Egor Alekseev

Capacitance–voltage characterization of AlN/GaN metal–insulator–semiconductor structures grown on sapphire substrate by metalorganic chemical vapor deposition

Electrical characterization of AlN/GaN interfaces was carried out by the capacitance–voltage (C–V) technique in materials grown by metalorganic chemical vapor deposition. The high-frequency C–V characteristics showed clear deep-depletion behavior at room temperature, and the doping density derived from the slope of 1/C2 plots under the deep depletion condition agreed well with the growth design parameters. A low value of interface state density Dit of 1×1011 cm−2 eV−1 or less around the energy position of Ec−0.8 eV was demonstrated, in agreement with an average Dit value estimated from photoassisted C–V characteristics.

Large-signal microwave performance of GaN-based NDR diode oscillators

The GaN material parameters relevant to the negative diAerential resistance (NDR) devices are discussed, and their physical models based on the theoretical predictions and experimental device characteristics are introduced. Gunn diode design criteria were applied to design the GaN NDR diodes. A higher electrical strength of the GaN allowed operation with higher doping (10 17 cm ˇ3 ) and at a higher bias (90 V for a 3 lm thick diode). The transient hydrodynamic simulations were used to carry out the harmonic power analysis of the GaN NDR diode oscillators in order to evaluate their large-signal microwave characteristics. The GaAs Gunn diode oscillators were also simulated for a comparison and verification purposes. The dependence of the oscillation frequency and output power on the GaN NDR diode design and operating conditions are reported. It was found that, due to the higher electron velocities and reduced time constants, GaN NDR diodes oAered twice the frequency capability of the GaAs Gunn diodes (87 GHz vs. 40 GHz), while their output power density was 2 10 5 W/cm 2 compared with10 3 W/cm 2 for the GaAs devices. The reported improvements in the microwave performance are supported by the high value of the GaN Pf 2 Z figure of merit, which is 50‐100 times higher than the GaAs, indicating a strong potential of the GaN for the microwave signal generation. ” 2000 Elsevier Science Ltd. All rights reserved.

DC and high-frequency performance of AlGaN/GaN Heterojunction Bipolar Transistors

The DC and high frequency performance of AlGaN/GaN Heterojunction Bipolar Transistors (HBTs) is analyzed using an enhanced drift-diAusion model and GaN/AlGaN material parameters, which were previously verified by modeling experimental device characteristics. The emitter‐base diode turn-on voltage is as high as 2.7 V while the collector and base ideality factors are 1.16 and 1.46 respectively. A DC current gain of b=15 is found at a collector current density of 2.5 kA/cm 2 and the gain is maintained at this value up to 4.1 kA/cm 2 . The devices show a small oAset voltage of 0.5 V. A forward breakdown voltage BVCEO of 70 V is found for designs with collector doping of 5 10 16 cm ˇ3 . The current gain varied from 22 to 6 when the base doping was increased from 5 10 17 to 2 10 18 cm ˇ3 . At the same time, the maximum oscillation frequency fMAX increased from 3 to 6 GHz. A severe degradation of the current gain, fT, and fMAX was observed for HBT designs with a base thickness wider than 1000 A˚ .B y optimizing the transistor design and bias, an fT of 44 GHz and an fMAX of 24 GHz are predicted. Results of a large-signal analysis are also presented to evaluate the power capability and eAciency of AlGaN/GaN HBTs. # 2000 Elsevier Science Ltd. All rights reserved.

77 GHz high-isolation coplanar transmit-receive switch using InGaAs/InP PIN diodes

InP-based InGaAs PIN millimeter-wave diodes were used to design and fabricate monolithic integrated transmit-receive switches for W-band automotive applications. Coplanar-waveguide InGaAs PIN diode technology with reduced parasitics was employed for fabricating MMICs and yielded switches with high isolation and low insertion loss as shown by the performance of W-band single-pole double-throw switches. 77 GHz SPDT switches demonstrated less than 1.35 dB insertion loss, more than 43 dB input-to-output isolation, and more than 30 dB output-to-output crosstalk. W-band on-wafer large-signal characterization revealed no degradation of performance when the input power was increased to the maximum available level of +11 dBm.

Power performance and scalability of AlGaN/GaN power MODFETs

The scalability of power performance of AlGaN/GaN MODFETs with large gate periphery, as necessary for microwave power devices, is addressed in this paper. High-frequency large-signal characteristics of AlGaN/GaN MODFETs measured at 8 GHz are reported for devices with gatewidths from 200 /spl mu/m to 1 mm. 1-dB gain compression occurred at input power levels varying from -1 to +10 dBm as the gatewidth increased, while gain remained almost constant at -17 dB. Output power density was /spl sim/1 W/mm for all devices and maximum output power (29.9 dBm) occurred in devices with 1-mm gates, while power-added efficiency remained almost constant at /spl sim/30%. The large-signal characteristics were compared with those obtained by dc and small-signal S-parameters measurements. The results illustrate a notable scalability of AlGaN/GaN MODFET power characteristics and demonstrate their excellent potential for power applications.

GaN Gunn diodes for THz signal generation

The frequency and power capability of GaN-based Gunn diodes are evaluated using transient hydrodynamic simulations. GaN Gunn oscillators with 2 /spl mu/m-thick GaN Gunn diodes are predicted to have a fundamental frequency of 148-162 GHz and power density of >10/sup 5/ W/cm/sup 2/. Due to their high frequency and power characteristics, applications of these devices are envisaged for THz signal generation.

Broadband AlGaN/GaN HEMT MMIC Attenuators with High Dynamic Range

GaN-based HEMT Microwave Monolithic Integrated Circuit (MMIC) attenuators were realized for the first time. The MMICs employed AlGaN/GaN HEMTs fabricated by optical contact lithography (Lg=1¿m) with high current gain (fT) and maximum power gain (fMAX) cutoff frequencies of 17 and 24GHz, respectively. The MMIC attenuators employing three 100¿m-wide AlGaN/GaN HEMTs in ¿-configuration had minimum insertion of 4dB, high dynamic range (>30dB), and broadband operation (up to 18GHz). On-wafer power characterization at 8GHz confirmed successful operation of the GaN-based attenuator MMICs at power density exceeding 15W/mm.

W-band on-wafer load-pull measurement system and its application to HEMT characterization

An on-wafer large-signal characterization system has been developed for W-band frequency applications. The system is computer-controlled and employs a high-precision electromechanical W-band tuner. Its application to obtaining constant output power and gain contours as well as power saturation characteristics of submicron InP-based HEMTs is demonstrated at 77 GHz and 102 GHz.

InP-based and metamorphic devices for multifunctional MMICs in mm-wave communication systems

In this paper, the performances of our InP-based and metamorphic HFETs are compared. Measurements on the RF as well as the noise behaviour are presented. Furthermore, first results are demonstrated on the integration of the InP-based PIN diode and HFET on one InP-substrate. Using these two devices, we integrated three different MMIC designs on one wafer: SPDT switch, phaseshifter and a combination of SPDT switch and LNA for a multifunctional MMIC.

Power-handling capability of W-band InGaAs pin diode switches

The power-handling capability of InGaAs pin diodes is reported and compared to that of GaAs pin diodes. The trade-off between power handling, high frequency performance, and bias conditions is considered. W-band InGaAs pin diode monolithic switches were fabricated using coplanar-waveguide technology, and their large-signal characteristics measured using a W-band load-pull characterization system are reported for the first time.