Growth of tin-doped indium antimonide for magnetoresistors

Magnetoresistors made from n-type indium antimonide are of interest for magnetic position sensing applications. In this study, tin-doped indium antimonide was grown by the metalorganic chemical vapor deposition technique using trimethylindium, trisdimethylaminoantimony, and tetraethyltin in a hydrogen ambient. Using a growth temperature of 370 degrees C and a pressure of 200 Torr, it was found that the electron density 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 antimony to indium lattice sites, but rather to a change in the total tin concentration incorporated into the films. This dependence of tin incorporation on stoichiometry could be used to rapidly vary the doping level during growth. Undoped films grown under similar conditions had electron 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 carbon incorporation. The carbon concentration as measured with SIMS increased 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 reactant at this low growth temperature. Growth at 420 degrees C resulted in rough surface morphologies. Finally, it was demonstrated that films with excellent electron mobility and an optimized doping profile for magnetoresistors can be grown.