Evidence for oxygen being a dominant shallow acceptor in p-type CuI

P Storm,S Gierth,M Lorenz,H Von Wenckstern,S Selle,M Grundmann,M S Bar

doi:10.1063/5.0047723

Abstract

For every semiconducting material, the long-term stability of thin film characteristics is a crucial necessity for device applications. This is particularly true for the p-type semiconductor CuI, where the thin film properties are especially sensitive to environmental influences and motivate the application of capping materials. Utilizing pulsed laser deposition (PLD) and Al2O3 cappings, we performed systematic studies on the N2/O2 partial pressure during growth and the effect of layer thickness. Our results suggest that oxygen, acting as an acceptor, and its diffusion through Al2O3 and CuI dominate the conductivity of PLD grown CuI thin films. The diffusion process of atmospheric oxygen into CuI was traced with 18O-isotopes. Additionally, the transparency and morphology of CuI films are also affected by the oxygen supply during capping growth. These results challenge the currently accepted idea that intrinsic, and not extrinsic, effects determine the conductivity of CuI thin films.

Highlights

In search of a p-type material that unites suitable electrical properties with a high degree of transparency as required for transparent bipolar transistor circuits in conjunction with unipolar ntype semiconductors such as ZnO or Ga2O3 or high-performance thin film transistors, copper iodide (CuI) emerged as a promising material
This is true for the p-type semiconductor CuI, where the thin film properties are especially sensitive to environmental influences and motivate the application of capping materials
Our results suggest that oxygen, acting as an acceptor, and its diffusion through Al2O3 and CuI dominate the conductivity of pulsed laser deposition (PLD) grown CuI thin films

Summary

INTRODUCTION

In search of a p-type material that unites suitable electrical properties with a high degree of transparency as required for transparent bipolar transistor circuits in conjunction with unipolar ntype semiconductors such as ZnO or Ga2O3 or high-performance thin film transistors, copper iodide (CuI) emerged as a promising material. For thin films grown by pulsed laser deposition, the carrier density could be varied between 1019 and 5 × 1016 cm−3 via the temperature during growth, while a change in the copper to iodine ratio was not observed. To gain a deeper understanding concerning the underlying mechanisms, we performed further investigations on the time-dependent electrical behavior of PLD grown CuI in dependence on growth parameters of the capping and the CuI itself. These results are compared to theoretical models, and the general impact of oxygen concerning the thin film properties of CuI was investigated

EXPERIMENTAL METHODS

OXYGEN DIFFUSION DYNAMICS

INTENTIONAL OXYGEN DOPING OF CUI

EFFECTS ON TRANSMITTANCE AND MORPHOLOGY

VIII. CONCLUSION