Study on Electric Field Modulation and Avalanche Enhancement of SiC/GaN IMPATT Diode

This paper proposes a 6H-materials silicon carbide (SiC)/gallium nitride (GaN) heterogeneous p-n structure to replace the GaN homogenous p-n junction to manufacture an impact-ionization-avalanche-transit-time (IMPATT) diode, and the performance of this 6H-SiC/GaN heterojunction single-drift-region (SDR) IMPATT diode is simulated at frequencies above 100 GHz. The performance parameters of the studied device were simulated and compared with the conventional GaN p-n IMPATT diode. The results show that the p-SiC/n-GaN IMPATT performance is significantly improved, and this is reflected in the enhanced characteristics in terms of operating frequency, rf power, and dc-rf conversion efficiency by the two mechanisms. One such characteristic that the new structure has an excessive avalanche injection of electrons in the p-type SiC region owing to the ionization characteristics of the SiC material, while another is a lower electric field distribution in the drift region, which can induce a higher electron velocity and larger current in the structure. The work provides a reference to obtain a deeper understanding of the mechanism and design of IMPATT devices based on wide-bandgap semiconductor materials.

Study of p-SiC/n-GaN Hetero-Structural Double-Drift Region IMPATT Diode

Nowadays, the immature p-GaN processes cannot meet the manufacturing requirements of GaN impact ionization avalanche transit time (IMPATT) diodes. Against this backdrop, the performance of wide-bandgap p-SiC/n-GaN heterojunction double-drift region (DDR) IMPATT diode is investigated in this paper for the first time. The direct-current (DC) steady-state, small-signal and large-signal characteristics are numerically simulated. The results show that compared with the conventional GaN single-drift region (SDR) IMPATT diode, the performance of the p-SiC/n-GaN DDR IMPATT proposed in this design, such as breakdown voltage, negative conductance, voltage modulation factor, radio frequency (RF) power and DC-RF conversion efficiency have been significantly improved. At the same time, the structure proposed in this design has a larger frequency bandwidth. Due to its greater potential in the RF power density, which is 1.97 MW/cm2 in this study, indicates that the p-SiC/n-GaN heterojunction provides new possibilities for the design and manufacture of IMPATT diode.

Analysis of Electrical and Thermal Models for Pulsed IMPATT Diode Simulation

Some nonlinear models are presented for modeling and analyzing IMPATT high-power pulse diodes. These models are suitable for analyzing different operating modes of the oscillator. The first model is a precise one, which describes all important electrical phenomena on the basis of the continuity equations and Poisson´s equation, and it is correct until 300 GHz. The second approximate mathematical model suitable for the analysis of IMPATT diode stationary operation oscillator and for optimization of internal structure of the diode. The temperature distribution in the semiconductor structure is obtained using the special thermal model of the IMPATT diode, which is based on the numerical solution of the non-linear thermal conductivity equation. The described models can be applied for the analysis, optimization and practical design of pulsedmode millimetric IMPATT diodes. It can also be used to evaluate the thermal behavior of diodes, to correctly select the shape and amplitude of a supply pulse, and to design various types of high-power pulsed millimeter IMPATT diodes with a complex doping profile with improved characteristics.

IMPATT Efficiency Extraction Using On-Chip Antenna Radiation

IMPATT diodes were designed and integrated with microstrip patch antenna on–chip in standard CMOS technology to extract the efficiency beyond avalanche frequency. By comparing the on-chip simulations and measurements of an IMPATT diode integrated in a CPW to an integrated one with a microstrip patch antenna at the same biasing conditions, the results demonstrated an efficiency ranging from ~ 0.01% to 0.016% without and with the added surface roughness losses, respectively. Such variation is strongly associated with the uncertainty provided by the increase of conduction losses ranging between 40%~80% beyond the avalanche frequency.

