Neutral manganese acceptor in GaP: An electron-paramagnetic-resonance study

In order to clarify the nature of the neutral Mn acceptor in GaP, we have carried out optical-absorption and electron-paramagnetic-resonance (EPR) experiments using both conventional and thermally detected EPR on semi-insulating GaP:Mn. In thermal equilibrium at low temperatures, all the manganese occurs in the charged acceptor state ${\mathrm{Mn}}_{\mathrm{Ga}}^{2+}$(${\mathit{A}}^{\mathrm{-}}$). By illumination with photon energies greater than 1.2 eV, it can be partially converted into the neutral charge state. The arising photostimulated EPR spectrum shows the characteristic of a tetragonally distorted center with an integer spin. The resonance lines are detectable only at temperatures below 7 K, and their linewidth of about 50 mT is due to the unresolved Mn-hyperfine splitting. We interpret the experimental data in terms of ${\mathrm{Mn}}_{\mathrm{Ga}}^{3+}$ ions on strain-stabilized sites of tetragonal symmetry due to a strong T⊗ε Jahn-Teller coupling within the ${}_{}{}^5{}_{}{}^{}$ ${\mathit{T}}_2$ ground state. Such a behavior is expected for a 3${\mathit{d}}^4$ defect, as observed for the isoelectronic impurity ${\mathrm{Cr}}^{2+}$ in GaAs, and other tetrahedrally coordinated semiconductors. The analysis of the EPR spectra thus verifies that, in GaP, the neutral charge state of the Mn acceptor is ${\mathrm{Mn}}_{\mathrm{Ga}}^{3+}$(${\mathit{A}}^0$) in contrast to its behavior in GaAs and InP. © 1996 The American Physical Society.