Effect of uniaxial stress on the excitonic molecule bound to nitrogen trap in GaP

We have investigated the experimental and theoretical stress dependence of the excitonic molecule bound to the isoelectronic nitrogen trap in GaP. Data have been collected at pumped-liquid-helium temperature for the stress directions [001], [111], and [110] respectively. The quantitative stress dependence is consistent with the identification previously reported by Merz et al. concerning the energy states of the complex. $A^{*}$ and $B^{*}$ photoluminescence lines result from the radiative recombination of an exciton constituting the excitonic molecule bound at a nitrogen atom. The ground states of the transition are the two $J=1\mathrm{}$ and $J=2\mathrm{}$ states of the single bound exciton. The intervalley-coupling matrix element $\Delta$ appears to be much smaller for the bound excitonic molecule than for the single bound exciton. We find $\Delta =2.3\mathrm{}$ meV for the bound excitonic molecule compared with $\Delta =8\mathrm{}$ meV for the single bound exciton.