Comparative study of temperature-dependent electroluminescence efficiency in blue and green (In,Ga)N multiple-quantum-well diodes

Electroluminescence (EL) efficiency is comparatively investigated in the c-plane blue and green multiple-quantum-well (MQW) diodes over a wide temperature range (20-300 K) and as a function of injection current (0.01-10 mA). One striking result of the external quantum efficiency eta(ex) observed is that for the blue diode strong EL quenching can occur at temperatures below 100 K in agreement with the previous reports, while no significant EL collapse is seen below 100 K for the green MQW diode, especially at low injection currents. This means that the anomalous low temperature EL reduction observed for the blue (In,Ga)N MQW diode is not solely determined by temperature only but strongly modified by changing the In content in the active layers, suggesting mechanisms ruled by forward-bias dependent weaker carrier capture for the shallow potential depth MQW rather than hole freeze-out at deep Mg acceptors.