Role of ALD Al2O3 surface passivation on the performance of p-type Cu2O thin film transistors

TL;DR

This study demonstrates that ALD Al2O3 surface passivation significantly enhances p-type Cu2O thin film transistors by reducing trap states and improving switching characteristics through interface modification and field-effect passivation.

Contribution

It introduces a novel ALD Al2O3 passivation method for Cu2O TFTs, showing improved performance via interface engineering and surface chemistry control.

Findings

Enhanced TFT switching characteristics with Al2O3 passivation

Formation of CuAlO2 interfacial layer reduces trap states

Surface passivation decreases off-state leakage currents

Abstract

High-performance p-type oxide thin film transistors (TFTs) have great potential for many semiconductor applications. However, these devices typically suffer from low hole mobility and high off-state currents. We fabricated p-type TFTs with a phase-pure polycrystalline Cu2O semiconductor channel grown by atomic layer deposition (ALD). The TFT switching characteristics were improved by applying a thin ALD Al2O3 passivation layer on the Cu2O channel, followed by vacuum annealing at 300 C. Detailed characterisation by TEM-EDX and XPS shows that the surface of Cu2O is reduced following Al2O3 deposition and indicates the formation of 1-2 nm thick CuAlO2 interfacial layer. This, together with field-effect passivation caused by the high negative fixed charge of the ALD Al2O3, leads to an improvement in the TFT performance by reducing the density of deep trap states as well as by reducing the accumulation of electrons in the semiconducting layer in the device off-state.