Su Yongbo

100-nm T-gate InAlAs/InGaAs InP-based HEMTs with fT = 249 GHz and fmax = 415 GHz

InAlAs/InGaAs high electron mobility transistors (HEMTs) on an InP substrate with well-balanced cutoff frequency fT and maximum oscillation frequency fmax are reported. An InAlAs/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 OMmm. Moreover, the fT obtained in this work is the highest ever reported in 100-nm gate length InAlAs/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.

An 88 nm gate-length In0.53Ga0.47As/In0.52Al0.48As InP-based HEMT with fmax of 201 GHz

An 88 nm gate-length In0.53Ga0.47As/In0.52Al0.48As InP-based high electron mobility transistor (HEMT) was successfully fabricated with a gate width of 2 × 50 μm and source-drain space of 2.4 μm. The T-gate was defined by electron beam lithography in a trilayer of PMMA/Al/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 current, 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.

A Physics-Based Charge-Control Model for InP DHBT Including Current-Blocking Effect

We develop a physics-based charge-control InP double heterojunction bipolar transistor model including three important effects: current blocking, mobile-charge modulation of the base-collector capacitance and velocity-field modulation in the transit time. The bias-dependent base-collector depletion charge is obtained analytically, which takes into account the mobile-charge modulation. Then, a measurement based voltage-dependent transit time formulation is implemented. As a result, over a wide range of biases, the developed model shows good agreement between the modeled and measured S-parameters and cutoff frequency. Also, the model considering current blocking effect demonstrates more accurate prediction of the output characteristics than conventional vertical bipolar inter company results.

High-breakdown-voltage submicron InGaAs/InP double heterojunction bipolar transistor with f(t)=170 GHz and f(max)=253GHz

The layer structure of InGaAs/InP double heterojunction bipolar transistor (DHBT) is designed to enhance the frequency performance and breakdown voltage. The composition-graded base structure is used to decrease the base transit time. The InGaAs setback layer and two highly doped InGaAsP layers are used to eliminate the conduction band spike of the collector. The submicron-emitter InGaAs/InP DHBT is fabricated successfully. The base contact resistance is greatly decreased by optimization of contact metals. The breakdown voltage is more than 6 V. The current gain cutoff frequency is as high as 170 GHz and the maximum oscillation frequency reached 253 GHz. The DHBT with such high performances can be used to make W-band power amplifier.

High-Speed InGaAs/InP Double Heterostructure Bipolar Transistor with High Breakdown Voltage

We design and fabricate an InGaAs/InP double heterostructure bipolar transistor (DHBT). The spike of the conduction band discontinuity between InGaAs base and InP collector is successfully eliminated by insertion of an InGaAs layer and two InGaAsP layers. The current gain cutoff frequency and maximum oscillation frequency are as high as 155 and 144 GHz. The breakdown voltage in common-emitter configuration is more than 7 V. The high cutoff frequency and high breakdown voltage make high-speed and high-power circuits possible.

High current multi-finger InGaAs/InP double heterojunction bipolar transistor with the maximum oscillation frequency 253 GHz

A four-finger InGaAs/InP double heterojunction bipolar transistor is designed and fabricated successfully by using planarization technology. The emitter area of each finger is 1 ? 15?m2. The breakdown voltage is more than 7 V, the maximum collector current could be more than 100 mA. The current gain cutoff frequency is as high as 155 GHz and the maximum oscillation frequency reaches 253 GHz. The heterostructure bipolar transistor can offer more than 70mW class-A maximum output power at W band and the maximum power density can be as high as 1.2W/mm.

A symbolically defined InP double heterojunction bipolar transistor large-signal model

A self-built accurate and flexible large-signal model based on an analysis of the characteristics of InP double heterojunction bipolar transistors (DHBTs) is implemented as a seven-port symbolically defined device (SDD) in Agilent ADS. The model accounts for most physical phenomena including the self-heating effect, Kirk effect, soft knee effect, base collector capacitance and collector transit time. The validity and the accuracy of the large-signal model are assessed by comparing the simulation with the measurement of DC, multi-bias small signal S parameters for InP DHBTs.

Composite-Collector InGaAs/InP Double Heterostructure Bipolar Transistors with Current-Gain Cutoff Frequency of 242 GHz

To eliminate the conduction band spike at the base-collector interface, an InP/InGaAs double heterostructure bipolar transistor (DHBT) with an InGaAsP composite collector is designed and fabricated using the conventional mesa structure. The DHBT with emitter area of 1.6 × 15 μm2 exhibits current-gain cutoff frequency ft = 242 GHz at the high collector current density Jc = 2.1 mA/μm2, which is to our knowledge the highest ft reported for the mesa InP DHBT in China. The breakdown voltage in common-emitter configuration is more than 5 V. The high-speed InP/InGaAs DHBT with high current density is very suitable for the application in ultra high-speed digital 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 (Lside) of 300, 412 and 1070 nm were analyzed. With the increase in Lside, 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 Lside. Meanwhile, the Lside 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.

Ultra high-speed InP/InGaAs SHBTs with/t and/max of 185 GHz

An InP/InGaAs single heterojunction bipolar transistor (SHBT) with high maximum oscillation frequency (fmax) and high cutoff frequency (ft) is reported. Efforts have been made to maximize fmax and ft simultaneously including optimizing the epitaxial structure, base-collector mesa over-etching and base surface preparation. The measured ft and fmax both reached 185 GHz with an emitter size of 1 × 20 μm2, which is the highest fmax for SHBTs in mainland China. The device is suitable for ultra-high speed digital circuits and low power analog applications.