Nanocavities in He implanted InP

The formation of nanocavities in InP(001) by room-temperature He implantation and subsequent thermal annealing was studied using a combination of high-resolution x-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (XTEM) analyses. The nanocavities size and depth distributions were measured as a function of He ion dose phi(He) (1x10(16) to 9x10(16) cm(-2)) and ion energy E (25 to 70 keV), as well as annealing temperature T-a (600 to 750 degreesC) and time t(a) (5 to 25 min). HRXRD scans from annealed samples indicate an expansion of the InP lattice, contrary to what is usually observed following heavy-ion implantation. The critical phi(He) and T-a values for the formation of nanocavities were found by XTEM analysis to be between 1 and 2x10(16) cm(-2) and between 600 and 620 degreesC, respectively. Cavities of diameter 4-50 nm with {110}, {101}, and {001} facets were obtained. Increasing T-a and t(a) resulted in larger cavities and increasing phi(He) produced a larger number of cavities. Furthermore we find that nanocavities are metastable as their size first increases with annealing temperature and time but then decreases until they disappear for t(a)>25 min at T-a=640 degreesC or t(a)>10 min at T-a=750 degreesC. Results are compared with similar work carried out on He-implanted silicon and differences between the two materials are explained in terms of defect diffusivity and surface energy, higher diffusivity enhancing cavity collapse and lower surface energy enhancing cavity growth. (C) 2003 American Institute of Physics.