NOVELTY - A gallium based crystal has primary thickness of single crystalline material comprising gallium and nitrogen having a surface region with m-plane orientation, and secondary thickness of single crystalline material deposited on surface region in m-plane. Primary thickness of single crystalline material has c-direction length of more than 1 cm and 30 cm or less and a-direction length of more than 1 cm and 30 cm or less. Secondary thickness of single crystal material comprises gallium and nitrogen, and has m-direction thickness of 25 micron or more and 50 mm or less.    USE - Gallium based crystal is used for fabrication of electrical and optical device (claimed). Uses include but are not limited to substrate for light emitting diode, laser diode, transistor, rectifier, thyristor, integrated circuit, photodetector, cascade switch and solar cell, and for photoelectrochemical water splitting for hydrogen generation.    ADVANTAGE - The large area crystals of non-polar or semi-polar material are economically grown. The substrate having high surface area is fabricated.    DETAILED DESCRIPTION - A gallium based crystal has a primary thickness of single crystalline material comprising gallium and nitrogen having a surface region with m-plane orientation, and a secondary thickness of single crystalline material deposited on the surface region in the m-plane. The primary thickness of single crystalline material has c-direction length of more than 1 cm and 30 cm or less and a-direction length of more than 1 cm and 30 cm or less. The primary thickness of crystalline material has m-direction thickness of 0.1-10 mm. The secondary thickness of single crystal material comprises gallium and nitrogen, and has m-direction thickness of 25 micron or more and 50 mm or less. The primary thickness and secondary thickness are free of stacking faults and coalescence fronts, and the total impurity concentration in the secondary thickness is more than that of primary thickness. INDEPENDENT CLAIMS are included for the following:    (1) gallium nitride thickness of material;    (2) method for slicing substrates;    (3) fabrication of seed crystal;    (4) fabrication of gallium based substrate;    (5) composite seed crystal;    (6) fabrication of electrical and optical devices; and    (7) fabrication of gallium containing substrate material.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view explaining formation of seed crystal.    Non-polar wafer (101)    Gallium nitride layer (103)