Laser generated (Al, Ga)As microstructures with high luminescence efficiency

New luminescence centers can be generated by irradiating AlxGa1-xAs structures with focused light from a cw Kr-ion laser operated at 647 nm. The luminescence centers were generated at a laser power density of 0.5 MW/cm². Regions as small as 0.8 µm wide and 0.2 µm thick were generated. The new luminescence centers are characterized by a high photoluminescence efficiency at room temperature and an emission energy 90-140 meV below the band-to-band recombination. They are of permanent nature: No changes in the emission spectrum or in the efficiency could be observed, if processed samples were subjected to heating cycles of up to 420 °C. Edge emitting LED´s have been prepared from laser processed (Al,Ga)As heterostructure material. In the laser processed regions the diodes exhibit a light yield within the new luminescence band which is more than quadrupled at low currents. The light output decreases to values below the band-to-band recombination at densities above 2.0 kA/cm².