  Miniaturized, low-cost wavelength detectors are gaining enormous interest as
we step into the new age of photonics. Incompatibility with integrated circuits
or complex fabrication requirement in most of the conventionally used filters
necessitates the development of a simple, on-chip platform for easy-to-use
wavelength detection system. Also, intensity fluctuations hinder precise, noise
free detection of spectral information. Here we propose a novel approach of
utilizing wavelength sensitive photocurrent across semiconductor
heterojunctions to experimentally validate broadband wavelength detection on an
on-chip platform with simple fabrication process. The proposed device utilizes
linear frequency response of internal photoemission via 2-D electron gas in a
ZnO based heterojunction along with a reference junction for coherent common
mode rejection. We report sensitivity of 0.96 uA/nm for a broad
wavelength-range of 280 nm from 660-940 nm. Simple fabrication process,
efficient intensity noise cancelation along with heat resistance and radiation
hardness of ZnO makes the proposed platform simple, low-cost and efficient
alternative for several applications such as optical spectrometers, sensing and
IOTs.
