Effect of Dislocations on Local Transconductance in AlGaN/GaN Heterostructures as Imaged by Scanning Gate Microscopy

The spatial variation of transconductance in AlGaN/GaN heterostructures was mapped using the conducting tip of an atomic force microscope to locally modulate the two-dimensional electron gas (2DEG) while monitoring the change in the drain current as a function of tip position. A spatial resolution of 100 nm was obtained. 

This technique enables us to investigate the role of defects in transistor device performance. In particular, when biased near the depletion of the 2DEG, the transconductance map displays a cell structure, with low signal regions correlating with the positions of negatively charged threading dislocations.