Noise characteristics of GaN-based IMPATTs
ABSTRACT The potential of noise characteristics of Wz-phase and Znb-phase
GaN IMPATTs is investigated and compared to Si and GaAs-based IMPATTs at
D-band. The noise of GaN-based IMPATTs is found to be higher than that
of GaAs-based IMPATTs but equivalent to Si-based IMPATTs. For increased
operation temperature, the noise is found to decrease
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ABSTRACT: The properties and performance of p + pnn + III-V semiconductor, viz., Indium Phosphide (InP) and Wurtzite phase of Gallium Nitride (Wz-GaN or α-GaN) based DDR Impatt diodes at Terahertz (THz) frequency has been investigated for optimum bias current density through modeling and simulation technique. A double iterative computer method based on drift-diffusion model has been used to study their performance. The bias current density is optimized with respect to maximum conversion efficiency and device negative resistance. The simulation studies reveal that these devices are potential sources for generating high RF power. The DC-to-RF conversion efficiency for InP DDR Impatt diode is found to be 18.38% at 0.3 THz and 13.18% at 0.5 THz at an optimum bias current density of 8.0 x 10 8 A/m 2 and 1.6 x 10 9 A/m 2 respectively. The same for α-GaN DDR Impatt diode is found to be 15.47% at 0.3 THz and 15.14% at 0.5 THz at an optimum bias current density of 0.5 x 10 7 A/m 2 and 1.1 x 10 8 A/m 2 respectively. The RF output power in case of DDR Impatt diode based on InP is found to be 2.81 W at 0.3 THz and 1.77 W at 0.5 THz while that in case of α-GaN DDR Impatt is 6.23 W at 0.3 THz and 9.34 W at 0.5 THz. The extensive simulation results reveal that Impatt diode based on α-GaN gives better performance in terms of efficiency and output power. The design results and the proposed experimental methodologies presented in this paper will be helpful to realize InP and α-GaN IMPATT oscillators for Terahertz communication.
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ABSTRACT: The mm-wave as well as noise properties of IMPATT diodes for the D-band are efficiently determined, with 4H-SiC and wurtzite type GaN as base materials, using advanced computer simulation techniques developed by the authors. The breakdown voltage (180 V) and efficiency (14.7%) is higher in case of 4H-SiC as compared to wz-GaN based diode having the breakdown voltage (153 V) and efficiency (13.7%). The study indicates that 4H-SiC IMPATT diode is capable of generating high RF power density of about 8.383×10 10 W/m 2 as compared to GaN IMPATT diode that is capable to develop the power density 6.847×10 10 W/m 2 for the same frequency of operation. It is also observed that wz-GaN exhibits better noise behavior 7.42×10 -16 V 2 ·s than SiC (5.16×10 -15 V 2 ·s) for IMPATT operation at 140 GHz. A tradeoff between the power output and noise from the device reveals that wz-GaN would be a suitable base material for high power application of IMPATT diode with moderate noise.
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ABSTRACT: The frequency chirping effect under optically illumination of Wurtzite phase of Gallium Nitride (Wz-GaN or α-GaN) based DDR Impatt diodes at 300 GHz or 0.3 Terahertz (THz) has been investigated. Top Mounted (TM) and Flip Chip (FC) structures are chosen and the composition of photocurrent is altered by shining light on the p + side and n + side of the device through optical windows. A double iterative computer simulation method based on drift-diffusion model has been used to study the small signal performance and subsequent modification of the small signal parameters owing to optical illumination. The role of leakage current in controlling the dynamic properties is studied by varying the current multiplication factors for electrons (Mn) and for holes (Mp). The simulation studies reveal that these devices are potential sources for generating high power at Terahertz domain. The conversion efficiency is found to be 15.47% at 0.3 THz at an optimum bias current density of 0.5 x 10 8 A/m 2 . The output power obtained is 6.23 W at 0.3 THz. The optical illumination reveals that a lowering of Mp causes more upward shift in frequency than a corresponding lowering of Mn. The frequency chirping in α-GaN Impatt is of the order of few GHz. The design results thus indicate the high photo-sensitiveness of α-GaN Impatts at Terahertz domain.