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

Describes a study of the DC and microwave characteristics of resonant-tunnelling 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 6.7*10⁴ A/cm². This is the highest value yet reported for either hot electron transistors or the quantum-effect devices.