Enhancement in electrical properties of GaN heterostructure field‐effect transistor by Si atom deposition on AlGaN barrier surface

Abstract

This study demonstrates that deposition of Si atoms on AlGaN barrier surfaces in GaN heterostructure field‐effect transistors (HFETs) can modulate the electrical properties of the two‐dimensional electron gas (2DEG). The results of Hall measurements performed using the eddy current and four‐point van der Pauw methods showed that the sheet resistance of an AlGaN/GaN HFET sample without surface passivation increased from that of the unprocessed sample after post‐metallization annealing at 820 °C for ohmic contacts. In contrast, the sheet resistance of the Si‐deposited sample did not increase even after annealing. Furthermore, eddy current measurements for unprocessed wafers with and without Si deposition revealed that the sheet resistance can be reduced by depositing Si atoms, regardless of annealing. The effect of Si deposition on devices having a thin Al‐rich barrier layer was found to be significant. The deposition of Si atoms (2 nm) on the AlN barrier surface in an AlN/GaN HFET (AlN 2 nm) resulted in a remarkable decrease in the sheet resistance from 60356 to 388 Ω/sq. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Analytical modeling of AlGaN/AlN/GaN heterostructures including effects of distributed surface donor states

“…Presently, these fields are usually measured by sophisticated techniques such as contactless electro-reflectance 28 or kelvin probe spectroscopy. 29 Instead, the above model enables us to perform precise, analytical estimates of such important quantities based on more readily available experimental determination of qU b and n s . In Fig.…”