121 GHz resonant-tunnelling hot electron transistors having new collector barrier structure

A study is described of the dc and microwave characteristics of resonant-tunneling hot electron transistors (RHETs) fabricated using a new i-InAlGaAs/i-GaAs collector barrier structure. The current gain at a low collector-base voltages was improved, enabling the RHETs to operate at low collector-emitter voltages and to decrease the transit time. A cutoff frequency f(T) of 121 GHz was achieved at a temperature below 77 K with an emitter current density of 67,000 A/sq cm. This is the highest value yet reported for either hot electron transistors or the quantum-effect devices.