Direct measurement of defect and dopant abruptness at high electron mobility ZnO homojunctions
Abstract
Due to a strong Fermi-level mismatch, about 10% of the electrons in a 5-nm-thick highly Ga-doped ZnO (GZO) layer grown by molecular beam epitaxy at 250 °C on an undoped ZnO buffer layer transfer to the ZnO (Debye leakage), causing the measured Hall-effect mobility (μH) of the GZO/ZnO combination to remarkably increase from 34 cm2/V s, in thick GZO, to 64 cm2/V s. From previous characterization of the GZO, it is known that ND = [Ga] = 1.04 × 1021 and NA = [VZn] = 1.03 × 1020 cm−3, where ND, NA, and [VZn] are the donor, acceptor, and Zn-vacancy concentrations, respectively. In the ZnO, ND = 3.04 × 1019 and NA = 8.10 × 1018 cm−3. Assuming the interface is abrupt, theory predicts μH = 61 cm2/V s, with no adjustable parameters. The assumption of abruptness in [Ga] and [VZn] profiles is confirmed directly with a differential form of depth-resolved cathodoluminescence spectroscopy coupled with X-ray photoelectron spectroscopy. An anneal in Ar at 500 °C for 10 min somewhat broadens the profiles but causes no appreciable degradation in μH and other electrical properties.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 03, 2016
- Source ID
- 10.1063/1.4963888
Entities
People
- Chen Yang
- D. C. Look
- E. R. Heller
- G. Faber
- Geoffrey M. Foster
- Leonard J Brillson
- Y.-f. Yao
Organizations
- Air Force Office of Scientific Research
- Air Force Research Laboratory
- National Science Foundation
- National Science and Technology Council
- National Taiwan University
- Ohio State University
- Wright State University