Effects of Al Precursors on the Characteristics of Indium-Aluminum Oxide Semiconductor Grown by Plasma-Enhanced Atomic Layer Deposition

Aluminum-Doped Indium Oxide Electron Transport Layer Grown by Atomic Layer Deposition: Highly Efficient and Damage-Resistant Interconnection Solution for All-Perovskite Tandem Solar Cells with 25.46% Efficiency

In fabricating high-efficiency all-perovskite tandem solar cells (APTSCs) with a p-i-n configuration, the electron transport layer (ETL) plays a critical role in facilitating the transport of photogenerated electrons from the front cell to the recombination layer and protecting the front cell from damage during rear cell fabrication. This study introduces aluminum-doped In2O3 (AIO) films grown by atomic layer deposition (ALD) as a promising ETL for high-efficiency APTSCs. ALD-grown AIO films with an optimized Al concentration exhibit superior charge transport characteristics, excellent transparency, and damage-resistant barrier properties against solution infiltration compared with conventional SnO2 ETLs and undoped ALD In2O3. Using an ALD SnO2/3 at.% AIO bilayer as the electron transport layer, an efficiency of 18.33% is achieved from single-junction wide bandgap perovskite solar cells. Furthermore, the use of ALD SnO2/3 at.% AIO ETL enables the reliable fabrication of APTSCs with negligible solution damage to the front cell and minimized power loss. Consequently, APTSC employing the ALD AIO-based ETL exhibit an excellent photoconversion efficiency of 25.46%, outperforming APTSCs with the ALD SnO2 ETL.

Tailoring Subthreshold Swing in A-IGZO Thin-Film Transistors for Amoled Displays: Impact of Conversion Mechanism on Peald Deposition Sequences

Amorphous IGZO (a-IGZO) thin-film transistors (TFTs) are standard backplane electronics to power active-matrix organic light-emitting diode (AMOLED) televisions due to their high carrier mobility and negligible low leakage characteristics. Despite their advantages, limitations in color depth arise from a steep subthreshold swing (SS) (≤ 0.1 V/decade), necessitating costly external compensation for IGZO transistors. For mid-size mobile applications such as OLED tablets and notebooks, it is important to ensure controllable SS value (≥ 0.3 V/decade). In this study, a conversion mechanism during plasma-enhanced atomic layer deposition (PEALD) is proposed as a feasible route to control the SS. When a pulse of a diethylzinc (DEZn) precursor is exposed to the M2O3 (M = In or Ga) surface layer, partial conversion of the underlying M2O3 to ZnO is predicted on the basis of density function theory calculations. Notably, significant distinctions between In-Ga-Zn (Case I) and In-Zn-Ga (Case II) films are observed: Case II exhibits a lower growth rate and larger Ga/In ratio. Case II TFTs with a-IGZO (subcycle ratio of In:Ga:Zn = 3:1:1) show reasonable SS values (313 mV decade-1) and high mobility (µFE) of 29.3 cm2 Vs-1 (Case I: 84 mV decade-1 and 33.4 cm2 Vs-1). The rationale for Case II's reasonable SS values is discussed, attributing it to the plausible formation of In-Zn defects, supported by technology computer-aided design (TCAD) simulations.

Electric field effect on H f x T i y O 2 ( x + y ) clusters for applications in MOSFETs and DSSCs: a DFT study

CONTEXT

The structural, electronic, non-linear optical (NLO) and spectral properties ofHf  x  Ti  y  O 2 (  x  + y ) clusters with(  x  +  y  ≤ 6 ) have been studied under the influence of an external electric field using density functional theory (DFT). The effect of variation in the Hf:Ti ratio on different properties of clusters is investigated. The motivation to studyHf  x  Ti  y  O 2 (  x  + y ) clusters lies in the fact that HfTiO thin films have wide applications in various optoelectronic and photovoltaic devices. So, it will be interesting to study the effect of electric field onHf  x  Ti  y  O 2 (  x  + y ) clusters with the variation in the number of Hf, Ti and O atoms. It is observed that out of all the clusters,Hf 4 Ti 1 O 10 andHf 5 Ti 1 O 12 are the most stable clusters with high values of binding energy and HOMO-LUMO gap. The application of an external electric field on these most stable clusters distorts their geometry and their HOMO-LUMO gap decreases, dipole moment and polarizability increases as the electric field is increased from 0 a.u. to 340 x10 − 4 a.u. The applied electric field increases the polar character of clusters due to electron cloud deformation and hence, increases the reactivity of the clusters, thus making these clusters suitable for electrocatalytic reactions. The electric field controlled high values of dielectric constant makes these clusters suitable to be used in the oxide layer of metal oxide semiconductor field effect transistors (MOSFETs) with better capacitance. Under the effect of an electric field, the absorption peaks of UV-VIS spectra gets red-shifted. Due to the tuning of absorption spectra from ultraviolet to visible region,Hf  x  Ti  y  O 2 (  x  + y ) clusters can be thought of as a good replacement forTiO 2 in dye-sensitized solar cells (DSSCs).

