Impact ionization and transport in the InAlAs/n/sup +/-InP HFET

Abstract
-We have carried out an experimental study exploring both impact ionization and electron transport in InAlAs/n+-InP HFET’s. Our devices show no signature of impact ionization in the gate current, which remains below 17 p”m under typical bias conditions for L, = 0.8 pm devices (60 ties lower than for InAlASnnGaAs HEMT’s). The lack of impact ionization results in a drain-source breakdown voltage (BV’s) that increases as the device is turned on, displaying an off-state value of 10 V. Ad- ditionally, we find that the channel electron velocity approaches the InP saturation velocity of about lo7 cm/s (in devices with L, , the device well-suited to power applications demanding small IG, low gd, and high BVDS.