Effect of post-deposition treatment on electrical properties of solution-processed a-IGZO Schottky diodes

Veronika Ulianova,Yurii Didenko,Galo Torres Sevilla,Yaroslav E Romanyuk,Dmytro Tatarchuk,Ivan Shorubalko,Evgeniia Gilshtein,Sami Bolat

doi:10.1063/5.0005970

Abstract

The fabrication of solution-processed electronic devices based on amorphous In–Ga–Zn–O (a-IGZO) requires high-temperature post-deposition annealing to activate IGZO layers and minimize impurities. Deep-ultraviolet (DUV) treatment can reduce the post-deposition annealing temperature when manufacturing a-IGZO thin-film transistors. Here, we investigate the effect of thermal annealing and DUV treatment in a nitrogen and ozone atmosphere on the properties of vertical thin-film Pt–IGZO–Cu Schottky diodes based on spin-coated a-IGZO. The DUV treatment in nitrogen allowed reducing the process temperature to 200 °C. A defect-induced hysteresis was observed on the current–voltage characteristics of as-fabricated Schottky diodes. The values of rectification ratio and barrier height were higher and the values of ideality factor were lower upon the backward bias sweep. It is assumed that the hysteresis behavior is caused by the presence of trap states in the semiconductor layer or at the Schottky interface. A trap density of 108 cm−2 to 1011 cm−2 was deduced from the current–voltage characteristics. The defect-induced hysteresis effect could be suppressed by depositing an Al2O3 layer and applying an additional thermal treatment of the whole diode structure.

Highlights

Amorphous indium gallium zinc oxide (a-IGZO) is widely used as an active layer in integrated semiconductor devices due to high carrier mobility, high transparency in the visible range of the light spectrum, and simplicity of patterning.[3]
We investigate the effect of thermal annealing (TA) and DUV treatment on the properties of Pt–IGZO Schottky contacts based on the solution-processed a-IGZO thin film
The values of the series resistance Rs, saturation current Is, ideality factor n, Schottky barrier height Φb, and electron affinity of the IGZO χIGZO are obtained by fitting the linear part of measured I–V characteristics in forward and backward sweep directions based on the following equations: I = AA∗T2 ⋅ exp(−qφb/kT)[exp(q(V − IRs)/nkT) − 1], (1)

Summary

INTRODUCTION

Amorphous indium gallium zinc oxide (a-IGZO) is widely used as an active layer in integrated semiconductor devices (transistors,[1] diodes,[2] etc.) due to high carrier mobility, high transparency in the visible range of the light spectrum, and simplicity of patterning.[3]. Since the inkjet printing of a-IGZO was demonstrated,[8] most of the studies have focused on the optimization of the process and electrical properties of the transistors.[9,10] Fabrication of printed semiconductor devices such as transistors,[8,11] memristors,[12] and rectifiers[13] based on a-IGZO requires high-temperature postdeposition annealing at 450 ○C–700 ○C to remove organic ligand groups or polymer binders and minimize impurities and unnecessary carbon groups, which adversely affect device performance.[14,15]. We investigate the effect of thermal annealing (TA) and DUV treatment on the properties of Pt–IGZO Schottky contacts based on the solution-processed a-IGZO thin film. The DUV-assisted approach enables lowering the process temperature of Schottky diodes fabrication to 200 ○C. An additional low-temperature annealing treatment of the fabricated structures was found to suppress the hysteresis effect in current–voltage characteristics

EXPERIMENTAL

Electrical characteristics extraction

Estimation of the interface trap density

CHARACTERIZATION AFTER ADDITIONAL LOW-TEMPERATURE ANNEALING

Findings

CONCLUSIONS