Thermal analysis of InGaN/GaN (GaN substrate) laser diodes using transient interferometric mapping

Transient thermal behaviour and current distribution is investigated in InGaN/GaN blue lasers grown on GaN substrate. Back side transient interferometric mapping (TIM) method was applied for probing the temperature-induced phase shift due to increase in refractive index in the GaN laser ridge. The laser operates in a pulsed mode with pulse duration in the time scale from 300 ns to 2 μs. By using 2D thermal modeling, the comparison of the experimental and simulated phase shift allows to estimate a maximal temperature in the active region. The thermal mapping along the ridge reveals the inhomogeneity in the current flow attributed to substrate dopant distribution.