Thermionic emission of carriers in InGaN/(In)GaN multiple quantum wells

The room temperature photoluminescence (PL) intensity of In_xGa_1-xN/In_yGa_1-yN multiple quantum wells were correlated with the structural properties such as polarization strength and ground-state quantum levels for the triangular quantum wells. For x - y ≤ 0.2, the PL intensity increased with increasing the In-content of the well. In this region, we found that the PL intensity can be well described by the thermionic emission process with an activation energy corresponding to the energy difference between the valence band of barrier and the quantum level of holes in the well at the well/barrier interface. The pre-factor of the exponential component of effective barrier, reflecting the effective density of nonradiative recombination centers in the barriers, was 3.7 times larger for the samples with GaN barriers than that with InGaN barriers, indicating that the PL intensity is also influenced by the optical quality of barriers when the effective barrier height is relatively low.