Simplified Analysis of Electron-Hole Recombination in Zn- and O-Doped GaP

An analysis of the recombination kinetics of three differently annealed GaP samples of a crystal doped with Zn and O is presented. The kinetics are described in terms of four parameters: a hole recombination lifetime $T_1$; an emission rate $e_1$ for electrons to be thermally excited from the Zn-O center back into the conduction band; a shunt-path lifetime $T_{\mathrm{SH}}$ and a rate $c_1$ for capture of electrons by the Zn-O centers. Rate $e_1$ had been previously determined by Jayson, Bachrach, Dapkus, and Schumaker. Two other parameters $T_1$ and ($T_{\mathrm{SH}}^{-1\mathrm{}}+c_1$) were directly measured. $T_{\mathrm{SH}}$ and $c_1$ were separately determined by evaluating the ratio $\frac{T_{\mathrm{SH}}^{-1\mathrm{}}}{(T_{\mathrm{SH}}^{-1\mathrm{}}+c_1)}$, which is the fraction of the carriers leaving the conduction band through the shunt path. This ratio was deduced in two independent ways from analysis of the time dependence of the red and green luminescence. In the most efficient sample, the parameters at 298 K were $e_1^{-1\mathrm{}}=220\mathrm{}\pm 10$ nsec, $T_1=630\mathrm{}\pm 30$ nsec, $T_{\mathrm{SH}}=60\mathrm{}\pm 10$ nsec, and $c_1^{-1\mathrm{}}=10\mathrm{}\pm 1$ nsec. About 0.60 ± 0.05 of the recombination in this sample was through the Zn-O centers. The measured radiative efficiency was 0.29 ± 0.03, indicating that about half the recombination was radiative. The radiative and nonradiative hole recombination times were ${\left(T_1\right)}_{\mathrm{rad}}=1310\mathrm{}\pm 130$ nsec and ${\left(T_1\right)}_{\mathrm{nonrad}}=1210\mathrm{}\pm 90$ nsec for this sample with $p\approx \frac{2\times {10}^{17}}{{\mathrm{cm}}^3}$ ($N_A-N_D=\frac{2.5\times {10}^{17}}{{\mathrm{cm}}^3}$). These lifetimes are in good agreement with those deduced previously by Jayson, Bhargava, and Dixon. The effect of annealing is to change $T_{\mathrm{SH}}$ from about 5 to 60 nsec and to increase the Zn-O center concentration by 5 or 6 times. These changes increased the recombination through the Zn-O...