Analysis of notch-δ-doped GaAs-based Gunn diodes

Abstract

The performances of GaAs-based Gunn diodes with notch-δ-doped structures are studied in this work. The δ-doped effect is analysed using Monte Carlo modelling in terms of temporal evolution of current density, electric field profile, electron energy, mean velocity and occupancy in the Γ and higher valleys. The presence of a δ-doped layer after the notch causes a significant increase in the harmonic current amplitude of the device, where the growth of the high field domain can be attributed to a slow electron track due to the well-known Gunn effect and an additional fast electron track which appears over a short time window when the domain is reaching the anode. An optimised GaAs notch-δ-doped structure with a 700 nm device length including a 100 nm notch and a 5 nm δ-doped layer can generate signals at a fundamental frequency of 262 GHz with a current harmonic amplitude of 29.4 × 107 A m−2, which is almost twice of that without a δ-doped layer. Its second and third harmonic signals are found to be substantial, reaching into the terahertz range of 512 GHz and 769 GHz.