  There is a lack of highly efficient light emitting devices (LEDs) operating
in the green spectral regime. The devices based on (In,Al)GaN show extremely
high efficiencies in violet and blue colors but fall short for longer emission
wavelengths due to the quantum confined Stark effect (QCSE). In this paper we
present a design of the active region based on wide InGaN quantum wells (QWs)
which do not suffer from QCSE and profit from an enhancement in the internal
quantum efficiency (IQE). The design exploits highly efficient optical
transitions between excited states. It is shown that, counterintuitively, the
devices with higher InGaN composition exhibit a higher enhancement in IQE.
Experimental evidence is provided showing a gradual change in the nature of the
optical transition with increasing thickness of the QW. Moreover, optical gain
in long wavelength LDs incorporating standard and wide QWs is investigated to
show the utilization of our concept.
