Influence of surface defects on the characteristics of high electron mobility transistors grown by molecular-beam epitaxy

Surface defects on layers grown by molecular-beam epitaxy were classified, and their effect on high electron mobility transistor characteristics was studied. The defects originating from the Ga source consist of cores and hillocks. These defects had a strong influence only when their cores were located in the gate region. They decreased the transconductance and K value significantly and shifted the threshold voltage to the negative direction. This indicates the cores are highly conductive. The other defects, originating from substrate surface contamination, slightly decreased the K value and transconductance while increasing the deviation in the threshold voltage.