# Electronic structure and transport in amorphous metal oxide and amorphous metal oxy-nitride semiconductors

## TL;DR

This study compares electronic structures and transport mechanisms in amorphous metal oxide and oxy-nitride semiconductors, revealing how orbital overlaps influence carrier mobility and providing insights for designing high-performance amorphous semiconductors.

## Contribution

It introduces a computational comparison of a-IGZO and a-ZnON, elucidating their electronic transport paths and correlating orbital overlap with carrier effective mass.

## Key findings

- a-ZnON has higher mobility due to Zn-4s orbital overlap
- Transport in a-IGZO involves mixed cation s-orbitals
- Orbital overlap integral correlates with effective mass

## Abstract

Recently amorphous oxide semiconductors (AOS) have gained commercial interest due to their low-temperature processability, high mobility and areal uniformity for display backplanes and other large area applications. A multi-cation amorphous oxide (a-IGZO) has been researched extensively and is now being used in commercial applications. It is proposed in the literature that overlapping In-5s orbitals form the conduction path and the carrier mobility is limited due to the presence of multiple cations which create a potential barrier for the electronic transport in a-IGZO semiconductors. A multi-anion approach towards amorphous semiconductors has been suggested to overcome this limitation and has been shown to achieve hall mobilities up to an order of magnitude higher compared to multi-cation amorphous semiconductors. In the present work, we compare the electronic structure and electronic transport in a multi-cation amorphous semiconductor, a-IGZO and a multi-anion amorphous semiconductor, a-ZnON using computational methods. Our results show that in a-IGZO, the carrier transport path is through the overlap of outer s-orbitals of mixed cations and in a-ZnON, the transport path is formed by the overlap of Zn-4s orbitals, which is the only type of metal cation present. We also show that for multi-component ionic amorphous semiconductors, electron transport can be explained in terms of orbital overlap integral which can be calculated from structural information and has a direct correlation with the carrier effective mass which is calculated using computationally expensive first principle DFT methods.