Band
structure engineering based on InGaN/ZnGeN2 heterostructure
quantum wells (QWs) is proposed to address the long-standing charge
separation challenge in visible light emitters using polar InGaN QWs
as active media. A nanometer-scale layer of ZnGeN2 is successfully
incorporated in InGaN QWs via metalorganic chemical vapor deposition.
Understanding the structural properties of the heterostructure QWs
reveals that the growth conditions for the GaN barrier layers play
an important role in the QW properties. Specifically, the structural
quality of the QWs is improved by increasing the thickness and the
growth temperature of the GaN barrier layers. Due to the large band
offset at the InGaN/ZnGeN2 heterointerface, the position
and thickness of the ZnGeN2 sub-layer within the InGaN
QWs determine the potential minima and thus the carrier wave functions
in both conduction and valence bands. This work demonstrates the effectiveness
of emission wavelength tunability of InGaN/ZnGeN2/InGaN
heterostructure QWs via tuning of the ZnGeN2 sub-layer
properties. More significantly, the peak emission of InGaN/ZnGeN2/InGaN heterostructure QWs can be extended to longer wavelengths
without increasing the In composition or the QW thickness. Results
from this work provide a new route for addressing the low quantum
efficiency of conventional InGaN QWs emitting at green and longer
wavelengths.