Physical Modeling of Asymmetric Spacers Resonant Tunneling Diodes (RTDs)

The Resonant Tunneling Diode (RTD) is one of the most promising candidates for room temperature generation of terahertz (THz) radiation. Therefore, many attempts have been reported to increase the oscillation frequency beyond 1 THz either by reducing the mesa area or by thickening the collector spacer layer. Reducing the mesa area would reduce the Negative Differential Conductance (NDC), while increasing the thickness of the collector spacer layer would lead to an increase in the peak voltage value and increasing the emitter spacer thickness would increase the oscillation frequency while maintaining low peak voltage value. This work presents the physical modelling of asymmetric spacer resonant tunneling diodes (RTDs) to increase the oscillation frequency while still maintaining a low peak voltage, high NDC, and high output power. Different thicknesses of emitter spacer layer (7.5 nm and 10 nm) are simulated with varying thicknesses of the quantum well (3.5 nm, 3nm, and 2.5 nm) to study their effects on the DC and RF characteristics of the RTDs. Increasing the Indium concentration in the quantum well region has improved the oscillation frequency while maintaining a low peak voltage.