Генерация шума в одночастотном генераторе на лавинно-пролетном диоде миллиметрового диапазона длин волн под воздействием низкочастотного гармонического колебания

The investigation of effect of the low-frequency harmonic oscillation on the nourishment circuit of the 7mm wave region IMPATT diode oscillator was continued. In first time it was shown, that excitement of noise and the maximum height-frequency noise spectrum extension at a low-frequency oscillation amplitude increasing are connected with a transitory decreasing of the diode current lower the start current of height-frequency generation in the IMPATT diode oscillator.

Synchronization of pulsed and continuous-wave IMPATT oscillators in the millimeter wavelength range. Part 1. Generator designs and a generalized model of their external signal synchronization

Advances in the development of ultrahigh-frequency semiconductor electronics open wide opportunities for developing optimal schemes and designs of microwave power sources in the millimeter wavelength range providing high stability of the frequency and electromagnetic oscillation phase. Synchronized diode generators used in transmit/receive module for active phased array antennas, coherent low-power radar stations, etc. show great promise. The mode of external synchronization of semiconductor generators allows effectively implementing the task of creating output stages of the transmitters with high gain factor, low frequency noise and an output power level corresponding to the maximum power mode. This article presents the first of two parts of the study, which summarizes the results achieved so far in the development of synchronized oscillators based on impact ionization avalanche transit-time (IMPATT) diodes. The first part presents the electrodynamic designs of the oscillators, which are synchronized with an external source of microwave oscillations and contain a resonant oscillating system with a silicon IMPATT diode. The silicon two-drift IMPATT diode was chosen as an active element due to the fact that its use allows reaching significant levels of pulsed microwave power – an order of magnitude higher than those of the most well-known HEMT and pHEMT transistors in the millimeter wavelength range. It is shown that to reduce losses, the oscillating system should be made in the form of a radial resonator with a diode casing, which has distributed parameters. This eliminates the use of additional reactive inhomogeneities in the initial cross-section of the waveguide section of the generator. Due to the low quality factor of the resonant casing of the diode, the generalized quality factor of the microwave circuit takes the minimum value required to implement a stable generator synchronization process in the millimeter wavelength range. The second part of the work will be devoted to synchronized pulse generators with an output power of 20–150 W.

Synchronization of pulsed and continuous-wave IMPATT oscillators in the millimeter wavelength range. Part 2. Stabilizing microwave parameters of synchronized generators

This is the second part of the two-part article, which summarizes the state-of-the-art results in the development of synchronized oscillators based on IMPATT (IMPact ionization Avalanche Transit-Time) diodes. The first part of the paper presented the electrodynamic design of oscillators, which contain a resonant oscillatory system with silicon IMPATT diodes and are synchronized by an external source of microwave oscillations. The second part of the paper considers the methods for stabilizing the parameters of IMPATT oscillators, which make it possible to create coherent power sources in the millimeter wavelength range. The specifics of pulse generators lies in the change in frequency within the microwave pulse relative to the change in temperature, which leads to a change in the impedance of the diode and thus to a phase change with respect to the synchronizing signal. Phase modulation is reduced or completely eliminated (which is necessary to ensure the coherence of the microwave transmitter) by using current compensation, i.e., by using the control current pulse with a special shape. The study demonstrates the expediency of introducing additional heating of the semiconductor structure of the IMPATT diode, which allows the initial temperature of the IMPATT diode in the region of the leading edge of each pulse to remain virtually constant and independent of the ambient temperature. Using these methods on silicon double-drift IMPATT diodes allowed creating synchronized oscillators with high frequency stability and an output power level from 20 to 150 W, which have a high degree of coherence in the synchronization mode with an external signal. The paper also presents the designs and parameters of coherent microwave power sources in the short-wave part of the millimeter wavelength range using the nonlinear properties of the IMPATT diodes in the radio-pulse conversion mode. This mode makes it possible to provide the output power level of the signal at the n-th harmonic Pout ≈1/n, which significantly exceeds the achieved characteristics of the frequency multipliers with charge accumulation, where Pout ≈ 1/n2. The output power of such devices is achieved at the level of 50–20 mW in the 75–180 GHz frequency range with a frequency multiplication factor of 1–15.