AlGaN is a promising material to develop UVLEDs and HEMT devices due to the direct wide-band gap material. In the
present investigation, AlxGa1-xN alloys were grown on c-plane sapphire substrate by MOCVD. Al content x was varied
in the composition range 0≤×≤0.6. The thickness and Al composition of the AlGaN was determined by HRXRD. The
growth rate decreases on increasing the composition of Al. The critical thickness of pseudomorphic AlGaN layer
decreases on increasing the composition. Thick layers resulted in cracks and it is important to grow thick layers with
high aluminum content free from crack for deep UV LEDs.
In the present investigation, AlxGa1-xN/AlyGa1-yN/AlxGa1-xN double heterostructures have been grown
on sapphire substrate using MOCVD. The active layer Al0.18Ga0.82N thickness has been changed as 14.8 nm and 23.4
nm by keeping the thickness of the Al0.45Ga0.55N barrier layer as constant. It has been found that full width halfmaxium
(FWHM) of (002) undoped GaN without double heterostructures as 352 arc-secs where as for the double
heterostructures it is found to be 523 and 483 arc-sec for the active layer thickness of 14.8nm and 23.4nm
respectively. The photon decay time was found to be 125, 85 and 87 ps for undoped GaN, Al0.18Ga0.82N of thickness
14.8 nm and 23.4 nm respectively using Time Resolved Photoluminescence (TRPL).It has been observed that the
well width has no effect on the radiative decay time which has been reported for the first time.
Group III-V nitrides have become versatile semiconducting materials for short wavelength LEDs, high
temperature transistors. The growth and device processing of these materials are significant due to unusually high
bond energies of nitrides. Inspite of high dislocations densities in the order of 109cm-2 the optical and electronic
devices based on nitrides show high performance compared to conventional semiconductor devices. Understanding
of the behavior of dislocations in these materials structures are very important for the fabrication of devices. In the
present study, GaN was grown on sapphire substrates using MOCVD. The dislocation density of GaN has been
estimated by wet etching and HRXRD. The results have been correlated with the growth conditions. The dislocation
density of the samples was found to be between 3.5x109cm-2 and 5.0x108cm-2.