Formation mechanism of gold-based and gold-free ohmic contacts to AlGaN/GaN heterostructure field effect transistors

TY - JOUR

T1 - Formation mechanism of gold-based and gold-free ohmic contacts to AlGaN/GaN heterostructure field effect transistors

AU - Shriki, A.

AU - Winter, R.

AU - Calahorra, Y.

AU - Kauffmann, Y.

AU - Ankonina, G.

AU - Eizenberg, M.

AU - Ritter, D.

N1 - Publisher Copyright: © 2017 Author(s).

PY - 2017/2/14

Y1 - 2017/2/14

N2 - To better understand the formation mechanism of ohmic contacts to GaN-based heterostructure field effect transistors, we have compared in detail Ti/Al/Ti/Au and Ti/Al/Ti/TiN contacts. Transmission electron microscopy and electron dispersive X-ray spectroscopy revealed that following anneal, TiN islands penetrated through the AlGaN barrier, as already well known, in the gold-based ohmic contacts but not in the gold-free contacts. We hence conclude that gold facilitates the formation of the TiN islands and propose that the role of gold is extraction of gallium from the semiconductor, providing a gallium depleted region for TiN island formation. For the case of the gold-free contacts, a 8 nm thick semi continuous TiN layer was formed following 900 °C anneal. A 2 nm thick TiN layer was observed in the as deposited samples and remained intact after anneal up to 825 °C. The different ohmic contact formation mechanism of gold-based and gold-free contacts is also manifested by our finding that a discontinuous AlN nitride spacer layer between the barrier and the bulk may lead to non-uniformity in contact behavior across the wafer in the case of gold-free contacts. For gold-based contacts, ohmic contact behavior was uniform across the wafer.

AB - To better understand the formation mechanism of ohmic contacts to GaN-based heterostructure field effect transistors, we have compared in detail Ti/Al/Ti/Au and Ti/Al/Ti/TiN contacts. Transmission electron microscopy and electron dispersive X-ray spectroscopy revealed that following anneal, TiN islands penetrated through the AlGaN barrier, as already well known, in the gold-based ohmic contacts but not in the gold-free contacts. We hence conclude that gold facilitates the formation of the TiN islands and propose that the role of gold is extraction of gallium from the semiconductor, providing a gallium depleted region for TiN island formation. For the case of the gold-free contacts, a 8 nm thick semi continuous TiN layer was formed following 900 °C anneal. A 2 nm thick TiN layer was observed in the as deposited samples and remained intact after anneal up to 825 °C. The different ohmic contact formation mechanism of gold-based and gold-free contacts is also manifested by our finding that a discontinuous AlN nitride spacer layer between the barrier and the bulk may lead to non-uniformity in contact behavior across the wafer in the case of gold-free contacts. For gold-based contacts, ohmic contact behavior was uniform across the wafer.

UR - http://www.scopus.com/inward/record.url?scp=85012103893&partnerID=8YFLogxK

U2 - 10.1063/1.4975473

DO - 10.1063/1.4975473

M3 - 文章

AN - SCOPUS:85012103893

SN - 0021-8979

VL - 121

JO - Journal of Applied Physics

JF - Journal of Applied Physics

IS - 6

M1 - 065301

ER -