The present invention relates to the method for manufacturing an MSM photodetector using a HEMT structure incorporating a low-temperature grown semiconductor. The object of the present invention is to improve the speed characteristic of an MSM photodetector by using a HEMT structure incorporating a low-temperature grown semiconductor. The use of a HEMT structure incorporating a low-temperature grown semiconductor can reduce the number of holes reaching the metal electrode of MSM detectors, resulting in reduced hole current. As a result, the photocurrent response of the MSM detector using a HEMT structure incorporating a low-temperature grown semiconductor is dominated by electron current, resulting in a significant improvement in speed performance.