We have investigated the fabrication and luminescent properties of different polymorphs of erbium (Er) silicate in Er-doped silicon oxide films. Silicon oxide films embedded with y-Er2Si2O7 and alpha-Er2Si2O7 layers have been fabricated with annealing at 1100 degrees C and 1150 degrees C, respectively. We demonstrate that y-Er2Si2O7 shows a stronger photoluminescence (PL) intensity, a longer PL lifetime, and a weaker PL thermal quenching effect than alpha-Er2Si2O7 due to the larger density of optically active Er ions, larger Er-Er average distance, higher symmetry, and stronger Er-O bonding. The Er lifetime-density product of y-Er2Si2O7 is as high as 3.5x10(18)scm(-3) and is at least 2.4 times as large as that of alpha-Er2Si2O7 making y-Er2Si2O7 an excellent candidate for high optical gain.