Thermal mapping of transistors with a laser scanner

An active near-infrared laser scanner has been used to electronically map the temperature variations over the active regions of silicon interdigitated UHF transistors operating in the hot-spot regime. The principle makes use of the increase in electron-hole pair generation by the absorbed laser light with increasing temperature. The regions of enhanced photoresponse are displayed on a cathode-ray-tube display screen. Extensions to other devices and operating conditions, other than those which result in hot-spot operation, are suggested.