Hydrogen density-of-states distribution in β-Ga2O3

N H Nickel,K Geilert

doi:10.1063/5.0030903

Abstract

Hydrogen bonding in β-Ga2O2 is investigated using hydrogen effusion measurements. The samples were grown by plasma-assisted pulsed laser deposition. With increasing deposition temperature, the total H concentration decreases from 8.1 × 1019 to 9.2 × 1018 cm−3. The dependence of the hydrogen chemical potential, μH, on the H concentration is derived from the effusion spectra and subsequently used to determine the H density-of-states distribution. β-Ga2O2 deposited at Tdep ≤ 723 K exhibits a needle-like peak in the H density-of-states distribution at ≈1.8 eV below the H transport states. With increasing Tdep, the H density-of-states changes and two broad peaks emerge that are located at ≈1.7 and 2.4 eV below the H transport states for Tdep ≥ 873 K.

Highlights

For a long time, it was believed that the main property of hydrogen is its ability to passivate localized defects in semiconductors
The dependence of the hydrogen chemical potential, μH, on the H concentration is derived from the effusion spectra and subsequently used to determine the H density-of-states distribution. β-Ga2O2 deposited at Tdep ≤ 723 K exhibits a needle-like peak in the H density-of-states distribution at ≈1.8 eV below the H transport states
As Tdep increases, pinning of the H chemical potential becomes less pronounced and disappears for specimens grown at Tdep ≥ 748 K

Summary

Introduction

It was believed that the main property of hydrogen is its ability to passivate localized defects in semiconductors. The properties of hydrogen comprise the compensation and neutralization of impurities and intentionally incorporated dopants, the formation of extended structural defects, and the formation of donor or acceptor states that influence the Fermi energy.. For β-Ga2O3, this unintentional doping effect has been attributed to the presence of either interstitial (Hi) or substitutional hydrogen at an oxygen site (HO). According to ab initio calculations, both centers act as shallow donors.. According to ab initio calculations, both centers act as shallow donors.3 This theoretical prediction was corroborated by muon spin relaxation measurements.. Infrared absorption measurements showed that the free-carrier absorption increases upon annealing of β-Ga2O3 in H2 atmosphere. The source of the additional charge carriers was related to the formation of shallow H donor complexes.

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Discussion

Conclusion