On the relation between electrical and electro-optical properties of tunnelling injection quantum dot lasers

We present a comprehensive study of the temperature dependent electronic and optoelectronic properties of a tunnelling injection quantum dot laser. The optical power-voltage (P _opt-V) characteristics are shown to be correlated with the current-voltage (I-V) and capacitance-voltage (C-V) dependencies at low and elevated temperatures. Cryogenic temperature measurements reveal a clear signature of resonant tunnelling manifested in periodic responses of the I-V and P _opt-V characteristics, which diminish above 60 K. The C-V characteristics reveal a hysteresis stemming from charging and de-charging of the quantum dots, as well as negative capacitance. The latter is accompanied by a clear peak that appears at the voltage corresponding to carrier clamping, since the clamping induces a transient-like effect on the carrier density. C-V measurements lead also to a determination of the dot density which is found to be similar to that obtained from atomic force microscopy. C-V measurements enable also to extract the average number of trapped electrons in each quantum dot which is 0.95. As the important parameters of the laser have signatures in the electrical and electro-optical characteristics, the combination serves as a powerful tool to study intricate details of the laser operation.