In and infrared (IR) wavelengths have recently drawn

In the field of photodetection,
ultraviolet (UV) and infrared (IR) wavelengths have recently drawn  considerable attention. It has been found that
UV and IR radiations available in space have a wide range of applications in advanced
optical communications and other emerging technologies7-9. Because of
high-sensitivity to UV and IR photons high interest has been focused on the
study of  III-nitride (III-N) material
system 10, 11. The wide bandgap of these materials paves a way for high- performance
UV and IR photodetectors to possess ultralow dark current and high temperature of
operation. Furthermore, the flexibility of employing band gap tailoring  for the III–N material system permits
selective photon detection of specific wave lengths in different UV and IR  bands, which offers further reduction in size and
cost in advanced UV and IR detection systems.


 A photo detector is a device which is capable
of converting light into either current or voltage based on its mode of
operation. In  the last few decades, different
types of III-N based photodetectors have been  studied and proposed12, this include Schottky
barrier diodes,15 metal-semiconductor-metal MSM photodetectors PDs, p-n junction
diodes13, p-i-n diodes14  and
avalanche photodiodes APDs16. For practical applications which very low signals
of light are detected, the use of photo detectors with inherent gain is
inevitable. Although the photoconductors and MSM PDs  exhibit internal gain, the magnitude of their  gains may not be sufficient enough to amplify the
signal to the required level and the photoconductive gain mechanism of these
devices,  responsible for the high
responsivity is a slow and noisy process. Furthermore, the optical gain that is
observed in devices is  caused  partly by defect-related effects and is,
therefore, very sensitive to nature and density of the defects  formed during the growth of the material and
device processing. 


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