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Detection of Optically Excited States in Wide‐Band‐Gap Semiconductors with Tunneling Spectroscopy
Author(s) -
Rohrer Gregory S.,
Bonnell Dawn A.,
French Roger H.
Publication year - 1990
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1990.tb06447.x
Subject(s) - photoexcitation , excited state , quantum tunnelling , semiconductor , band gap , charge carrier , spectroscopy , dopant , scanning tunneling spectroscopy , materials science , doping , atomic physics , chemistry , condensed matter physics , molecular physics , optoelectronics , physics , quantum mechanics
Tunneling spectroscopy has been used to detect the photoexcitation of charge carriers in the wide‐band‐gap semiconductors, ZnO and cubic SiC. Photoexcitation, which increases the charge carrier population and thus reduces the width of the depletion layer at the semiconductor surface, is detected as an enhancement in the tunnel current. Because the process is energy sensitive, valence‐to‐conduction band or defect charge transfer transitions may be selectively excited and detected by tunneling spectroscopy. Two types of transitions were detected which change the tunneling response; for cubic SiC valence‐to‐conduction band transitions were excited, while for Co 2+ ‐ and Mn 2+ ‐doped ZnO electron charge transfer transitions from the dopants to the conduction bands occur. The enhancement of the current was greater in air than under vacuum and more easily detected at small sample‐tip separations.