A comprehensive density-of-states model for oxide semiconductor thin film transistors

Kadiyam Rajshekar,D Kannadassan

doi:10.1007/s10825-021-01783-8

Abstract

In this paper, a novel and comprehensive density-of-states model is presented to understand the origin of conductivity and the performance of p-type and n-type oxide semiconductor thin film transistors (TFTs). To validate the model, the simulated I–V characteristics are compared with measured results of p-type Cu2O and SnO and n-type SnO2 TFTs. It was observed that cation vacancies are responsible for hole conduction in p-type TFTs, while anion vacancies and/or metal interstitials are responsible for electron conduction in n-type TFTs. This was observed by assigning the cation vacancies to acceptor-like Gaussian states and anion vacancies and/or metal interstitials to donor-like Gaussian states. The characteristic slopes in conduction/valence band-tail states are due to disorders present in the oxide semiconductors. The model successfully delivers the physical insight and pathway to circuit simulation of large-scale integration of pixel circuits in active matrix liquid crystal display/active matrix organic light-emitting diodes.

Highlights

Oxides Semiconductor (OS) thin film transistors (TFTs) have emerged as an important technology in transparent electronics and opto-electronic display devices while comparing polySi and amorphous silicon TFTs [1]
OSs show remarkably high field-effect mobility, wide bandgap and high uniformity over larger areas [2]. These properties help in development of many high performance display technologies, such as active matrix LCDs (AMLCD) and active matrix OLEDs (AMOLED) [3]
It was found that cation vacancies were responsible for hole conduction in p-type TFTs, while anion vacancies and/or metal interstitial were responsible for electron conduction in n-type TFTs

Summary

Introduction

Oxides Semiconductor (OS) thin film transistors (TFTs) have emerged as an important technology in transparent electronics and opto-electronic display devices while comparing polySi and amorphous silicon TFTs [1]. OSs show remarkably high field-effect mobility, wide bandgap and high uniformity over larger areas [2] These properties help in development of many high performance display technologies, such as active matrix LCDs (AMLCD) and active matrix OLEDs (AMOLED) [3]. CMOS transistors result an improved switching characteristics with architectural simplicity which offers a logic voltage swing with > 85% of high output voltage [10] They demand an efficient p-type OSs for future high-speed and high-density displays. CAD based numerical simulation tools, such technology-CAD (TCAD), are often used to design and analyse the semiconductor device and circuits They use physical models to describe the carrier transport, reaction for external electrical signals and optical nature of semiconductor devices. This physical model of OS helps device engineers and industries to design and optimize the high performance transparent electronic circuits

Density of States for Oxide Semiconductor

Numerical simulation of OS TFTs

P-type Cu2O and SnO TFTs

N-type SnO2 TFTs

Conclusion