Numerical study of sub-millimeter Gunn oscillations in InP and GaN vertical diodes: Dependence on bias, doping, and length

Abstract

In this work, we report on Monte Carlo simulations of InP and GaN vertical Gunn diodes to optimize their oscillation frequency and DC to AC conversion efficiency. We show that equivalent operating conditions are achieved by the direct application of a sinusoidal AC voltage superimposed to the DC bias and by the simulation of the intrinsic device coupled with the consistent solution of a parallel RLC resonant circuit connected in series. InP diodes with active region about 1 µm offer a conversion efficiency up to 5.5 % for frequencies around 225 GHz. By virtue of the larger saturation velocity, for a given diode length, oscillation frequencies in GaN diodes are higher than for InP structures. Current oscillations at frequencies as high as 675 GHz, with 0.1 % efficiency, are predicted at the sixth generation band in a 0.9 µmlong GaN diode, corroborating the suitability of GaN to operate near the THz band. At the first generation band, structures with notch in general provide lower oscillation frequencies and efficiencies in comparison with the same structures without notch.However, a higher number of generation bands are originated in notched diodes, thus typically reaching larger frequencies. Self-heating effects reduce the performance, but in GaN diodes the efficiency is not significantly degraded.

The enhancement of the output characteristics in the GaN based multiple‐channel planar Gunn diode

“…This choice significantly simplifies the frequency performance assessment. The equivalence between the operation of a diode connected in series with a resonant circuit and the direct application of a signal consisting in the superposition of a sinusoidal AC component to the DC bias has been proved in previous articles . The DC‐to‐RF conversion efficiency is defined as η = − P RF / P DC , where P RF is the time‐average AC power, P DC is the dissipated DC by the Gunn diode.…”

Research on the origin of negative effect in uniform doping GaN-based Gunn diode under THz frequency

“…Recently, many efforts have been made to improve the efficiency, operating frequency, and output power of Gunn diodes, both in vertical and in planar [3][4][5]. What is more, the electron energy relaxation time in GaN is much smaller than that in traditional III-V materials such as GaAs [6,7].…”

Intermittency route to chaos and broadband high-frequency generation in semiconductor superlattice coupled to external resonator

“…In this case the resonator can be substituted by an equivalent lumped LRC circuit, which is characterized by frequency, f Q , and by quality factor, Q. Such a single-mode approximation, which allows us to significantly simplify analysis and simulation of extended electrodynamic systems, is often used in a wide spectrum of problems, examples of which include helix structures in TWT amplifiers [53,54], klystrons [55], and Gunn diodes coupled to an external resonator [56,57]. The current I (t) generated by the SL depends on voltage V sl applied to the device.…”