Experimental analysis of resonant-tunneling hot-electron transistors operated at room temperature

The fabrication of AlAs/InGaAs resonant-tunneling hot-electron transistors (RHETs) operating at room temperature is reported. The device used for this study had a resonant-tunneling barrier consisting of a 26.4-Å InGaAs layer sandwiched by two 23.7-Å AlAs layers and a collector barrier of 2000-Å In_0.52Al_0.48As. These were grown on a semi-insulating InP substrate by MBE (molecular-beam epitaxy). The resonant-tunneling barrier exhibited negative differential resistance at room temperature, while the collector barrier was a good electrical isolator at room temperature. The collector current and base current were measured at room temperature as functions of base-emitter voltage with a constant 3 V on the collector in the common-emitter configuration. The current gain (and the differential current gain) increased with the base-emitter voltage, peaking at 0.64 V (0.56 V). As the base emitter voltage increased further, the current gain decreased. This is attributed to the intervalley scattering of electrons from the Γ-valley to the L-valleys in the InGaAs base. The scattering parameters of the RHET were measured from 0.2 to 20.2 GHz using the collector current density as a parameter and analyzed using an equivalent RHET circuit. The high-frequency capacitance and conductance of the resonant-tunneling-barrier were determined to be 93.0 fF and 1.98 mS/μm², respectively, at a collector current density of 3.3×10⁴ A/cm². The resonant-tunneling-barrier response time was 1.56 ps