METHODS

The computational study ofHf  x  Ti  y  O 2 (  x  + y ) clusters has been performed using DFT. For the ground state ofHf  x  Ti  y  O 2 (  x  + y ) clusters, the optimization and frequency calculations have been performed using hybrid B3LYP (Becke three-parameter exchange functional combined with Lee, Yang and Parr correlation functional) functional with LANL2DZ (Los Alamos National Laboratory effective core potentials with Double Zeta atomic set) basis set under hybrid-GGA (generalized gradient approximation). Optimization and frequency calculations have been performed in each case. The excited state calculations have been carried out within time-dependent DFT formalism for a total of 50 excited states. The computational chemistry software package Gaussian 16 along with its graphical interface Gaussview have been employed for the current study ofHf  x  Ti  y  O 2 (  x  + y ) clusters.

Ultra-thin gate insulator of atomic-layer-deposited AlOxand HfOxfor amorphous InGaZnO thin-film transistors

To strengthen the downscaling potential of top-gate amorphous oxide semiconductor (AOS) thin-film transistors (TFTs), the ultra-thin gate insulator (GI) was comparatively implemented using the atomic-layer-deposited (ALD) AlO_xand HfO_x. Both kinds of high-kGIs exhibit good insulating properties even with the physical thickness thinning to 4 nm. Compared to the amorphous indium-gallium-zinc oxide (a-IGZO) TFTs with 4 nm AlO_xGI, the 4 nm HfO_xenables a larger GI capacitance, while the HfO_x-gated TFT suffers higher gate leakage current and poorer subthreshold slope, respectively originating from the inherently small band offset and the highly defective interface between a-IGZO and HfO_x. Such imperfect a-IGZO/HfO_xinterface further causes noticeable positive bias stress instability. Both ALD AlO_xand HfO_xwere found to react with the underneath a-IGZO channel to generate the interface defects, such as metal interstitials and oxygen vacancies, while the ALD process of HfO_xgives rise to a more severe reduction of a-IGZO. Moreover, when such a defective interface is covered by the top gate, it cannot be readily restored using the conventional oxidizing post-treatments and thus desires the reduction-resistant pre-treatments of AOSs.

Near-Ideal Top-Gate Controllability of InGaZnO Thin-Film Transistors by Suppressing Interface Defects with an Ultrathin Atomic Layer Deposited Gate Insulator

An ultrathin atomic-layer-deposited (ALD) AlO_x gate insulator (GI) was implemented for self-aligned top-gate (SATG) amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). Although the 4.0-nm thick AlO_x exhibited ideal insulating properties, the interaction between ALD AlO_x and predeposited a-IGZO caused a relatively defective interface, thus giving rise to hysteresis and bias stress instabilities. As analyzed using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and the Hall measurement, the chemical reaction between the ALD precursor and a-IGZO is revealed. This was effectively prevented by preoxidizing a-IGZO with nitrous oxide (N₂O) plasma. With 4 nm-AlO_x GI and low-defect interfaces, high performance and stability were simultaneously achieved on SATG a-IGZO TFTs, including a near-ideal record-low subthreshold swing of 60.8 mV/dec, a low operation voltage below 0.4 V, a moderate mobility of 13.3 cm²/V·s, a low off-current below 10^-13 A, a large on/off ratio over 10⁹, and negligible threshold-voltage shifts less than 0.04 V against various bias-temperature stresses. This work clarifies the vital interfacial reaction between top-gate high-k dielectrics and amorphous oxide semiconductors (AOSs) and further provides a feasible way to remove this obstacle to downscaling SATG AOS TFTs.

Performance improvement of Hf0.45Zr0.55Oxferroelectric field effect transistor memory with ultrathin Al-O bonds-modified InOxchannels

Ferroelectric field effect transistor (FeFET) memories with hafnium zirconium oxide (HZO) ferroelectric gate dielectric and ultrathin InO_xchannel exhibit promising applicability in monolithic three-dimensional (M3D) integrated chips. However, the inferior stability of the devices severely limits their applications. In this work, we studied the effect of single cycle of atomic-layer-deposited Al-O bonds repeatedly embedded into an ultrathin InO_xchannel (∼2.8 nm) on the Hf_0.45Zr_0.55O_xFeFET memory performance. Compared to the pure InO_xchannel, three cycles of Al-O bonds modified InO_xchannel (IAO-3) generates a much larger memory window (i.e. drain current ratio between the programmed and erased devices) under the same program conditions (+5.5 V/500 ns), especially after post-annealing at 325 °C for 180 s in O₂(1238 versus 317). Meanwhile, the annealed IAO-3 FeFET memory also shows quite stable data retention up to 10⁴s, and much more robust program/erase stabilities till 10⁵cycles. This is because the modification of strong Al-O bonds stabilizes the oxygen vacancies and reduces the bulk trap density in the channel. Furthermore, it is indicated that the program and erase efficiencies increase gradually with reducing the channel length of the memory device. By demonstrating markedly improved performance of the HZO FeFET memory with the ultrathin IAO-3 channel, this work provides a promising device for M3D integratable logic and memory convergent systems.