ELECTRICAL-ACTIVITY OF IODINE-DIFFUSED CDTE

The electrical activity of iodine in CdTe is discussed when iodine is introduced into the CdTe by diffusion from the vapour phase, It is com pared both with the total concentration of iodine in the diffused CdTe slices and with the electrical activity in CdTe slices which have bee n annealed under Cd- and Te-saturated vapour pressures, iodine-diffuse d slices of CdTe were profiled by secondary ion mass spectrometry (SIM S) to obtain the total iodine concentration and by capacitance-voltage (C-V) techniques to obtain the net concentration of electrically acti ve iodine, After annealing with iodine in the form of Cdl(2), the slic es were p-type, similar to those obtained when CdTe was annealed in ei ther excess Te or Cd vapour, and they showed no significant increase i n electrical activity, If Cd was added to the Cdl(2) diffusion source or the CdTe was given a subsequent anneal in cadmium vapour, the slice s became n-type, The results indicated that in all cases a neutral lay er composed of Cd(n)l(m) (m and n are integers) formed on the surface layers, whereas if Cd was involved in the diffusion, some of the iodin e existed in an electrically active form deeper into the slice with a maximum concentration of active carriers given by N-D-N-A approximate to 10(17) cm(-3). (C) 1997 by John Wiley & Sons Ltd.