Eu-assisted enhancement of photoresponse in MBE-grown CdO/Si photodetectors

TL;DR

This study demonstrates that europium doping in CdO/Si photodetectors enhances their photoresponse and rectification properties, offering a promising approach for zero-power optoelectronic devices.

Contribution

It introduces Eu doping as a method to improve the performance of MBE-grown CdO/Si photodetectors, with detailed analysis of structural, vibrational, and electrical effects.

Findings

Eu doping increases rectifying factor and responsivity.

Eu incorporation alters vibrational properties of CdO.

Photodetectors operate effectively without external bias in 450-1150 nm range.

Abstract

Doping cadmium oxide with rare earth (RE) elements is a way to control the band gap and enhance carrier concentration and mobility. This work presents how one of REs, europium, impacts performance of CdO/Si diode. The samples were grown using plasma-assisted molecular beam epitaxy. Doping level was modified by changing the temperature of the effusion cell with Eu and therefore flux of Eu particles. Different dopant concentrations were confirmed by secondary ion mass spectrometry. Atomic force microscopy images revealed a grain-like surface structure of the samples with grain size increasing after rapid thermal processing (RTP). Raman spectroscopy showed that introducing Eu changes vibrational properties of CdO through intraionic anharmonicity reduction. Kelvin probe method revealed upward band bending caused by oxygen adsorption during RTP. Electrical measurements confirmed that rectifying junctions were manufactured and that they are able to produce photocurrent in the spectral range of 450-1150 nm without external voltage bias. Introducing Eu into CdO was found to increase e.g. rectifying factor and responsivity. The results show that doping CdO with Eu is a way to enhance performance of the presented zero-power-consumption photodetectors, making it a promising material for future applications in optoelectronics.