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Pitfalls of Using Pressure to Assign the Luminescence of Large‐Lattice‐Relaxation Defects
Author(s) -
Iota V.,
Weinstein B. A.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199901)211:1<91::aid-pssb91>3.0.co;2-m
Subject(s) - photoluminescence , vacancy defect , doping , materials science , band gap , lattice (music) , stokes shift , luminescence , acceptor , condensed matter physics , excitation , semiconductor , relaxation (psychology) , thermal , molecular physics , optoelectronics , chemistry , physics , thermodynamics , psychology , social psychology , quantum mechanics , acoustics
Deep defects are often assumed to be insensitive to applied pressure because of their localized character. However, in recent photoluminescence (PL) experiments, several deep acceptor bands in ZnSe were found to shift with pressure substantially faster than the ZnSe bandgap. This shows that the optical (viz., PL) levels of these acceptors become more shallow under compression, a result that, if also true for the thermal defect levels, is important for p‐type doping problems in II–VI semiconductors. We report investigations of the C 3v ‐relaxed isolated Zn‐vacancy (V Zn ) in ZnSe that help to resolve these issues. High‐pressure PL and PL‐excitation (PLE) experiments and calculations are performed on this system. We find that the V Zn ‐related PL and PLE bands have pressure coefficients that are, respectively, larger and smaller than that of the ZnSe bandgap. Hence, the Stokes‐shift decreases with pressure. These results can not be understood without taking explicit account of lattice relaxation. We employ a defect‐molecule model with atomic wavefunctions to calculate semi‐empirical configuration‐coordinate diagrams for the V Zn defect as a function of pressure. We find that compression increases the Jahn‐Teller coupling, but not sufficiently to overcome lattice stiffening. Overall, the V Zn thermal level deepens, inhibiting p‐type doping.