Ultrafast valence intersubband hole relaxation in InGaN multiple-quantum-well laser diodes

The ultrafast carrier dynamics in InGaN multiple-quantum-well (MQW) laser diodes were investigated using a time-resolved bias-lead monitoring technique. From the optical selection rules of TE and TM polarized light, one can selectively excite and probe different valence-subband-to-conduction-subband transitions in the MQW structure with different polarized pump and probe light. The subband structure of the MQW structure of the laser diode was calculated and is verified by electroluminescence measurement. Using this technique, ultrafast valence intersubband hole relaxation processes (τ<0.35 ps) were found to dominate the observed carrier dynamics.