Luminescence of deep phosphorous and arsenic impurities in ZnSe at high pressure.

Abstract

High-pressure photoluminescence (PL) is reported for bulk and thin-film ZnSe containing ${10}^{18}$--${10}^{19}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ P and As acceptors using a cryogenic (4--300 K) diamond-anvil cell to 55 kbar. We focus on the deep PL bands in the red and green regions of the visible spectrum; the red emission bands (1-atm peaks at \ensuremath{\sim}6000 A in ZnSe:P and \ensuremath{\sim}7000 A in ZnSe:As) are thought to stem from ${\mathit{C}}_{3\mathit{v}}$-distorted acceptor sites. With increasing pressure in the range studied, the peak energies of all the deep bands approach but do not cross the ZnSe band gap. The average deformation potential of the valence edge relative to the P or As deep levels attributed to ${\mathit{C}}_{3\mathit{v}}$ sites is -1.2\ifmmode\pm\else\textpm\fi{}0.3 eV. The negative sign is confirmed by thermal quenching data at different pressures in ZnSe:P. These results imply that with pressure the valence edge shifts to higher energy, causing deep acceptor states to become less stable. We also observe under pressure strong transfer of oscillator strength from red to green emission, and several deep bands. However, since the shallow acceptor-bound exciton PL is not enhanced, we conclude that a deep-to-shallow transition has not occurred within the pressure range studied.