NOVELTY - A Group-III nitride based semiconductor device (800), comprises: a first layer (802) that is semipolar/nonpolar III-nitride layer (812) having lattice constant that is partially/fully relaxed, deposited on substrate (804)/template, where there are dislocations (806) at heterointerface between first layer and substrate/template; strain compensated layers on first layer, for defect reduction and stress engineering in device, that are lattice matched to larger lattice constant of first layer; and semipolar/nonpolar (AlInGaN)/III-nitride device layers on strain compensated layers.    USE - As Group-III nitride based semiconductor device, preferably a light emitting diode (LED), an electronic device including a transistor, (claimed) or solar cell.    ADVANTAGE - The device achieves higher efficiency light emitting devices (e.g. light emitting diodes (LEDs), laser diodes (LDs)), especially when combined with partially or completely relaxed buffer layers; and avoids AlInN or AlInGaN cladding; and reduces threading defect concentrations.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for fabricating aluminum-indium-gallium-nitride (AlInGaN) or Group-III nitride based semiconductor device, involving: growing a first layer that is a semipolar or nonpolar Group-III nitride (AlInGaN) layer having a lattice constant that is partially or fully relaxed, on a substrate or a template, where there are at least one dislocation at a heterointerface between the first layer and the substrate or the template; growing at least one strain compensated layers on the first layer, lattice matched to a larger lattice constant of the first layer, for defect reduction and stress engineering in the device; and growing at least one semipolar or nonpolar (AlInGaN) or Group-III nitride device layers on the strain compensated layers.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a semiconductor device.    Semiconductor device (800)    First layer (802)    Substrate (804)    Dislocation (806)    Heterointerface (808)    Strain compensated layers (810)    Semipolar or nonpolar III-nitride layers (812)    Semi-polar III-nitride light emitting active layer (814)    Aluminum-gallium-nitride electron blocking layer (816)