Kinetics of recombination in nitrogen-doped GaP

Abstract

The doping dependence of the bulk efficiency for both n- and p-type GaP:N has been investigated experimentally and theoretically. Experimental data are presented for p-type Zn,N-doped, n-type Te,N-doped, and n-type S,N-doped GaP over a majority-carrier range 5×1016−2×1018 cm−3. The efficiency data and photoluminescent decay time data on the same samples are compared to a simple equilibrium model for the recombination kinetics in nitrogen-doped GaP. The model predicts that the efficiency should scale linearly with the minority-carrier lifetime, majority-carrier concentration, and the nitrogen concentration in the doping range considered. The comparison of the theoretical results with the experimental data shows that the bulk efficiency of p-type material agrees quantitatively with the analytical prediction. For Te- and S-doped material, which have widely different and varying minority-carrier lifetimes, the bulk efficiency of n-type material is shown to depend linearly upon the minority-carrier lifetime over the entire doping range considered. However, the normalized efficiency η/τmc is shown to depend upon the net donor concentration as η/τmc∝(ND-NA)0.5−0.6 above ND−NA≈3×1016 cm−3, independent of the donor, rather than linearly as predicted by theory. This deviation from theory remains unexplained. The data and analysis suggest that screening is of little importance over the doping rane considered. The lower limit on the nonradiative Auger lifetime of the bound excitons in p-type material is determined to be τxA≥(100−200)(1017cm−3/p) nsec. The strong variation of the minority-carrier lifetime with doping for n-type material is attributed to nonradiative centers extrinsic to the nitrogen center because of the different dependences observed for S- and Te-doped material and no firm conclusion can be drawn about the strength of nonradiative Auger recombination.