A three-dimensional (3-D) electrothermal model was developed to study the InP-based thin-film In0.53Ga0.47As/In0.52Al0.48As superlattice (SL) microrefrigerators for various device sizes, ranging from 40 x 40 to 120 x 120 mu m(2). We discussed both the maximum cooling and cooling power densities (CPDs) for experimental devices, analyzed their nonidealities, and proposed an optimized structure. The simulation results demonstrated that the experimental devices with an optimized structure can achieve a maximum cooling of 3 degrees C, or equivalently, a CPD over 300 W/cm(2). Furthermore, we found it was possible to achieve a maximum cooling of over 10 degrees C; equivalently, a CPD over 900 W/cm(2), when the figure of merit (ZT) of InGaAs/InAlAs SL was enhanced five times with nonconserved lateral momentum structures. Besides monolithic growth, we also proposed a fusion bonding scheme to simply bond the microrefrigerator chip on the back of the hot spots, defined as two-chip integration model in this paper. The cooling effect of this model was analyzed using ANSYS simulations.