GROWTH OF TIN-DOPED INDIUM-ANTIMONIDE FOR MAGNETORESISTORS

Magnetoresistors made from n-type indium antimonide are of interest fo r magnetic position sensing applications. In this study, tin-doped ind ium antimonide was grown by the metalorganic chemical vapor deposition technique using trimethylindium, trisdimethylaminoantimony, and tetra ethyltin in a hydrogen ambient. Using a growth temperature of 370 degr ees C and a pressure of 200 Torr, it was found that the electron densi ty in tin-doped films varied from 3.3 x 10(16) cm(-3) to 4.0 x 10(17) cm(-3) as the 5/3 ratio was varied from 4.8 to 6.8. From secondary ion mass spectroscopy (SIMS) studies, it was found that this variation is not caused by a change in site occupancy of the tin atoms from antimo ny to indium lattice sites, but rather to a change in the total tin co ncentration incorporated into the films. This dependence of tin incorp oration on stoichiometry could be used to rapidly vary the doping leve l during growth. Undoped films grown under similar conditions had elec tron densities of about 2 x 10(16) cm(-3) and electron mobilities near 50,000 cm(2)V(-1)s(-1) at room temperature for films that were only 1 .5 mu m thick on a gallium arsenide substrate. Attempts to grow indium antimonide at 280 degrees C resulted in p-type material caused by car bon incorporation. The carbon concentration as measured with SIMS incr eased rapidly with increasing growth rate, to above 10(19) cm(-3) at 0 .25 mu m/h. This is apparently caused by incomplete pyrolysis of a rea ctant at this low growth temperature. Growth at 420 degrees C resulted in rough surface morphologies. Finally, it was demonstrated that film s with excellent electron mobility and an optimized doping profile for magnetoresistors can be grown.