Material Gain Engineering in Staggered Polar AlGaN/AlN Quantum Wells Dedicated for Deep UV Lasers

Material gain is calculated for polar staggered AlxGa1-xN/AlN quantum wells (QWs) of various architectures: i) with a step-like AlyGa1-yN barrier grown prior the AlxGa1-xN QW, ii) with a step-like barrier grown on the QW, and iii) with a step-like barrier grown prior and on the QW. The obtained results are compared with those obtained for reference AlxGa1-xN/AlN QWs. With the increase in Al concentration in the reference QW the gain peak blueshifts and its strength decreases mainly due to the Al-related increase in the electron effective mass. The step-like barrier is able to tune the spectral position of the gain peak and enhance the gain strength. For the staggered QWs with step-like barriers grown prior to the QW a blueshift of the gain peak is observed while a redshift of the gain peak is observed for QWs with the step-like barrier grown on the QW. It is shown that a strong material gain in the 260-280 nm spectral range can be achieved with the staggered AlxGa1-xN/AlN QW with x = 30% and 1 nm thick step-like AlyGa1-yN barrier of high Al concentration (y = 0.7-0.9). The increase in Al concentration in the staggered QWs shifts the gain peak to deeper UV but the strength of material gain decreases.