Herein, the designing principles of InAs based pBin mid-infrared (MWIR) photodetectors grown by liquid phase epitaxy (LPE) are presented based on the lattice mismatch. pBin MWIR detector structures with InAs, InAs0.94Sb0.06 and InAs0.89Sb0.11 absorbers were designed and grown by LPE, and then fabricated into mesa type detectors. Room temperature electrical performances of the three kinds of detectors were characterized. All three kinds of detectors achieved detectivities higher than 1 × 109 cm Hz1/2 W−1, and especially the detector with an InAs absorber further achieved a detectivity of 1.6 × 1010 cm Hz1/2 W−1 at 300 K, which is the highest ever reported, indicating good material qualities of the detectors.