Physics of fluorine plasma ion implantation for GaN normally-off HEMT technology

Abstract

We provide an overview on the underlying physical mechanisms associated with the fluorine plasma ion implantation technology that provides a robust approach to fabricating GaN normally-off transistors. The discussion is based on atomistic modeling and a series of experimental studies including thermal diffusion, positron annihilation spectroscopy, photoconductivity and electroluminescence.

Influence of epitaxy and gate deposition process on Ron resistance of AlGaN/GaN-on-Si HEMT

“…ICP processes, regardless of the additional Cl-based over etching of the AlGaN layer, lead to similar results. Such Rsh degradation observed for RIE and ICP etching is often related to fluorine etching impact on ns [2,3] or μ [4]. XPS analysis confirme in our case the presence of fluor at the surface of the AlGaN layer (Fig.…”

“…This can be explained by the expected fluorine implantation profile associated to such etching process [3][4][5] (Fig. 9), showing first a main Gaussian profile in the first 10nm and a second low level profile injecting fluorine as deep as 40nm.…”

Gate Stability of GaN-Based HEMTs with P-Type Gate

“…The high electron density in the two-dimensional electron gas (2DEG) is obtained thanks to the spontaneous and piezoelectric polarization of GaN, without the need for any doping; typically, GaN-based transistors are normally-on devices, with a negative threshold voltage. Several methods have been recently proposed for the fabrication of normally-off GaN-based transistors: the use of a deep gate recess, in combination with a metal-insulator-semiconductor (MIS) stack [4]; the implantation of fluorine ions under the gate [5], that results in a significant depletion of the channel; the use of a p-type gate material, such as p-AlGaN [6] or p-GaN [7], which shifts the conduction band upwards, thus resulting in the depletion of the channel for negative gate voltages. As an alternative to these strategies, it has been also proposed to develop special E-mode devices, integrating a normally-on GaN HEMT connected in cascode configuration to a normally-off silicon MOSFET (Metal Oxide Semiconductor Field Effect Transistor) in the same package [8].…”

Device physics towards high performance GaN-based power electronics

“…a) 沿(0001)晶向俯视氟离子在AlGaN/GaN异质结构中的3种可能位置; (b) 氟离子从位置I, S(III)和S(V)移动到最近的 间隙位置I所克服的势能. Al0.25Ga0.75N与其下GaN晶格匹配, 处于应变状态[4] …”