Molecular Beam Epitaxy Growth and Characterization of Germanium-Doped Cubic AlxGa1−xN

Loading...
Thumbnail Image
Date
2020
Volume
257
Issue
4
Journal
Physica status solidi : B, Basic research
Series Titel
Book Title
Publisher
Weinheim : Wiley-VCH
Link to publishers version
Abstract

In cubic (c-)GaN Ge has emerged as a promising alternative to Si for n-type doping, offering the advantage of slightly improved electrical properties. Herein, a study on Ge doping of the ternary alloy c-AlxGa1−xN is presented. Ge-doped c-AlxGa1−xN layers are grown by plasma-assisted molecular beam epitaxy. In two sample series, both the Al mole fraction x and the doping level are varied. The incorporation of Ge is verified by time-of-flight secondary ion mass spectrometry. Ge incorporation and donor concentrations rise exponentially with increasing Ge cell temperature. A maximum donor concentration of 1.4 × 1020 cm−3 is achieved. While the incorporation of Ge is almost independent of x, incorporation of O, which acts as an unintentional donor, increases for higher x. Dislocation densities start increasing when doping levels of around 3 × 1019 cm−3 are exceeded. Also photoluminescence intensities begin to drop at these high doping levels. Optical emission of layers with x > 0.25 is found to originate from a defect level 0.9 eV below the indirect bandgap, which is not related to Ge. In the investigated range 0 ≤ x ≤ 0.6, Ge is a suitable donor in c-AlxGa1−xN up to the low 1019 cm−3 range.

Description
Keywords
Collections
License
CC BY 4.0 Unported