Extraction of the edge/areal components and path of the reverse gate leakage in a GaN HEMT from measurements

Abstract

Reverse gate leakage, I G, limits the reliability of gallium nitride high electron mobility transistors. We extract the components of I G flowing into the edge and area of the gate from the measured I G versus gate to source voltage, V GS, data of both low and high I G devices. The components are separated by analyzing the change in I G with gate length, L G. We estimate the short and long channel limits of L G for which the I G flows predominantly into the edge and area, respectively. Prior one-dimensional I G models based on the areal field are valid for simulating long channel devices. However, the I G of short channel devices should be modeled using the edge field, and can be reduced by techniques like field plate or high-k passivation which reduce the edge field. Also, we find the measured I G to be independent of the un-gated length, implying that I G flows via the channel rather than surface. Our work dispels any prior misperception of I G being area dominated irrespective of L G and gives the right direction for modeling and control of I G.