Photoluminescence of Cu-Doped Gallium Arsenide

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Abstract
Photoluminescence measurements made at 20° and 77°K on Cu‐diffused GaAs are compared with Hall‐effect measurements on the same specimens. The level of the singly charged Cu acceptor lies 0.155 eV (20°K) above the valence band, compared to 0.145 eV (0°K) as determined by Hall effect. Intense phonon replicas indicate that this acceptor is strongly cojpled to the lattice; the observed discrepancy in the ionization energies may therefore be caused by a Stokes shift. Cu introduced into acceptor‐doped GaAs under intrinsic conditions shows the same acceptor level, but this level is absent when Cu is diffused into extrinsic p GaAs. No luminescence is found which can be assigned to the interstitial Cu donor, possibly because this donor level is paired with the acceptor is 77°K. Diffusion of Cu into Te‐doped GaAs causes the shift of a luminescence band at 1.2–1.33 eV; this is interpreted as a transformation of a donor‐vacancy center into a donor—Cu center. Shallow acceptor levels at 0.020 and 0.027 eV are found in as‐grown GaAs. These levels are not caused by Cu but are attributable, respectively, to carbon and possibly to silicon introduced during crystal preparation.