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

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 and forward bias conditions. The PL spectra were measured at 20 K under excitation photon energies above and below the bandgap energy of GaN barrier layers. The PL spectra under both excitation conditions show green emission from the (In,Ga)N SQW layer. The wavelength-integrated PL intensity changes drastically 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 significant reduction of the PL intensity is observed with further increase of the forward bias voltage. On the other hand, for the excitation above the bandgap energy of GaN (indirect excitation), the PL intensity rapidly increases up to +2 V, decreases once, increases again with the maximum value at +3.25 V, and drastically decreases again. These differences of the PL intensity variation reflect carrier escape and capture processes. That is, for the direct excitation condition, the PL intensity variation indicates the effect of the electric field on the radiative recombination and the carrier escape processes. In contrast, for the indirect excitation condition, it indicates the carrier transfer and capture processes. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)