Degradation Mechanisms of InGaN Laser Diodes

We discuss various mechanisms of laser diode degradation based on our own experiments and on the available literature data. In most of the cases, degradation of InGaN laser diodes occurs through the increase of the threshold current with almost constant slope efficiency. The threshold current change follows frequently the square root on time dependence. Though this type of behavior has usually been attributed to magnesium acceptor diffusion, no firm proof of such a hypothesis has so far been presented. In contrast, there is an increasing number of reported experiments showing that the most important factor contributing to fast (hours), and medium time (hundreds of hours) degradation is the process of carbon deposition. This process involves photochemical reactions leading to the decomposition of hydrocarbons existing in the laser diode environment. This process resembles very closely the mechanism responsible for 980-nm laser diode degradation and known as Package Induced Failure.