Changes of electronic properties of p-GaN(0 0 0 1) surface after low-energy N+-ion bombardment
Abstract
The p-GaN(0 0 0 1) crystal with a relatively low acceptor concentration of 5 × 1016 cm-3 is used in these studies, which are carried out in situ under ultrahigh vacuum (UHV) by ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED). The p-GaN(0 0 0 1)-(1 × 1) surface is achieved by thermal cleaning. N+-ion bombardment by a 200 eV ion beam changes the surface stoichiometry, enriches it with nitrogen, and disorders it. Such modified surface layer inverts its semiconducting character from p- into n-type. The electron affinity for the already cleaned p-GaN surface and that just after bombardment shows a shift from 2.2 eV to 3.2 eV, as well as an increase of band bending at the vacuum/surface interface from 1.4 eV to 2.5 eV. Proper post-bombardment heating of the sample restores the initial atomic order of the modified layer, leaving its n-type semiconducting character unchanged. The results of the measurements are discussed based on two types of surface states concepts.
- Publication:
-
Applied Surface Science
- Pub Date:
- May 2018
- DOI:
- 10.1016/j.apsusc.2018.01.097
- Bibcode:
- 2018ApSS..440..547G
- Keywords:
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- Semiconductor;
- GaN;
- Vacuum/surface interface;
- Valence band;
- Photoelectron spectroscopy