Impact ionization in InAs/AlSb field effect transistors

Field effect transistors (FETs) made from InAs/AlSb quantum wells have demonstrated excellent microwave performance ( fi = 93Ghz for a 0.5/spl mu/m gate length). However, a serious fundamental problem has plagued even our best InAs/A1Sb devices (and others reported in the literature): almost all devices show very poor drain I-V characteristics, with undesirably high drain conductances that increase rapidly with increasing drain voltage, leading to a pronounced turnup at very low voltages. The purpose of the present work is to demonstrate that the enhancement in drain conductance is caused by a feedback mechanism initiated by holes generated during the impact ionization of hot electrons in the InAs channel.