EFFECT OF COOLING PROCEDURE AFTER ANNEALING ON ELECTRICAL-PROPERTIES OF CD0.2HG0.8TE EPITAXIAL-FILMS GROWN BY LIQUID-PHASE EPITAXY

Effect of cooling procedure after annealing on the electrical properti es of Cd0.2Hg0.8Te (CMT) epitaxial films grown by liquid phase epitaxy has been investigated to obtain the CMT films with low carrier concen tration of 10(14) cm(-3) reproducibly. Annealing has been performed at the temperature range from 260 to 350 degrees C for 8 h in a fixed Hg vapor pressure. The quenching and the gradual cooling over a duration of 200 min after annealing have been employed for the cooling procedu res. For quenched CMT samples, hole concentration decreases with decre asing anneal temperature and conduction type conversion from p to n is observed at 300 degrees C. For the gradual cooling, all samples show n-type conduction for all annealing temperatures. Electrical propertie s of annealed layers strongly depend on the cooling procedure. The dif ference in electrical properties of the annealed CMT between two types of cooling procedure is mainly attributed to the difference in the an nihilation of Hg vacancies during cooling procedure. The decrease of H g vacancies during quenching is negligible, while Hg vacancies are ann ihilated during gradual cooling by rapid Hg diffusion. The diffusion c oefficient of Hg is estimated more than 10(-9) cm(2)/s and this value is two orders of magnitude larger than that obtained by radiotracer te chnique.