Negative effective mass mechanism of negative differential drift velocity and terahertz generation

The negative-differential-drift-velocity instability, which forms the basis of Gunn high-frequency generators, can originate from Ridley-Watkins-Hilsum or negative effective mass (NEM) mechanisms. The first mechanism is dissipative by nature. The second is mainly drift-related. Therefore, the second mechanism promises to be more effective. We show the existence of stationary oscillatory regimes in the ballistic NEM p⁺p p⁺-diodes, which have a base in the form of a periodic system of parallel p-type quantum-well channels with base length up to 30 nm. An oscillation frequency, which depends on the base length, doping, and spatial period, as well as loads and voltage across the diode, ranges from ≤ 1 to 5 THz. We propose an additional combined quantum GaAs-AlGaAs-heterostructure, which can be overgrown on a cleaved edge of a specially grown wafer. This structure is intended to obtain electron dispersion relations with NEM sections in the useful energy range of 0.1-0.25 eV.