Contents I. Introduction
Indium gallium zinc oxide (IGZO) has emerged as a promising candidate for future semiconductor devices owing to its high mobility, extremely low off-current and feasibility for 3D stackable DRAM configurations [1], [2]. In particular, crystalline IGZO (c-IGZO), which is crystalline in the c-axis but has randomly positioned cations in the perpendicular a-b planes, exhibits a unique electrical characteristic of mobility enhancement with the increase in carrier density [3]. Previous studies have attempted to model this unusual electrical property focusing on the cation disorder as the dominant scattering mechanism, but they were limited to the In:Ga:Zn = 1: 1: 1 structure considering only Zn and Ga atoms, or showed an order of magnitude difference in mobility compared to experimental data [4], [5]. Moreover, these studies applied the semiclassical Fermi's golden rule to a single disorder without disorder-to-disorder interaction, whereas in actual c- IGZO structures, the cation disorder scattering rate depends on the complex interplay between the randomly distributed cation disorders. In this work, we utilize a density functional theory (DFT) based method to calculate the cation disorder limited mobility for various c-IGZO compositions. The distribution of cation disorders is captured by atomic-level random cation pair switching within the DFT -generated structure. Multiple cation configurations are sampled to obtain the statistically averaged scattering effect for a given disorder density. Using DFT, IGZO structures with composition ratios of In: Ga: Zn = 1:1:1,1:1:2,7:5:6, and 4:2:3 are generated, and the corresponding cation disorder limited mobilities are calculated.
Schematic of the simulation flow for calculating the cation disorder limited mobility of c-IGZO.
