Wang Xiantai

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.

An 8 GHz high power AlGaN/GaN HEMT VCO

A high power X-band hybrid microwave integrated voltage controlled oscillator (VCO) based on AlGaN/GaN HEMT is presented. The oscillator design utilizes a common-gate negative resistance structure with open and short-circuit stub microstrip lines as the main resonator for a high Q factor. The VCO operating at 20 V drain bias and −1.9 V gate bias exhibits an output power of 28 dBm at the center frequency of 8.15 GHz with an efficiency of 21%. Phase noise is estimated to be −85 dBc/Hz at 100 kHz offset and −128 dBc/Hz at 1 MHz offset. The tuning range is more than 50 MHz. The dominating effect of GaN HEMTs flicker noise on oscillator phase noise performance has also been discussed. The measured results show great promise for AlGaN/GaN HEMT technology to be used in high power and low phase noise microwave source applications.

0.15-μm T-gate In0.52Al0.48As/In0.53Ga0.47As InP-based HEMT with fmax of 390 GHz

In this paper, 0.15-μm gate-length In0.52Al0.48As/In0.53Ga0.47As InP-based high electron mobility transistors (HEMTs) each with a gate-width of 2 × 50 μm are designed and fabricated. Their excellent DC and RF characterizations are demonstrated. Their full channel currents and extrinsic maximum transconductance (gm,max) values are measured to be 681 mA/mm and 952 mS/mm, respectively. The off-state gate-to-drain breakdown voltage (BVGD) defined at a gate current of −1 mA/mm is 2.85 V. Additionally, a current-gain cut-off frequency (fT) of 164 GHz and a maximum oscillation frequency (fmax) of 390 GHz are successfully obtained; moreover, the fmax of our device is one of the highest values in the reported 0.15-μm gate-length lattice-matched InP-based HEMTs operating in a millimeter wave frequency range. The high gm,max, BVGD, fmax, and channel current collectively make this device a good candidate for high frequency power applications.

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.

A 6 GHz high power and low phase noise VCO using an InGaP/GaAs HBT

A 6 GHz voltage controlled oscillator (VCO) optimized for power and noise performance was designed and characterized. This VCO was designed with the negative-resistance (Neg-R) method, utilizing an InGaP/GaAs hetero-junction bipolar transistor in the negative-resistance block. A proper output matching network and a high Q stripe line resonator were used to enhance output power and depress phase noise. Measured central frequency of the VCO was 6.008 GHz. The tuning range was more than 200 MHz. At the central frequency, an output power of 9.8 dBm and phase noise of -122.33 dBc/Hz at 1 MHz offset were achieved, the calculated RF to DC efficiency was about 14%, and the figure of merit was -179.2 dBc/Hz.

W-band push—push monolithic frequency doubler in 1-μm InP DHBT technology

A W-band frequency doubler MMIC is designed and fabricated using 1-μm InP DHBT technology. Active balun is employed to transform the single-ended signal into differential output. Push—push configuration loaded with harmonic resonant network is utilized to acquire the second harmonic frequency. A multi-stage differential structure improves the conversion gain and suppresses the fundamental frequency. The MMIC occupies an area of 0.55 × 0.5 mm2 with 18 DHBTs integrated. Measurements show that the output power is above 5.8 dBm with the suppression of fundamental frequency below −16 dBc and the conversion gain above 4.7 dB over 75–80 GHz.

Sub 100 nm In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As InP-based HEMT with f T =204 GHz, f max =352 GHz, and g m, max =918 mS/mm

88 nm-gate InP-based InAlAs/InGaAs HEMTs with the gate width of 75 μm have been designed and fabricated. They exhibited a current gain cutoff frequency (f<inf>T</inf>) of 204 GHz and a maximum oscillation frequency (f<inf>max</inf>) of 352 GHz at a drain-source voltage (V<inf>ds</inf>) of 1.5 V and a gate-source voltage (V<inf>gs</inf>) of 0 V. Excellent DC characteristics were also demonstrated with the DC peak transconductance (g<inf>m, max</inf>) of 918 mS/mm and the maximum current density of 635 mA/mm.

Extrinsic Base Surface Passivation in High Speed “Type-II" GaAsSb/InP DHBTs Using an InGaAsP Ledge Structure

Type-II GaAsSb/InP DHBTs with selectively-etched InGaAsP ledge structures are fabricated and characterized for the first time. The novel InGaAsP/GaAsSb/InP DHBTs with a 20 nm lattice-matched GaAsSb base and a 75 nm InP collector have a dc current gain improvement by a factor of 2 and a cutoff frequency fT of 190 GHz. The InGaAsP ledge design provides a simple but effective approach to suppress the extrinsic base surface recombination and enable GaAsSb/InP DHBTs to further increase the operating frequencies and integration levels for millimeter wave applications.