Asymmetric external field effects on photoluminescence efficiency in a blue (In,Ga)N quantum-well diode with an additional n -type electron reservoir layer

External field effects on photoluminescence (PL) spectra of a blue In_0.3Ga_0.7N multiple-quantum-well (MQW) diode with an additional n⁺-doped In_0.18Ga_0.82N electron reservoir layer (ERL) have been investigated at 20 K as a function of bias voltage under direct excitation conditions, where only the MQW and ERL regions are photoexcited. When the reverse bias is increased, the PL emission of MQW is strongly quenched, accompanying a blue-shift due to compensation of the internal piezo-fields, while the ERL emission is stable. However, the PL intensity of ERL is significantly decreased with increasing the forward field, showing asymmetric behaviors on the PL efficiency with respect to the field direction. These results indicate that field-induced escape processes of photogenerated electrons and holes from the excited regions play an important role for determination of the PL efficiency.