  In this article, we show that the variation of the wavelength of a non-pumped
light-emitting diode (LED) is practically linear with temperature, a novel
consequence of Varshni's widely accepted empirical expression. This formula
models the bandgap variation for most semiconductors from 0K to their
high-temperature limits, subject to fitting parameters. Therefore, we suggest
an external thermal mechanism that can be used to tune the wavelength of a
constant-current biased LED and also to stabilize its wavelength. Furthermore,
we demonstrate the approach on published AlN data and show that the fitting
parameters follow trivially. In addition, we suggest a novel method to
characterize semiconductors. Finally, we present the results of experimental
measurements on several commercial LEDs.
