Fabrication and performance of InAs-based heterojunction bipolar transistors

InAs-based heterojunction bipolar transistors (HBTs) have great potential for applications requiring high speed and low power integrated circuits. Significant advantages of the InAs material properties over those of InGaAs and GaAs have motivated recent research into InAs-based HBTs. The advantages of InAs include a low bandgap, low electron effective mass, high peak velocity and high electron mobility. InAs/InAsP and InAs/InAlAs SHBT and DHBTs have been grown on both InAs and InP substrates. Initial results from InAsP/InAs HBTs grown on InAs and transferred to sapphire substrates show comparable performance to the well established InGaAs/InAlAs HBT. An Ft of 181 GHz has been measured at a collector-emitter voltage of 0.6 V and collector current of 7.6 mA. for 1×3 μm² sized emitter devices. Divide-by-16 circuits have been fabricated to demonstrate the basic building blocks for digital ICs.