Charge trapping of Ge-nanocrystals embedded in TaZrOx dielectric films

Abstract

Ge-nanocrystals (NCs) were synthesized in amorphous TaZrO x by thermal annealing of cosputtered Ge-TaZrO x layers. Formation of spherical shaped Ge-NCs with small variation of size, areal density, and depth distribution was confirmed by high-resolution transmission electron microscopy. The charge storage characteristics of the Ge-NCs were investigated by capacitancevoltage and constant-capacity measurements using metal-insulator-semiconductor structures. Samples with Ge-NCs exhibit a maximum memory window of 5 V by sweeping the bias voltage from À7 V to 7 V and back. Below this maximum, the width of the memory window can be controlled by the bias voltage. The fitted slope of the memory window versus bias voltage characteristics is very close to 1 for samples with one layer Ge-NCs. A second layer Ge-NCs does not result in a second flat stair in the memory window characteristics. Constant-capacity measurements indicate charge storage in trapping centers at the interfaces between the Ge-NCs and the surrounding materials (amorphous matrix/tunneling oxide). Charge loss occurs by thermal detrapping and subsequent band-to-band tunneling. Reference samples without Ge-NCs do not show any memory window. V

Effect of Ge Content on the Formation of Ge Nanoclusters in Magnetron-Sputtered GeZrOx-Based Structures

“…Recently, the Ge-ncs embedded in ZrO 2 [10, 11] and TaZrO x [12] were investigated. However, for deeper understanding of the mechanism of the formation, growth, and crystallization of Ge-ncs in the ZrO 2 matrix, further investigations are required.…”

Size and Shape Controlled Semiconductor Nanocrystals Synthesized by RF‐Sputtering Techniques for Electronic and Optoelectronic Applications

“…More details about the sample preparation can be found in [15]. Optical characterization was conducted as described above on similar samples consisting of 10 period superlattices of TaZrO x and Ge/TaZrO x to improve the PL signal.…”

“…In order to investigate the crystallization and charge storage characteristics of Ge nanocrystals embedded in TaZrO x MIS capacitors were fabricated as described above. Reprinted with permission from [15], Copyright 2015, AIP Publishing LLC. Fig.…”

“…Fig. Reprinted with permission from [15], Copyright 2015, AIP Publishing LLC. 4b) and 4c) after annealing at 700 • C. The thermal treatment leads to a phase separation of the co-sputtered Ge-TaZrO x composite layers (storage layers) resulting in the formation of spherically shaped Ge nanocrystals within amorphous TaZrO x .…”

“…Most applications of semiconductor nanocrystals require tight control of the nanocrystal shape, size, areal density and spatial distribution within the matrix. Attempts have been made to transfer this approach to other material systems, such as Ge nanocrystals embedded in insulating materials with high dielectric constants (high-k materials) like ZrO 2 [13,14] and TaZrO x [15]. Attempts have been made to transfer this approach to other material systems, such as Ge nanocrystals embedded in insulating materials with high dielectric constants (high-k materials) like ZrO 2 [13,14] and TaZrO x [15].…”