Tunneling current in HfO2 and Hf0.5Zr0.5O2-based ferroelectric tunnel junction

Abstract

Ferroelectric tunnel junctions (FTJs) have been intensively explored for future low power data storage and information processing applications. Among various ferroelectric (FE) materials studied, HfO2 and H0.5Zr0.5O2 (HZO) have the advantage of CMOS process compatibility. The validity of the simple effective mass approximation, for describing the tunneling process in these materials, is examined by computing the complex band structure from ab initio simulations. The results show that the simple effective mass approximation is insufficient to describe the tunneling current in HfO2 and HZO materials, and quantitative accurate descriptions of the complex band structures are indispensable for calculation of the tunneling current. A compact k · p Hamiltonian is parameterized to and validated by ab initio complex band structures, which provides a method for efficiently and accurately computing the tunneling current in HfO2 and HZO. The device characteristics of a metal/FE/metal structure and a metal/FE/semiconductor (M-F-S) structure are investigated by using the non-equilibrium Green's function formalism with the parameterized effective Hamiltonian. The result shows that the M-F-S structure offers a larger resistance window due to an extra barrier in the semiconductor region at off-state. A FTJ utilizing M-F-S structure is beneficial for memory design.

QuantumATK: an integrated platform of electronic and atomic-scale modelling tools

“…where n λq is the phonon occupation operator, and g λnn kk q the EPC constant from (29). QuantumATK offers two different methods for performing the q-integral in (32). In the first method, the delta functions in (35) are represented by Gaussians with a certain width, and we perform the discrete sum over q.…”

Ferroelectric HfO2 Tunnel Junction Memory With High TER and Multi-Level Operation Featuring Metal Replacement Process

“…Since then, there are reports on experiments and theories for FTJ using conventional FE materials [3]- [11]. Although there are several experimental reports on FTJ with FE-HfO 2 [12]- [19], however, design guideline and process issues [13] are not fully addressed yet.…”

Design Space Exploration of Ferroelectric Tunnel Junction Toward Crossbar Memories

“…T F E is the ferroelectric thickness. We calibrate the compact model to metal-HfZrO 2 (HZO)-Ge tunnel junction from [6] One unique property of the metal-HZO-Ge device structure is the tunneling barrier width modulation (BWM) caused by the semiconductor band bending at the interface. There is a depletion layer caused by screening charge in the semiconductor Fig.…”

“…There is a depletion layer caused by screening charge in the semiconductor Fig. 2: Impact of barrier height modulation (BHM) and barrier width modulation (BWM) on the compact model [30] for (a) conventional metal-HZO-metal junction and (b) novel metal-HZO-Ge structure comparing against the non-equilibrium green's function (NEGF) simulation data from [6] electrode at the off-state, which will lead to an extra tunneling barrier width [6]. To capture this effect, we assume the HZO's polarization remains the same for different thickness.…”

“…Another unique characteristic of the metal-HZO-Ge device structure is the asymmetric I-V behavior of the HRS between positive and negative applied voltage. Due to interface effects between the ferroelectric and Ge layer, electrons tunneling from the metal to the conduction band of Ge sees a thicker barrier than the electrons tunneling from Ge to metal [6]. This results in different TER ratios between positive and negative case.…”