral width of the gate recess on the DC and RF characteristics of InAlAs/InGaAs HEMTs

We fabricated 88 nm gate-length InP-based InAlAs/InGaAs high electron mobility transistors（HEMTs） with a current gain cutoff frequency of 100 GHz and a maximum oscillation frequency of 185 GHz.The characteristics of HEMTs with side-etched region lengths（L_（Side）） of 300,412 and 1070 nm were analyzed.With the increase in L_（Side）,the kink effect became notable in the DC characteristics,which resulted from the surface state and the effect of impact ionization.The kink effect was qualitatively explained through energy band diagrams,and then eased off by reducing the L_（Side）.Meanwhile,the L_（Side） dependence of the radio frequency characteristics,which were influenced by the parasitic capacitance,as well as the parasitic resistance of the source and drain,was studied.This work will be of great importance in fabricating high-performance InP HEMTs.