THERMAL DONOR FORMATION IN ALUMINUM-DOPED SILICON

Aluminum as a dopant has been reported to enhance thermal donor (TD) f ormation in silicon. We present results based upon infrared (IR) studi es of a recently discovered group of vibrational absorption bands rela ted to the TDs. According to these vibrational absorption bands three categories of TDs has been suggested to develop in the temperature ran ge 350-500 degrees C. Our results reveal that in comparison with dopan ts such as B and P the first category appearing is suppressed in Al-do ped samples while the second category is not affected. The formation o f the third category is enhanced in moderately (approximate to 1 x 10( 16) at. cm(-3)) Al-doped samples. A new IR absorptionband at 992 cm(-1 ) which is linearly correlated to the Al-doping concentration is found . It is suggested to originate from an oxygen vibration in a Si-O-Al c enter.