The CdTe semiconductor has been used for X- and γ-ray imaging detectors owing to its sensitivity to ionizing radiation, high energy and spatial resolution, and ability to operate at room temperature. However, it is challenging to grow large-diameter CdTe. Therefore, we aim to develop large-area high-resolution X-ray imaging sensors by tiling small CdTe wafers. Postprocessing, bonding, and tiling require the heating of detectors; therefore, it is important to develop high-thermal-tolerance radiation sensors. We have fabricated two types of In/CdTe/Au diode detector (with a Schottky barrier and a p–n junction) using identical crystals and the same technological procedures except laser irradiation, and examined their resistance to heat treatment. The diodes with an In/CdTe rectifying contact and a p–n junction, formed by the laser-induced backside doping of the CdTe subsurface layer with In, had similar electrical and spectral characteristics, which did not significantly change after heating at temperatures below the In melting point (156 ℃). The Schottky diodes, subjected to heating at 200 and 300 ℃, exhibited the deterioration of the electrical characteristics (reverse dark current increased) and lost their detection ability. In contrast, the p–n junction diodes demonstrated highly stable I–V characteristics, and the measured 241Am radioisotope emission spectra did not degrade even after melting and solidifying the In electrode.