The inventive methods of making a semiconductor device, e.g., a laser, comprise thermal (e.g., 3-5 .mu.m wavelength) imaging of a powered, partially completed device. The thermal image is obtained with apparatus that is capable of forming a substantially diffraction-limited image on a sensor array with an acquisition time of no more than 0.1 seconds, preferable no more than 0.01 seconds. In preferred embodiments, the image has temperature resolution of 0.01.degree. C. or better. Exemplary apparatus is disclosed. The inventive method facilitates, for instance, early identification of devices that are likely to fail lifetime requirements.