2-7 June 2019
Simon Fraser University
America/Vancouver timezone
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Potential mapping in GaN nanowire p-n junctions via off-axis electron holography

3 Jun 2019, 14:00
15m
SCP 8445.2 (Simon Fraser University)

SCP 8445.2

Simon Fraser University

Oral Competition (Graduate Student) / Compétition orale (Étudiant(e) du 2e ou 3e cycle) Condensed Matter and Materials Physics / Physique de la matière condensée et matériaux (DCMMP-DPMCM) M2-11 Materials synthesis and characterization II (DCMMP) | Synthèse et caractérisation de matériaux II (DPMCM)

Speaker

Anitha Jose (Simon Fraser University)

Description

GaN nanowires (NWs) have been applied in devices including light emitting diodes (LEDs) photodetectors and laser diodes, but control of the dopant distribution has been a difficult task [1]. Also it is well known that polarization effects have an influence on device properties. A previous report on GaN NWs found an effect of strain on the charge distribution via off-axis electron holography EH [2]. We report the measurement of the electric potential and depletion width in GaN NW p-n junctions using EH which is carried out using transmission electron microscopy (TEM) [3]. Nanowire p-n junctions grown by Molecular Beam Epitaxy, with Mg and Si as the p and n-type dopants, had doping concentration of 5 x 1017 and 1 x 1019 cm3, respectively, based on planar growth calibrations. A high density of basal plane (0001) stacking faults was found to be present within the p-type side whereas the n-side was free of detectable defects. Also the diameter of the p–type segment of the wires was always larger and highly anisotropic compared to the more uniform diameter n-type side. Phase images and potential profiles, extracted from the EH measurements, showed both an effect of thickness and the presence of a junction. An average built-in voltage of 0.5 ± 0.1 V and depletion width of 80 ± 5 nm were measured which both indicate either a smaller carrier activation or reverse biasing from charging or polarization effects. Results from a variety of growth conditions and structures will be presented.
1. Wallentin, J et al. Doping of semiconductor nanowires. J. Mater. Res. 26, 2142 (2011).
2. Chen, X et al. Controlling charges distribution at the surface of a single GaN nanowire by in-situ strain. Prog. Nat. Sci. Mater. Int. 27, 430–434 (2017).
3. Darbandi, A et al. Direct Measurement of the Electrical Abruptness of a Nanowire p–n Junction. Nano Lett. 16, 3982–3988 (2016).

Primary author

Anitha Jose (Simon Fraser University)

Co-authors

Prof. Karen L. Kavanagh (SFU) Dr Sharif Sadaf (Advanced Electronics and Photonics, National Research Council Canada) Dr Haipeng Tang (Advanced Electronics and Photonics, National Research Council Canada)

Presentation Materials