Sub-250 nm light emission and optical gain in AlGaN materials

We investigate the deep-UV optical emission and gain properties of AlxGa1−xN/AlyGa1−yN multiple quantum wells structures. These structures were grown by plasma-assisted molecular-beam epitaxy on 6H-SiC substrates, under a growth mode which promotes various degrees of band-structure potential fluctuations in the form of cluster-like features within the wells. The degree of inhomogeneities in these samples was determined by cathodoluminescence mapping. We measured the TE-polarized amplified spontaneous emission in the sample with cluster-like features and quantified the optical absorption/gain coefficients and gain spectra by the variable stripe length technique under ultrafast optical pumping. A maximum net modal gain of about 120 cm−1 is measured at 4.9 eV. On the other hand, we found that samples with homogeneous quantum wells lead to absorption. Numerical simulations are performed to support our experimental findings.