  We have fabricated two-dimensional phononic crystal (PnC) structures on GaAs
doubly-clamped microelectromechanical system (MEMS) beam resonators to modulate
their thermal properties. Owing to the reduction in the thermal conductance of
the MEMS beams by introducing the PnC structures, the MEMS bolometers with the
PnC structures show 2-3 times larger thermal sensitivities than the unpatterned
reference sample. Furthermore, since the heat capacitance of the MEMS beams is
also reduced by introducing the PnCs, the thermal decay time of the patterned
MEMS beams is increased only by about 30-40 %, demonstrating the effectiveness
of the PnCs for enhancing the thermal sensitivities of bolometers without
significantly deteriorating their operation bandwidths.
