ELECTRON-BEAM CHARGING THERMOGRAPHY OF MIRRORS OF SEMICONDUCTOR-LASERDIODES

Charging insulating films in a scanning electron-microscope is shown t o be a potentially useful, thermographic technique which makes it, pos sible to reveal hot regions in microelectronic devices, with a spatial resolution in the submicrometer range. This technique entails deposit ing an insulating film on the device to ser-ve as thermographic medium . A focused, low-energy electron beam charges the insulator during the scanning process. Hot regions modify the local charge, which in turn modifies the secondary electron signal and thus generates a thermal co ntrast. This technique has been applied to investigate mirrors of GaAs /AlGaAs graded index separate confinement single quantum well laser di odes. Thermographic images of these mirrors have been obtained with a spatial resolution of 0.25 mum. Since the thermal images can be observ ed using the scanning electron microscope's TV mode, the course of fas t thermal phenomena at laser mirrors can be imaged. As an example, the thermal drift prior to the thermal runaway at laser mirrors has been investigated.