Carrier capture and escape processes in (In,Ga)N singlequantum-well diode under forward bias condition by photoluminescence spectroscopy

摘要

Carrier capture and escape processes in the super-bright green (In,Ga)N single-quantum-well (SQW)light-emitting diode (LED) has been studied by photoluminescence (PL) spectroscopy under reverse andforward bias conditions. The PL spectra were measured at 20 K under excitation photon energies aboveand below the bandgap energy of GaN barrier layers. The PL spectra under both excitation conditionsshow green emission from the (In,Ga)N SQW layer. The wavelength-integrated PL intensity changesdrastically depending on the applied bias voltage. For the excitation below the bandgap energy of GaN(direct excitation), the PL intensity increases with increasing the forward bias voltage up to +2 V and significantreduction of the PL intensity is observed with further increase of the forward bias voltage. On theother hand, for the excitation above the bandgap energy of GaN (indirect excitation), the PL intensity rapidlyincreases up to +2 V, decreases once, increases again with the maximum value at +3.25 V, and drasticallydecreases again. These differences of the PL intensity variation reflect carrier escape and captureprocesses. That is, in the direct excitation condition, the PL intensity variation indicates the effect of theelectric field on the radiative recombination and the carrier escape processes. In contrast, in the indirectexcitation condition, it is reflected in the carrier transfer and capture processes.