High quality GaAs-based resonant tunneling diodes for high frequency device applications

The influence of the barrier thickness (L_B) and the spacer length (L_S) on the current/voltage behavior of AlAs/GaAs/AlAs resonant tunneling diodes (RTDs) to achieve a high peak current density (J_p) and a low valley current density (J_V) for device applications at room temperature was studied. The samples were grown by molecular beam epitaxy. With increasing L_B in the range between 3 monolayers (ML) and 6 ML a drastic increase of the peak-to-valley current ratio (J_P/J_V) up to a maximum value of 5 (12) at 300 K (77 K) for L_B=6 ML is observed. Simultaneously, J_p decreases exponentially with thicker barriers. A maximum available current density in the negative-differential-resistance region of ΔJ=J_p-J_V=165 kA/cm² at 300 K is achieved for 4 ML thick AlAs barriers. No influence of the emitter spacer length variation on J_p for L_S>10 nm was found. However, for l _S<10 nm J_p increases with decreasing L_S (maximum improvement of 60% for L _S=0.5 nm). The PVR can be significantly improved by using a pseudomorphic InGaAs prewell layer for carrier injection