Non-alloyed, refractory metal contact optimization with shallow implantations of zinc and magnesium

• Published in: Thin solid films pp. 496 - 500
• Main Authors: Lovejoy, M L, Zolper, J C, Sherwin, M E, Baca, A G, Shul, R J, Rieger, D J, Klem, J F
• Format: Journal Article
• Language: English
• Published: 25.04.1994
• ISSN: 0040-6090

Refractory metal contacts to GaAs show great promise for stability during high temperature processing and for high reliability. In this paper, a study of sputtered tungsten and W-Si contacts to ion-implanted p-GaAs with both Zn and Mg implatnations is reported. This study focused on refractory contacts to shallow implanted contact layers that are suitable for devices such as junction field effect transistors and heterojunction bipolar transistors. The very different energy loss mechanisms of Zn and Mg ions result in different levels of implant damage, which is studied by varying the annealing temperatures and measuring the effects on contact and sheet resistances with the transmission line method. For the fabrication schemes investigated, the specific contact resistivity vs. annealing temperature values with implant doses from 1x10 exp 14 -5x10 exp 15 cm exp -2 are found to vary from non-ohmic to 10 exp -7 Omega cm exp 2 . Low resistance contacts to shallow ( < 800A) implanted layers are achieved.