Figure 1
From: Ultra-Broadband Optical Gain in III-Nitride Digital Alloys

Schematic illustration of (a) a quantum well active region and (b) a digital alloy active region. (c) Energy band lineup of individual quantum wells with different thickness and bandgap produce optical gain spectra that are spectrally separate with narrow bandwidth. (d) The energy band diagrams of a digital alloy active region with quantized minibands yields broadband optical gain spectrum produced by closely packed (in energy) interband transitions.