The optical properties of Al-rich AlGaN/AlN quantum wells are assessed by excitation-power-dependent time-integrated (TI) and time-resolved (TR) photoluminescence (PL) measurements. Two excitation sources, an optical parametric oscillator and the 4th harmonics of a Ti:sapphire laser, realize a wide range of excited carrier densities between 1012 and 1021 cm−3. The emission mechanisms change from an exciton to an electron-hole plasma as the excitation power increases. Accordingly, the PL decay time is drastically reduced, and the integrated PL intensities increase in the following order: linearly, super-linearly, linearly again, and sub-linearly. The observed results are well accounted for by rate equations that consider the saturation effect of non-radiative recombination processes. Using both TIPL and TRPL measurements allows the density of non-radiative recombination centers, the internal quantum efficiency, and the radiative recombination coefficient to be reliably extracted.

Photoluminescence decay dynamics in an InGaN/GaN/AlGaN single quantum well

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We performed time‐resolved photoluminescence (TRPL) measurements for high‐quality Al‐rich AlGaN/AlN multiple quantum wells (MQWs) under selective excitation condition in order to investigate carrier recombination dynamics around the Mott transition. Fast and slow lifetime components (12 ps and 210 ps) were definitely observed under high excitation conditions at 5.5 K and were attributed to electron‐hole plasma and the exciton many‐body effect, respectively. It was found that the remarkable difference in the radiative lifetimes caused strongly excitation‐power dependent internal quantum efficiencies. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)