Dislocation-enhanced diffusion in heteroepitaxial GaInP/InP:S

We characterize sulfur diffusion from heavily doped (n/spl sim/10/sup 19/ cm/sup -3/) InP:S (001) substrates into nominally undoped Ga/sub x/In/sub 1-x/P (0/spl les/x/spl les/0.2) epilayers during growth by low-pressure MOCVD. The composition, relaxation and dislocation density of the samples have been studied by high resolution X-ray diffraction and in-depth doping profiles have been obtained using a C-V electrochemical profiler. The analysis of these profiles shows that as the Ga content of these thick (/spl sim/1 /spl mu/m) samples is increased, a rapid enhancement of the sulfur diffusion from the substrate is observed. This enhancement is a consequence of the generation of an increasing number of dislocations initially caused by the mismatch. The structural defects act as pipes inside which the diffusion coefficient (D/sub d/) of sulfur atoms is calculated to be 6 orders of magnitude higher than that of the undislocated material (D/sub l/). Value of D/sub lspl sim/2/spl times/10/sup -17/ cm/sup 2s at the growth temperature of 640/spl deg/C have been deduced.<>