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.

Defect Manipulation To Control ZnO Micro-/Nanowire-Metal Contacts

“…Figure b shows Cu Zn peak intensity for E B = 3.5 keV, corresponding to ∼80 nm excitation depth within the wire for different diameters. Based on a previous NBE-normalized calibration, near-surface V Zn densities are estimated to be ∼1 × 10 21 cm –3 . However, calibration of Cu Zn densities is not yet available.…”

Native Point Defect Measurement and Manipulation in ZnO Nanostructures

“…The defect intensities of this wire calibrated with Hall Effect measurements [54] show that defect intensities at Contact 1 are high enough to enable defect-assisted hopping conduction, whereas the lower densities at Contact 4 permit a Schottky barrier to form [18]. The narrow diameter Contact 5 coupled with n-type carrier compensation by V Zn acceptors increases the depletion width radially to pinch off free carrier transport under the contact.…”

Impact of Nd Doping on Electronic, Optical, and Magnetic Properties of ZnO: A GGA + U Study

“…In 2000, Dietl's research team found that manganese-doped ZnO and GaN can obtain room-temperature ferromagnetism according to their calculations [3] and predicted that transition metal-doped ZnO semiconductors are dilute magnetic semiconductors with room-temperature ferromagnetism, which laid the foundation for the research of oxidebased dilute magnetic semiconductors. ZnO, a semiconductor with high-exciton binding energy (60 eV) and wide bandgap (3.37 eV), is magnetic owing to intrinsic defects, as well as the doping effect of rare earth elements and 3d transition metals and other magnetic ions and shows significant application value in the fields of information storage and processing [4][5][6]. However, there are drawbacks, such as a low Curie temperature.…”