Investigation of Ti/Al/Ni/Au ohmic contacts for AlScN/GaN HEMTs
Abstract
The high bandgap of AlScN makes it difficult to achieve ohmic contacts with a low specific contact resistance (ρc) to AlScN/GaN heterostructures. High ρc increases the on-resistance of the high-electron-mobility transistor fabricated from these heterostructures and reduces the achievable current densities. This work presents an ohmic recess process and Ti/Al/Ni/Au metallizations with a ρc of 8.83×10−5 Ω cm2 after annealing at 900 °C. Interestingly, time-of-flight secondary ion mass spectrometry reveals that out-diffusion of Sc from the barrier to the metal surface occurs at anneal temperatures above 700 °C. While this structural metamorphosis does not show a strong impact on ρc, it leads to an increase in the on-resistance and gate leakage currents, as well as to a decrease in the maximum drain current of HEMTs. At an anneal temperature of 600 °C, no thermal degradation was observed and ρc as low as 13.4×10−5 Ωcm2 are achieved.
Article Details
Journal Info
Journal of Applied Physics
American Institute of Physics
Authors (10)
Isabel Streicher
Fraunhofer Institute for Applied Solid State Physics IAF 2 , Tullastrasse 72, 79108 Freiburg,
Simone Milazzo
Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM) 1 , Strada VIII n. 5-Zona Industriale, 95121 Catania,
Patrik Straňák
Fraunhofer Institute for Applied Solid State Physics IAF , 79108 Freiburg,
Lutz Kirste
Fraunhofer Institute for Applied Solid State Physics IAF , 79108 Freiburg,
Teresa Duarte
Fraunhofer Institute for Applied Solid State Physics IAF , 79108 Freiburg,
Salvatore Di Franco
Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM) 1 , Strada VIII n. 5-Zona Industriale, 95121 Catania,
Valerio Votadoro
Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM) 1 , Strada VIII n. 5-Zona Industriale, 95121 Catania,
Stefano Leone
Fraunhofer Institute for Applied Solid State Physics IAF , 79108 Freiburg,
Giuseppe Greco
Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM) 1 , Strada VIII n. 5-Zona Industriale, 95121 Catania,
Fabrizio Roccaforte
Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM) 1 , Strada VIII n. 5-Zona Industriale, 95121 Catania,