Microscopic investigation of InGaN/GaN heterostructure laser diode degradation using Kelvin probe force microscopy

Abstract

We report on Kelvin probe force microscopy (KPFM) measurements on fresh and artificially aged InGaN/GaN laser test structures. In the case of an unbiased laser diode, a comparison of the surface potential between a fresh and a stressed laser diode shows a pronounced modification of the laser facet due to the aging process. Performing KPFM measurements under forward bias, a correlation between the macroscopic I–V characteristics and the microscopic voltage drop across the heterostructure layer sequence is found. This clearly demonstrates the potential of KPFM for investigating InGaN/GaN laser diode degradation.

Degradation of InGaN/GaN laser diodes investigated by micro-cathodoluminescence and micro-photoluminescence

“…These results have been obtained on laser diodes grown on GaN substrate: we expect the degradation mechanism described above to be present also in laser diodes grown on foreign substrates (e.g., on SiC, as those studied in Refs. 1 and 14), but with different kinetics (due to the different initial densities of defects 15 ).…”