The lifetime and the spin relaxation time of excited electrons in GaAs micr
otips tailored for scanning tunneling microscope (STM) with spin polarizati
on detection were measured by time-resolved polarized photoluminescence at
room temperature. The electron lifetime obtained from the tip-fabricated p-
type GaAs substrate was about 20 ps shorter than that obtained from the GaA
s substrate without microtips. This is attributed to the enhanced surface r
ecombination in the microtip. The spin relaxation time was comparable to th
e electron lifetime for the tip-fabricated GaAs substrate. From electron li
fetime and spin relaxation time, a respectable spin polarization of about 2
0% was evaluated in the tip-fabricated GaAs substrate, which was about 1.2
times larger than that in the GaAs substrate without microtips, under the 0
degrees incident angle of the excitation light. The influence of oblique i
ncidence of the excitation light is also discussed.