Spin-flip Raman scattering studies of post-growth annealed p-type nitrogen-doped zinc selenide

Spin-flip Raman scattering (SFRS) studies of post-growth annealed p-type nitrogen-doped zinc selenide grown by photoassisted metallo-organic vapour phase epitaxy (MOVPE) are presented. Four pieces from the same parent structure were subjected to annealing times between O and 60 min in a nitrogen atmosphere at a temperature of 500°C. The changes in net nitrogen acceptor concentration were determined via capacitance-voltage measurements and the samples studied by photoluminescence and SFRS. The results indicate that an annealing time of 30 min yields the greatest net acceptor concentration. However, whilst the sample annealed for this time showed the strongest SFRS signals due to neutral acceptors, it also gave the strongest SFRS signal from the deep donors that act as compensating centres. The results suggest that the number of active acceptors increases initially on annealing but decreases as annealing continues; it also appears that the concentration of acceptors cannot be raised by annealing without a simultaneous increase in the concentration of the deep donors. The behaviour can be accounted for by the activation (at short annealing times) of acceptors which were passivated by hydrogen during growth and (at longer annealing times and higher annealing temperatures) by the diffusion of defects.