A study on the influence of local doping in atomic layer deposited Al:ZnO thin film transistors

Abstract

Local doping of Al:ZnO into a ZnO matrix was performed vertically at various positions in a thin film using atomic layer deposition, and its influence was investigated by analyzing thin film transistor (TFT) characteristics. The position specific dopant distribution in the films was confirmed by high resolution transmission electron microscopy. It was found that doping specific locations in the active channel layer of a TFT had a different impact on its electrical characteristics. When near the semiconductor/gate dielectric interface, doping had a significant impact on the mobility of the TFT devices, which showed a gradual recovery as the doped region was moved away from the interface. The original characteristics of the device were almost completely restored once the doped region was moved more than 15 nm away from the interface, and when moved further away the output characteristics portrayed a shift in threshold voltage while preserving all other electrical characteristics. Various doping concentrations were implemented in regions both near and far away from the interface to gain a better understanding of the phenomena. The experimental results given here imply that the geographical position of doping is as important as selecting a dopant material in the device optimization of TFTs.

Review of recent advances in flexible oxide semiconductor thin-film transistors

“…A number of reports about oxide TFTs based on ALD were recently published, which showed the comparable performance of such TFTs to those fabricated using the sputter or solution methods, such as the 20 cm 2 /Vs-ZnO TFT by Lin et al [60], the 13.4 cm 2 /Vs-ZnHfO TFT by Nayak et al [61], the 6 cm 2 /Vs-AZO TFT by Chung et al [62], etc. [57,58,63].…”

Simultaneous enhancement of carrier mobility and concentration via tailoring of Al-chemical states in Al-ZnO thin films

“…In particular, transparentconductive characteristics of AZO films depend on E g modulation by controlling dopants concentration and defects creation by O vacancies. 11 To enhance the transparentconductive characteristics, effect of growth conditions under spray pyrolysis, 12 magnetic field alignment process, 10 laser molecular beam epitaxy, 13 atomic layer deposition, 11,14 pulsed laser deposition, 15,16 chemical bath technique, 17 plasma based chemical vapor deposition, 18 RF sputtering, [19][20][21] and DC sputtering [22][23][24] have been utilized. Among these, plasma based sputtering techniques have the advantage for large area and fast deposition, but require substrate heating for good conductivity.…”

New development of atomic layer deposition: processes, methods and applications

“…More information on the influence of the composition of materials on devices and the effects of temperature transistors through the application of the ALD process can be found in the papers referenced [182][183][184][185][186][187][188][189][190][191][192][193].…”