Semipolar substrates offer a number of advantages for UV emitting AlGaInN based laser diodes, including higher gain, an ability to operate with nearly transverse electric (TE) optical modes, and an ability to provide pseudo-substrates with tailorable lattice constants, something unavailable from bulk c-plane AlN substrates. When high aluminum content buffer layers are grown on semipolar bulk GaN substrates, strain relaxation via glide of threading dislocations forestalls cracking, with the MD segments constrained to the heterointerface, allowing subsequent growth of laser quality material. Al<SUB>x</SUB>Ga<SUB>1-x</SUB>N layers with 0.1 < x < 0.5 have been grown on (20-21) bulk GaN substrate by metal organic chemical vapor deposition (MOCVD). InGaN/GaN multiple quantum wells (MQW) were grown on top of 1.2 μm thick relaxed Al<SUB>0.22</SUB>GaN<SUB>0.78</SUB>N on (20-21) GaN and directly on GaN. While strained MQW on GaN clearly showed TDs from cathodoluminescence (CL), MQW on relaxed AlGaN showed dark lines, suggesting the generation of MDs and disappearance of TDs. As the aluminum composition in AlGaN increased, single Al<SUB>0.4</SUB>Ga<SUB>0.6</SUB>N layer started showing cracks along c-projection direction at about 300 nm. This could be due to too much strain and gliding of TDs is no loner enough to release the strain for high aluminum content AlGaN directly grown on GaN. We have also grown AlGaN on (20-21) GaN, step grading to higher aluminum composition. This allows relaxation of AlGaN without generation of new TDs, ultimately leading to high quality AlGaN template for laser diode growth. On-axis reciprocal space mapping of the graded AlGaN showed tilt at each interface associated with the presence of MDs. This is a clear indication of the relaxation of each AlGaN layer. When more than 1 μm thick Al<SUB>0.45</SUB>Ga<SUB>0.55</SUB>N layer was grown on the graded AlGaN, the crack healing was also observed. The diode operation of near UV light emitting diodes (λ~385 nm) on the relaxed buffer has been shown and is a promising result for device application of relaxed AlGaN template. In this study, we report on the growth of semipolar AlGaN with high aluminum content on bulk (20-21) semipolar GaN. Single AlGaN and step graded AlGaN layers were grown by MOCVD and characterized by various analytical techniques such as CL and x-ray diffraction to understand the relaxation mechanisms in semipolar AlGaN layer.