TRACE COPPER MEASUREMENTS AND ELECTRICAL EFFECTS IN LPE HGCDTE

Recent improvements in sputter initiated resonance ionization spectros copy (SIRIS) have now made it possible to measure copper in HgCdTe fil ms into the low 10(13) cm(-3) range. We have used this technique to sh ow that copper is responsible for type conversion in n-type HgCdTe fil ms. Good n-type LPE films were found to have less than 1 x 10(14) cm(- 3) copper, while converted p-type samples were found to have copper co ncentrations approximately equal to the hole concentrations. Some comp ensated n-type samples with low mobilities have copper concentrations too low to account for the amount of compensation and the presence of a deep acceptor level is suggested. Tn order to study diffusion of cop per from substrates into LPE layers, a CdTe boule was grown intentiona lly spiked with copper at approximately 3 x 10(16) cm(-3). Annealing H gCdTe films at 360 degrees C was found to greatly increase the amount of copper that diffuses out of the substrates and a substrate screenin g technique was developed based on this phenomenon. SIRIS depth profil es showed much greater copper in HgCdTe films than in the substrates, indicating that copper is preferentially attracted to HgCdTe over Cd(Z n)Te. SIRIS spatial mapping showed that copper is concentrated in subs trate tellurium inclusions 5-25 times greater than in the surrounding CdZnTe matrix.