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In this paper, we describe the growth and characterization of 530-nm-thicksuperlattices (100 periods) of AlxGa1-xN/AlN (x = 0, 0.1) Stranski-Krastanovquantum dots for application as the active region of electron-beam pumpedultraviolet lamps. Highly dense (>10e11 cm-2) quantum dot layers are depositedby molecular beam epitaxy, and we explore the effect of the III/V ratio duringthe growth process on their optical performance. The study considers structuresemitting in the 244-335 nm range at room temperature, with a relative linewidthin the 6-11% range, mainly due to the QD diameter dispersion inherent inself-assembled growth. Under electron pumping, the emission efficiency remainsconstant for acceleration voltages below 9 kV. The correlation of thisthreshold with the total thickness of the superlattice and the penetrationdepth of the electron beam confirms the homogeneity of the nanostructures alongthe growth axis. Below the threshold, the emission intensity scales linearlywith the injected current. The internal quantum efficiency is characterized atlow injection, which reveals the material properties in terms of non-radiativeprocesses, and high injection, which emulates carrier injection in operationconditions. In quantum dots synthesized with III/V ratio < 0.75, the internalquantum efficiency remains around 50% from low injection to pumping powerdensities as high as 200 kW/cm2, being the first kind of nanostructures thatpresent such stable behaviour.

Internal quantum efficiency of AlGaN/AlN quantum dot superlattices for electron-pumped ultraviolet sources